| 1. |
- Abrahamsson, Victor, et al.
(författare)
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Supercritical fluid extraction of lipids from linseed with on-line evaporative light scattering detection.
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 853, s. 320-327
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Tidskriftsartikel (refereegranskat)abstract
- Supercritical fluid extraction (SFE) is a green alternative method of extraction for neutral lipids in seeds compared to conventional methods utilizing organic solvents. In this work, a novel method where SFE is hyphenated with an evaporative light scattering detector is presented. The method was subsequently applied to determine lipid content in crushed linseed. The new method enables rapid quantification of extracted lipids as well as be ability to continuously monitor the extraction rate in real-time, thus being able to determine the time point of completed extraction. Both the detector and the method was validated. The results show that any of several tested oils can be used to calibrate the detection method for the determination of lipids extraction from linseed. The overall method repeatability and intermediate precision was 2.6% relative standard deviations. The extracted amount was significantly less than that obtained using the standard method of Soxhlet with petroleum ether, 26.0±0.4% (95% CI, n=9) compared to 32.3±1.3% (95% CI, n=3) of extracted amounts. It was found that channeling effects were present, and by either performing sequential repeated extractions with decompression in-between or by using a relatively large vessel a more complete extraction could be obtained. Interestingly, a substantially higher extracted amount (approximately 50%) was obtained compared to both a single extraction by SFE and the Soxhlet method. Therefore, it is recommended that an additional extraction including a rapid decompression in-between should be included in the validation of a method using supercritical fluid extraction, in order to either rule out channeling effects or to acquire a full recovery.
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| 2. |
- Ahmadi, Mazaher, et al.
(författare)
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Nanomaterials as sorbents for sample preparation in bioanalysis : A review
- 2017
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 958, s. 1-21
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Forskningsöversikt (refereegranskat)abstract
- In recent years, application of nanomaterials as sorbent has gained the attention of researchers in bioanalysis. Different nanomaterials have been utilized as the sorbent in extraction techniques such as solid phase extraction, dispersive solid phase extraction, magnetic solid phase extraction, microextraction by packed sorbent, solid phase microextraction, dispersive pt-solid phase extraction, and stir bar sorptive extraction. In the present review, different nanomaterials which have recently been utilized as sorbent for bioanalysis are classified into six main groups, namely metallic, metallic and mixed oxide, magnetic, carbonaceous, silicon, and polymer-based nanomaterials. Application of these nanomaterials in different extraction techniques for bioanalysis has been reviewed. This study shows that magnetic nanomaterials have gained significant attention owing to their magnetic separation ability. In addition, the present review shows that there is a lack in the application of nanomaterials for on-line analysis procedures, most probably due to some intrinsic properties of nanomaterials such as spontaneous agglomeration.
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| 3. |
- Ali Soomro, Razium, et al.
(författare)
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Highly sensitive determination of atropine using cobalt oxide nanostructures: Influence of functional groups on the signal sensitivity
- 2016
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Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 948, s. 30-39
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Tidskriftsartikel (refereegranskat)abstract
- This study describes sensitive determination of atropine using glassy carbon electrodes (GCE) modified with Co3O4 nanostructures. The as-synthesised nanostructures were grown using cysteine (CYS), glutathione (GSH) and histidine (HYS) as effective templates under hydrothermal action. The obtained morphologies revealed interesting structural features, including both cavity-based and flower-shaped structures. The as-synthesised morphologies were noted to actively participate in electro-catalysis of atropine (AT) drug where GSH-assisted structures exhibited the best signal response in terms of current density and over-potential value. The study also discusses the influence of functional groups on the signal sensitivity of atropine electro-oxidation. The functionalisation was carried with the amino acids originally used as effective templates for the growth of Co3O4 nanostructures. The highest increment was obtained when GSH was used as the surface functionalising agent. The GSH-functionalised Co3O4-modified electrode was utilised for the electro-chemical sensing of AT in a concentration range of 0.01 -0.46 mu M. The developed sensor exhibited excellent working linearity (R-2 = 0.999) and signal sensitivity up to 0.001 mu M of AT. The noted high sensitivity of the sensor is associated with the synergy of superb surface architectures and favourable interaction facilitating the electron transfer kinetics for the electro-catalytic oxidation of AT. Significantly, the developed sensor demonstrated excellent working capability when used for AT detection in human urine samples with strong anti-interference potential against common co-existing species, such as glucose, fructose, cysteine, uric acid, dopamine and ascorbic acid. (C) 2016 Elsevier B.V. All rights reserved.
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| 4. |
- Antfolk, Maria, et al.
(författare)
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Continuous flow microfluidic separation and processing of rare cells and bioparticles found in blood – A review
- 2017
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 965, s. 9-35
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Forskningsöversikt (refereegranskat)abstract
- Rare cells in blood, such as circulating tumor cells or fetal cells in the maternal circulation, posses a great prognostic or diagnostic value, or for the development of personalized medicine, where the study of rare cells could provide information to more specifically targeted treatments. When conventional cell separation methods, such as flow cytometry or magnetic activated cell sorting, have fallen short other methods are desperately sought for. Microfluidics have been extensively used towards isolating and processing rare cells as it offers possibilities not present in the conventional systems. Furthermore, microfluidic methods offer new possibilities for cell separation as they often rely on non-traditional biomarkers and intrinsic cell properties. This offers the possibility to isolate cell populations that would otherwise not be targeted using conventional methods. Here, we provide an extensive review of the latest advances in continuous flow microfluidic rare cell separation and processing with each cell's specific characteristics and separation challenges as a point of view.
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| 5. |
- Arrhenius, Karine, et al.
(författare)
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Suitability of different containers for the sampling and storage of biogas and biomethane for the determination of the trace-level impurities - A review
- 2016
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 902, s. 22-32
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Forskningsöversikt (refereegranskat)abstract
- The traceable and accurate measurement of biogas impurities is essential in order to robustly assess compliance with the specifications for biomethane being developed by CEN/TC408. An essential part of any procedure aiming to determinate the content of impurities is the sampling and the transfer of the sample to the laboratory. Key issues are the suitability of the sample container and minimising the losses of impurities during the sampling and analysis process. In this paper, we review the state-of-the-art in biogas sampling with the focus on trace impurities. Most of the vessel suitability studies reviewed focused on raw biogas. Many parameters need to be studied when assessing the suitability of vessels for sampling and storage, among them, permeation through the walls, leaks through the valves or physical leaks, sorption losses and adsorption effects to the vessel walls, chemical reactions and the expected initial concentration level. The majority of these studies looked at siloxanes, for which sampling bags, canisters, impingers and sorbents have been reported to be fit-for-purpose in most cases, albeit with some limitations. We conclude that the optimum method requires a combination of different vessels to cover the wide range of impurities commonly found in biogas, which have a wide range of boiling points, polarities, water solubilities, and reactivities. The effects from all the parts of the sampling line must be considered and precautions must be undertaken to minimize these effects. More practical suitability tests, preferably using traceable reference gas mixtures, are needed to understand the influence of the containers and the sampling line on sample properties and to reduce the uncertainty of the measurement.
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| 6. |
- Balgoma, David, et al.
(författare)
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Modeling the fragmentation patterns of triacylglycerides in mass spectrometry allows the quantification of the regioisomers with a minimal number of standards
- 2019
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1057, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometry allows the relative quantification of the regioisomers of triacylglycerides by the calibration of their fragmentation patterns. However, due to the plethora of regioisomers of triacylglycerides, calibration with every standard is not feasible. An analytical challenge in the field is the prediction of the fragmentation patterns of triacylglycerides to quantify their regioisomers. Thus, we aimed to model these fragmentation patterns to quantify the regioisomeric composition, even for those without commercially available standards. In a first step, we modeled the fragmentation patterns of the regioisomers of triacylglycerides obtained from different published datasets. We found the same qualitative trends of fragmentation beyond differences in the type of adduct in these datasets (both [M+NH4]+ and [M+H]+), and the type of instrument (orbitrap, Q-ToF, ion-trap, single quadrupole, and triple quadrupole). However, the quantitative trends of fragmentation were adduct and instrument specific. From these observations, we modeled quantitatively the common trends of fragmentation of triacylglycerides in every dataset. In a second step, we applied this methodology on a Synapt G2S Q-ToF to quantify the regioisomers of triacylglycerides in sunflower and olive oils. The results of our quantification were in good agreement with previous published quantifications of triacylglycerides, even for regioisomers that were not present in the training dataset. The species with more than two highly unsaturated fatty acids (arachidonic, eicosapentaenoic, and docosahexaenoic acids) showed a complex behavior and lower predictability of their fragmentation patterns. However, this framework presents the capacity to model this behavior when more data are available. It would be also applicable to standardize the quantification of the regioisomers of triacylglycerides in an inter-laboratory ring study.
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| 7. |
- Barrera, J., et al.
(författare)
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A new plastic scintillation resin for single-step separation, concentration and measurement of technetium-99
- 2016
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 936, s. 259-266
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Tidskriftsartikel (refereegranskat)abstract
- Technetium is a synthetic element with no stable isotopes, produced as waste in nuclear power plants and in cyclotrons used for nuclear medicine. The element has high mobility, in the form of TcO4 −; its determination is therefore important for environmental protection. Technetium is found in low concentrations and therefore common methods for its analysis include long treatments in several steps and require large amounts of reagents for its purification and preconcentration. Plastic scintillation resins (PSresin) are novel materials used to separate, preconcentrate and measure radionuclides in a single step. The objective of this study is to prepare and characterise a PSresin for the preconcentration and measurement of 99Tc. The study first evaluates the reproducibility of the production of PSresins between batches and over time; showing good reproducibility and storage stability. Next, we studied the effect of some common non-radioactive interferences, showing small influences on measurement, and radioactive interferences (36Cl and 238U/234U). 36Cl can be removed by a simple treatment with 0.5 M HCl and 238U/234U can be removed from the column by cleaning with a mixture of 0.1 M HNO3 and 0.1 M HF. In the latter case, a slight change in the morphology of the PSresin caused an increase in detection efficiency. Finally, the PSresin was applied to the measurement of real spiked samples (sea water and urine) with deviations lower than 10% in all cases.
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| 8. |
- Beech, Jason P., et al.
(författare)
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Separation of pathogenic bacteria by chain length
- 2018
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1000, s. 223-231
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Tidskriftsartikel (refereegranskat)abstract
- Using Deterministic Lateral Displacement devices optimized for sensitivity to particle length, we separate subpopulations of bacteria depending on known properties that affect their capability to cause disease (virulence). For the human bacterial pathogen Streptococcus pneumoniae, bacterial chain length and the presence of a capsule are known virulence factors contributing to its ability to cause severe disease. Separation of cultured pneumococci into subpopulations based on morphological type (single cocci, diplococci and chains) will enable more detailed studies of the role they play in virulence. Moreover, we present separation of mixed populations of almost genetically identical encapsulated and non-encapsulated pneumococcal strains in our device.
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| 9. |
- Cavanillas, Santiago, et al.
(författare)
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A self-polishing platinum ring voltammetric sensor and its application to complex media
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier Masson. - 0003-2670 .- 1873-4324. ; 859, s. 29-36
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Tidskriftsartikel (refereegranskat)abstract
- A self-polishing voltammetric sensor was recently developed and has been applied to samples of urea, milk and sewage water. The polishing device continuously grinds a platinum ring electrode, offering a reproducible and clean electrode surface. Principal component analysis (PCA) and partial least squares (PLS) techniques were applied to interpret the data and to build prediction models. In an evaluation of samples with different urea concentrations, the grinding step allows for repeatable measurements, similar to those after electrochemical cleaning. Furthermore, for the determination of sewage water concentrations in drinking water and for the evaluation of different fat contents in milk samples, the polishing eliminates sensor drift produced by electrode fouling. The results show that the application of a self-polishing unit offers a promising tool for electrochemical studies of difficult analytes and complex media. (C) 2014 Elsevier B.V. All rights reserved.
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| 10. |
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| 11. |
- Chen, Chang, et al.
(författare)
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Untargeted screening of unknown xenobiotics and potential toxins in plasma of poisoned patients using high-resolution mass spectrometry: Generation of xenobiotic fingerprint using background subtraction
- 2016
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Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 944, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- A novel analytical workflow was developed and applied for the detection and identification of unknown xenobiotics in biological samples. High-resolution mass spectrometry (HRMS)-based data-independent MSE acquisition was employed to record full scan MS and fragment spectral datasets of test and control samples. Then, an untargeted data-mining technique, background subtraction, was utilized to find xenobiotics present only in test samples. Structural elucidation of the detected xenobiotics was accomplished by database search, spectral interpretation, and/or comparison with reference standards. Application of the workflow to analysis of unknown xenobiotics in plasma samples collected from four poisoned patients led to generation of xenobiotic profiles, which were regarded as xenobiotic fingerprints of the individual samples. Among 19 xenobiotics detected, 11 xenobiotics existed in a majority of the patients plasma samples, thus were considered as potential toxins. The follow-up database search led to the tentative identification of azithromycin (X5), alpha-chaconine (X9) and penfluridol (X12). The identity of X12 was further confirmed with its reference standard. In addition, one xenobiotic component (Y5) was tentatively identified as a penfluridol metabolite. The remaining unidentified xenobiotics listed in the xenobiotic fingerprints can be further characterized or identified in retrospective analyses after their spectral data and/or reference compounds are available. This HRMS-based workflow may have broad applications in the detection and identification of unknown xenobiotics in individual biological samples, such as forensic and toxicological analysis and sport enhancement drug screening. (C) 2016 Elsevier B.V. All rights reserved.
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| 12. |
- Cushing, Kevin, et al.
(författare)
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Reducing WBC background in cancer cell separation products by negative acoustic contrast particle immuno-acoustophoresis
- 2018
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 1000, s. 256-264
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells display acoustic properties enabling acoustophoretic separation from white blood cells (WBCs) with 2–3 log suppression of the WBC background. However, a subset of WBCs has overlapping acoustic properties with cancer cells, which is why label-free acoustophoretic cancer cell isolation needs additional purification prior to analysis. This paper reports for the first time a proof of concept for continuous flow acoustophoretic negative selection of WBCs from cancer cells using negative acoustic contrast elastomeric particles (EPs) activated with CD45-antibodies that specifically bind to WBCs. The EP/WBC complexes align at the acoustic pressure anti-nodes along the channel walls while unbound cancer cells focus to the pressure node in the channel center, enabling continuous flow based depletion of WBC background in a cancer cell product. The method does not provide a single process solution for the CTC separation challenge, but provides an elegant part to a multi-step process by further reducing the WBC background in cancer cell separation products derived from an initial step of label-free acoustophoresis. We report the recorded performance of the negative selection immuno-acoustophoretic WBC depletion and cancer cell recovery. To eliminate the negative impact of the separation due to the known problems of aggregation of negative acoustic contrast particles along the sidewalls of the acoustophoresis channel and to enable continuous separation of EP/WBC complexes from cancer cells, a new acoustic actuation method has been implemented where the ultrasound frequency is scanned (1.991MHz ± 100 kHz, scan rate 200 kHz ms−1). Using this frequency scanning strategy EP/WBC complexes were acoustophoretically separated from mixtures of WBCs spiked with breast and prostate cancer cells (DU145 and MCF-7). An 86-fold (MCF-7) and 52-fold (DU145) reduction of WBCs in the cancer cell fractions were recorded with separation efficiencies of 98.6% (MCF-7) and 99.7% (DU145) and cancer cell recoveries of 89.8% (MCF-7) and 85.0% (DU145).
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| 13. |
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| 14. |
- El-Beqqali, Aziza, 1966-, et al.
(författare)
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Molecularly imprinted polymer-sol-gel tablet toward micro-solid phase extraction : I. Determination of methadone in human plasma utilizing liquid chromatography-tandem mass spectrometry
- 2016
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 936, s. 116-122
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Tidskriftsartikel (refereegranskat)abstract
- In the present work molecularly imprinted sol-gel tablet (MIP-Tablet) was prepared. The MIP-sol-gel was prepared as a thin layer on polyethylene material in a tablet form. Methadone-d9 was selected as the template and 3-(propylmethacrylate)-trimethoxysilane was used as precursor. MIP-Tablet was applied for micro-solid phase extraction (μ-SPE). The MIP-Tablet was used for the determination of methadone in human plasma samples utilizing liquid chromatography-tandem mass spectrometry; and each tablet could be used twenty times. The extraction time was 10 min while desorption time was 6 min. Factors affecting the extraction efficiency such as desorption solvents, sample pH, salt addition, extraction time, desorption time and adsorption capacity were investigated. The calibration curves were obtained within the range of 5-5000 ng/mL using methadone in human plasma samples. The coefficients of determination (r(2)) values were >= 0.999 for all runs and the extraction recovery was >80%. The accuracy values for quality control samples varied from +3.6 to +9.7% and the inter-day precision (RSD %) values were ranged from 5.0 to 8.0%. The limit of detection was 1.0 ng/mL and the lower limit of quantification was 5 ng/mL utilizing methadone in human plasma samples.
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| 15. |
- Elmsjö, Albert, et al.
(författare)
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The co-feature ratio, a novel method for the measurement of chromatographic and signal selectivity in LC-MS-based metabolomics.
- 2017
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 956, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of analytical procedures, especially in regards to measuring chromatographic and signal selectivity, is highly challenging in untargeted metabolomics. The aim of this study was to suggest a new straightforward approach for a systematic examination of chromatographic and signal selectivity in LC-MS-based metabolomics. By calculating the ratio between each feature and its co-eluting features (the co-features), a measurement of the chromatographic selectivity (i.e. extent of co-elution) as well as the signal selectivity (e.g. amount of adduct formation) of each feature could be acquired, the co-feature ratio. This approach was used to examine possible differences in chromatographic and signal selectivity present in samples exposed to three different sample preparation procedures. The capability of the co-feature ratio was evaluated both in a classical targeted setting using isotope labelled standards as well as without standards in an untargeted setting. For the targeted analysis, several metabolites showed a skewed quantitative signal due to poor chromatographic selectivity and/or poor signal selectivity. Moreover, evaluation of the untargeted approach through multivariate analysis of the co-feature ratios demonstrated the possibility to screen for metabolites displaying poor chromatographic and/or signal selectivity characteristics. We conclude that the co-feature ratio can be a useful tool in the development and evaluation of analytical procedures in LC-MS-based metabolomics investigations. Increased selectivity through proper choice of analytical procedures may decrease the false positive and false negative discovery rate and thereby increase the validity of any metabolomic investigation.
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| 16. |
- Erturk, Gizem, et al.
(författare)
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Real-time prostate-specific antigen detection with prostate-specific antigen imprinted capacitive biosensors
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 891, s. 120-129
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Tidskriftsartikel (refereegranskat)abstract
- Prostate specific antigen (PSA) is a valuable biomarker for early detection of prostate cancer, the third most common cancer in men. Ultrasensitive detection of PSA is crucial to screen the prostate cancer in an early stage and to detect the recurrence of the disease after treatment. In this report, microcontact-PSA imprinted (PSA-MIP) capacitive biosensor chip was developed for real-time, highly sensitive and selective detection of PSA. PSA-MIP electrodes were prepared in the presence of methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker via UV polymerization. Immobilized Anti-PSA antibodies on electrodes (Anti-PSA) for capacitance measurements were also prepared to compare the detection performances of both methods. The electrodes were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV) and real-time PSA detection was performed with standard PSA solutions in the concentration range of 10 fg mL(-1) -100 ng mL(-1). The detection limits were found as 8.0 x 10(-5) ng mL(-1) (16 x 10(-17) M) and 6.0 x 10(-4) ng mL(-1) (12 x 10(-16) M) for PSA-MIP and Anti-PSA electrodes, respectively. Selectivity studies were performed against HSA and IgG and selectivity coefficients were calculated. PSA detection was also carried out from diluted human serum samples and finally, reproducibility of the electrodes was tested. The results are promising and show that when the sensitivity of the capacitive system is combined with the selectivity and reproducibility of the microcontact-imprinting procedure, the resulting system might be used successfully for real-time detection of various analytes even in very low concentrations. (C) 2015 Elsevier B.V. All rights reserved.
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| 17. |
- Eskandari, Mahboubeh, et al.
(författare)
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Polyphenol-hydrogen peroxide reactions in skin : In vitro model relevant to study ROS reactions at inflammation
- 2019
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1075, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- Antioxidants are important to protect and maintain biological barriers, such as the skin. Antioxidant effects are often assessed using clinical trials, however these tests are costly and time consuming. In this work we introduce a skin membrane-covered oxygen electrode (SCOE) as an in vitro tool for monitoring H2O2 and antioxidant reactions in skin. The SCOE gives amperometric response to H2O2 concentrations down to 0.05 mM. More importantly, the electrode allows measurements of polyphenol penetration and reaction with H2O2 in skin. Measurements with SCOE show that lipophilic polyphenols such as quercetin, piceatannol, resveratrol, and plant extract from Plantago major impose their antioxidant effect in skin within 2-20 min. Rutin is however too hydrophilic to penetrate into stratum corneum and therefore cannot deliver its antioxidant effect during similar time interval. The measurements are interpreted considering polyphenol partition-penetration through stratum corneum and the reaction with the H2O2-catalase system in the skin. The contribution of other enzymes will be addressed in the future. (C) 2019 Elsevier B.V. All rights reserved.
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| 18. |
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| 19. |
- Gouveia-Figueira, Sandra C., et al.
(författare)
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Mass spectrometry profiling reveals altered plasma levels of monohydroxy fatty acids and related lipids in healthy humans after controlled exposure to biodiesel exhaust
- 2018
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1018, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- Experimental human exposure studies are an effective tool to study adverse health effects from acute inhalation of particulate matter and other constituents of air pollution. In this randomized and double-blinded crossover study, we investigated the systemic effect on bioactive lipid metabolite levels after controlled biodiesel exhaust exposure of healthy humans and compared it to filtered air at a separate exposure occasion. Eicosanoids and other oxylipins, as well as endocannabinoids and related lipids, were quantified in plasma from 14 healthy volunteers at baseline and at three subsequent time points (2, 6, and 24 h) after 1 h exposure sessions. Protocols based on liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS) methods were developed to detect temporal changes in circulating levels after biodiesel exhaust exposure. The exhaust was generated by a diesel engine fed with an undiluted rapeseed methyl ester fuel. Among the 51 analyzed lipid metabolites, PGF(2 alpha), 9,10-DiHOME, 9-HODE, 5-HETE, 11-HETE, 12-HETE, and DEA displayed significant responsiveness to the biodiesel exhaust exposure as opposed to filtered air. Of these, 9-HODE and 5-HETE at 24 h survived the 10% false discovery rate cutoff (p < 0.003). Hence, the majority of the responsive lipid metabolites were monohydroxy fatty acids. We conclude that it is possible to detect alterations in circulating bioactive lipid metabolites in response to biodiesel exhaust exposure using LC-MS/MS, with emphasis on metabolites with inflammation related properties and implications on cardiovascular health and disease. These observations aid future investigations on air pollution effects, especially with regard to cardiovascular outcomes.
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| 20. |
- Hakonen, Aron, 1970, et al.
(författare)
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Explosive and chemical threat detection by surface-enhanced Raman scattering: A review
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 893, s. 1-13
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Forskningsöversikt (refereegranskat)abstract
- Acts of terror and warfare threats are challenging tasks for defense agencies around the world and of growing importance to security conscious policy makers and the general public. Explosives and chemical warfare agents are two of the major concerns in this context, as illustrated by the recent Boston Marathon bombing and nerve gas attacks on civilians in the Middle East. To prevent such tragic disasters, security personnel must be able to find, identify and deactivate the threats at multiple locations and levels. This involves major technical and practical challenges, such as detection of ultra-low quantities of hazardous compounds at remote locations for anti-terror purposes and monitoring of environmental sanitation of dumped or left behind toxic substances and explosives. Surface-enhanced Raman scattering (SERS) is one of todays most interesting and rapidly developing methods for label-free ultrasensitive vibrational "fingerprinting" of a variety of molecular compounds. Performance highlights include atto-molar detection of TNT and DNT explosives, a sensitivity that few, if any, other technique can compete with. Moreover, instrumentation needed for SERS analysis are becoming progressively better, smaller and cheaper, and can today be acquired for a retail price close to 10,000 US$. This contribution aims to give a comprehensive overview of SERS as a technique for detection of explosives and chemical threats. We discuss the prospects of SERS becoming a major tool for convenient in-situ threat identification and we summarize existing SERS detection methods and substrates with particular focus on ultra-sensitive real-time detection. General concepts, detection capabilities and perspectives are discussed in order to guide potential users of the technique for homeland security and anti-warfare purposes. (C) 2015 Elsevier B.V. All rights reserved.
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| 21. |
- Horvath, Daniel G., et al.
(författare)
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Sorting by interfacial tension (SIFT) : Label-free enzyme sorting using droplet microfluidics
- 2019
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Ingår i: Analytica Chimica Acta. - : ELSEVIER. - 0003-2670 .- 1873-4324. ; 1089, s. 108-114
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Tidskriftsartikel (refereegranskat)abstract
- Droplet microfluidics has the ability to greatly increase the throughput of screening and sorting of enzymes by carrying reagents in picoliter droplets flowing in inert oils. It was found with the use of a specific surfactant, the interfacial tension of droplets can be very sensitive to droplet pH. This enables the sorting of droplets of different pH when confined droplets encounter a microfabricated trench. The device can be extended to sort enzymes, as a large number of enzymatic reactions lead to the production of an acidic or basic product and a concurrent change in solution pH. The progress of an enzymatic reaction is tracked from the position of a flowing train of droplets. We demonstrate the sorting of esterase isoenzymes based on their enzymatic activity. This label-free technology, that we dub droplet sorting by interfacial tension (SIFT), requires no active components and would have applications for enzyme sorting in high-throughput applications that include enzyme screening and directed evolution of enzymes.
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| 22. |
- Hu, Jiwen, et al.
(författare)
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A logic gate-based fluorogenic probe for Hg2+ detection and its applications in cellular imaging
- 2016
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Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 919, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- A new colorimetric and fluorogenic probe (RN3) based on rhodamine-B has been successfully designed and synthesized. It displays a selective response to Hg2+ in the aqueous buffer solution over the other competing metals. Upon addition of Hg2+, the solution of RN3 exhibits a naked eye observable color change from colorless to red and an intensive fluorescence with about 105-fold enhancement. The changes in the color and fluorescence are ascribed to the ring-opening of spirolactam in rhodamine fluorophore, which is induced by a binding of the constructed receptor to Hg2+ with the association and dissociation constants of 0.22 x 10(5) M-1 and 25.2 mM, respectively. The Jobs plot experiment determines a 1: 1 binding stoichiometry between RN3 and Hg2+. The resultant "turn-on" fluorescence in buffer solution, allows the application of a method to determine Hg2+ levels in the range of 4.0-15.0 mu M, with the limit of detection (LOD) calculated at 60.7 nM (3 sigma/slope). In addition, the fluorescence turn-off and color fading-out happen to the mixture of RN3-Hg2+ by further addition of I- or S2-. The reversible switching cycles of fluorescence intensity upon alternate additions of Hg2+ and S2- demonstrate that RN3 can perform as an INHIBIT logic gate. Furthermore, the potential of RN3 as a fluorescent probe has been demonstrated for cellular imaging. (C) 2016 Elsevier B.V. All rights reserved.
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| 23. |
- Hu, Zhang-Jun, et al.
(författare)
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A TPA-caged precursor of (imino)coumarin for "turn-on" fluorogenic detection of Cu
- 2016
-
Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 933, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- We strategize to utilize the precursors of (imino) coumarin fluorophores to deliver novel reactive Cu+ probes, where tris[(2-pyridyl)-methyl] amine (TPA) works as a reactive receptor towards Cu+. To verify this strategy, CP1, a representative probe and relevant sensing behaviors towards Cu+ are presented here. CP1 features good solubility and fast response for monitoring labile copper in aqueous solution and live cells. The sensing mechanism of CP1 is determined by HPLC titration and mass spectrometric analysis. The probe CP1 exhibits a 60-fold fluorescence enhancement and a detection limitation of 10.8 nM upon the detection of Cu+. CP1 is further applied for imaging labile copper in live cells. This work provides a starting point for future development of Cu+ probes, based on in situ formation of (imino) coumarin scaffolds, as well as their further investigations of copper signaling and biological events. (C) 2016 Elsevier B.V. All rights reserved.
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| 24. |
- Huang, Hui, et al.
(författare)
-
Synthesis of a novel electrode material containing phytic acid-polyaniline nanofibers for simultaneous determination of cadmium and lead ions
- 2016
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 947, s. 32-41
-
Tidskriftsartikel (refereegranskat)abstract
- The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd2+ and Pb2+ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd2+ in a range of 0.05–60 μg L−1, with the detection limit (S/N = 3) of 0.02 μg L−1, and for Pb2+ in a range of 0.1–60 μg L−1, with the detection limit (S/N = 3) of 0.05 μg L−1. The new electrode was successfully applied to real water samples for simultaneous detection of Cd2+ and Pb2+ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions.
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| 25. |
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| 26. |
- Karimpour, Masoumeh, et al.
(författare)
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Postprandial metabolomics : A pilot mass spectrometry and NMR study of the human plasma metabolome in response to a challenge meal
- 2016
-
Ingår i: Analytica Chimica Acta. - Elsevier : Elsevier BV. - 0003-2670 .- 1873-4324. ; 908, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- The study of postprandial metabolism is relevant for understanding metabolic diseases and characterizing personal responses to diet. We combined three analytical platforms – gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) – to validate a multi-platform approach for characterizing individual variation in the postprandial state. We analyzed the postprandial plasma metabolome by introducing, at three occasions, meal challenges on a usual diet, and 1.5 years later, on a modified background diet. The postprandial response was stable over time and largely independent of the background diet as revealed by all three analytical platforms. Coverage of the metabolome between NMR and GC-MS included more polar metabolites detectable only by NMR and more hydrophobic compounds detected by GC-MS. The variability across three separate testing occasions among the identified metabolites was in the range of 1.1–86% for GC-MS and 0.9–42% for NMR in the fasting state at baseline. For the LC-MS analysis, the coefficients of variation of the detected compounds in the fasting state at baseline were in the range of 2–97% for the positive and 4–69% for the negative mode. Multivariate analysis (MVA) of metabolites detected with GC-MS revealed that for both background diets, levels of postprandial amino acids and sugars increased whereas those of fatty acids decreased at 0.5 h after the meal was consumed, reflecting the expected response to the challenge meal. MVA of NMR data revealed increasing postprandial levels of amino acids and other organic acids together with decreasing levels of acetoacetate and 3-hydroxybutanoic acid, also independent of the background diet. Together these data show that the postprandial response to the same challenge meal was stable even though it was tested 1.5 years apart, and that it was largely independent of background diet. This work demonstrates the efficacy of a multi-platform metabolomics approach followed by multivariate and univariate data analysis for a broad-scale screen of the individual metabolome, particularly for studies using repeated measures to determine dietary response phenotype.
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| 27. |
- Liem-Nguyen, Van, 1986-, et al.
(författare)
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Determination of picomolar concentrations of thiol compounds in natural waters and biological samples by tandem mass spectrometry with online preconcentration and isotope-labeling derivatization
- 2019
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1067, s. 71-78
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Tidskriftsartikel (refereegranskat)abstract
- We present a sensitive, selective and robust method for the determination of 14 thiol compounds in aqueous samples. Thiols were derivatized with omega-bromoacetonylquinolinium bromide (BQB) and its deuterium labeled equivalent D7-omega-bromoacetonylquinolinium bromide (D7). Derivatized thiols were preconcentrated by online solid-phase extraction (SPE) followed by liquid chromatography separation and electrospray ionization tandem mass spectrometry determination (SPE/LC-ESI-MS/MS). The robustness of the method was validated for wide ranges in pH, salinity, and concentrations of sulfide and dissolved organic carbon (DOC) to cover contrasting natural water types. The limits of detection (LODs) for the thiols were 3.1-66 pM. Between 6 and 14 of the thiols were detected in different natural sample types at variable concentrations: boreal wetland porewater (0.7-51 nM), estuarine sediment porewater (50 pM-11 nM), coastal sea water (60 pM-16 nM), and sulfate reducing bacterium cultures (80 pM-4 nM). MS/MS fragmentation of the compounds produces two pairs of common product ions, m/z 130.2/137.1 and 218.1/225.1, which enables scanning for unknown thiols in precursor ion scan mode. Using this approach, we identified cysteine, mercaptoacetic acid, N-acetyl-L-cysteine and sulfurothioic S-acid in boreal wetland porewater. The performance of the developed method sets a new state of the art for the determination of thiol compounds in environmental and biological samples.
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| 28. |
- Lisak, Grzegorz, et al.
(författare)
-
Textile-based sampling for potentiometric determination of ions
- 2015
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 877, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- Potentiometric sensing utilizing textile-based micro-volume sampling was applied and evaluated for the determination of clinically (Na+, K+, Cl-) and environmentally (Cd2+, Pb2+ and pH) relevant analytes. In this technological design, calibration solutions and samples were absorbed into textiles while the potentiometric cells (ion-selective electrodes and reference electrode) were pressed against the textile. Once the liquid, by wicking action, reached the place where the potentiometric cell was pressed onto the textile, hence closing the electric circuit, the potentiometric response was obtained. Cotton, polyamide, polyester and their blends with elastane were applied for micro-volume sampling. The textiles were found to influence the determination of pH in environmental samples with pH close to neutral and Pb2+ at low analyte concentrations. On the other hand, textile-based micro-volume sampling was successfully applied in measurements of Na+ using solid-contact sodium-selective electrodes utilizing all the investigated textiles for sampling. It was found that in order to extend the application of textile-based sampling toward environmental analysis of ions it will be necessary to tailor the physio-chemical properties of the textile materials. In general, textile-based sampling opens new possibilities for direct chemical analysis of small-volume samples and provide a simple and low-cost method to screen various textiles for their effects on samples to identify which textiles are the most suitable for on-body sensing. (C) 2015 Elsevier B.V. All rights reserved.
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| 29. |
- Lluch, E., et al.
(författare)
-
Analysis of 210Pb in water samples with plastic scintillation resins
- 2016
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 940, s. 38-45
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Tidskriftsartikel (refereegranskat)abstract
- 210Pb is a radioactive lead isotope present in the environment as member of the 238U decay chain. Since it is a relatively long-lived radionuclide (T1/2 = 22.2 years), its analysis is of interest in radiation protection and the geochronology of sediments and artwork. Here, we present a method for analysing 210Pb using plastic scintillation resins (PSresins) packaged in solid-phase extraction columns (SPE cartridge). The advantages of this method are its selectivity, the low limit of detection, as well as reductions in the amount of time and reagents required for analysis and the quantity of waste generated. The PSresins used in this study were composed of a selective extractant (4′,4″(5″)-Di-tert-butyldicyclohexano-18-crown-6 in 1-octanol) covering the surface of plastic scintillation microspheres. Once the amount of extractant (1:1/4) and medium of separation (2 M HNO3) were optimised, PSresins in SPE cartridges were calibrated with a standard solution of 210Pb. 210Pb could be fully separated from its daughters, 210Bi and 210Po, with a recovery value of 91(3)% and detection efficiency of 44(3)%. Three spiked water samples (one underground and two river water samples) were analysed in triplicates with deviations lower than 10%, demonstrating the validity of the PS resin method for 210Pb analysis.
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| 30. |
- Machado, Isabel, et al.
(författare)
-
Rapid and specific detection of Salmonella infections using chemically modified nucleic acid probes
- 2019
-
Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 1054, s. 157-166
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Tidskriftsartikel (refereegranskat)abstract
- Salmonella is a leading source of bacterial foodborne illness in humans, causing gastroenteritis outbreaks with bacteraemia occurrences that can lead to clinical complications and death. Eggs, poultry and pig products are considered as the main carriers of the pathogenic Salmonella for humans. To prevent this relevant zoonosis, key changes in food safety regulations were undertaken to improve controls in the food production chain. Despite these measures, large outbreaks of salmonellosis were reported worldwide in the last decade. Thus, new strategies for Salmonella detection are a priority for both, food safety and public health authorities. Such detection systems should provide significant reduction in diagnostic time (hours) compared to the currently available methods (days). Herein, we report on the discovery and characterization of nucleic acid probes for the sensitive and specific detection of live Salmonella within less than 8 h of incubation. We are the first to postulate the nuclease activity derived from Salmonella as biomarker of infection and its utility to develop innovative detection strategies. Our results have shown the screening and identification of two oligonucleotide sequences (substrates) as the most promising probes for detecting Salmonella - Sal-3 and Sal-5. The detection limits for both probes were determined with the reference Salmonella Typhimurium (STM 1) and Salmonella Enteritidis (SE 1) cultures. Sal-3 has reported LOD values around 10(5) CFU mL(-1) for STM 1 and 10(4) CFU mL(-1) for SE 1, while Sal-5 proves to be a slightly better probe, with LODs of 10(4) CFU mL(-1) for STM 1 and 10(4) CFU mL(-1) for SE 1. Both selected probes have shown the capability to recognize 49 out of 51 different Salmonella serotypes tested in vitro and the most frequent serotypes in porcine mesenteric lymph nodes as a standard sample used in fattening-pig salmonellosis baseline studies. Notably, our results showed 100% correlation between nuclease detection and the PCR-InvA or ISO-6579 standard method, underlining the great potential of this innovative nucleic acids technology to be implemented as a rapid method for food safety testing. (C) 2018 Elsevier B.V. All rights reserved.
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| 31. |
- Miles, J., et al.
(författare)
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A new technique for probing chirality via photoelectron circular dichroism
- 2017
-
Ingår i: Analytica Chimica Acta. - Amsterdam : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 984, s. 134-139
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Tidskriftsartikel (refereegranskat)abstract
- We present a proof-of-principle approach for discriminating chiral enantiomers based on the phenomenon of multiphoton photoelectron circular dichroism. A novel stereo detection setup was used to measure the number of photoelectrons emitted from chiral molecules in directions parallel or antiparallel to the propagation of the ionising femtosecond laser pulses. In this study, we show how these asymmetries in the ketones camphor and fenchone depend upon the ellipticity of the laser pulses and the enantiomeric excess of the sample. By using a high repetition rate femtosecond laser, enantiomer excesses with uncertainties at the few-percent level could be measured in close to real-time. As the instrument is compact, and commercial turnkey femtosecond lasers are readily available, the development of a stand-alone chiral analysis instrument for a range of applications is now possible.
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| 32. |
- Pankratova, Galina, et al.
(författare)
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Extracellular electron transfer features of Gram-positive bacteria
- 2019
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 1076, s. 32-47
-
Tidskriftsartikel (refereegranskat)abstract
- Electroactive microorganisms possess the unique ability to transfer electrons to or from solid phase electron conductors, e.g., electrodes or minerals, through various physiological mechanisms. The processes are commonly known as extracellular electron transfer and broadly harnessed in microbial electrochemical systems, such as microbial biosensors, microbial electrosynthesis, or microbial fuel cells. Apart from a few model microorganisms, the nature of the microbe-electrode conductive interaction is poorly understood for most of the electroactive species. The interaction determines the efficiency and a potential scaling up of bioelectrochemical systems. Gram-positive bacteria generally have a thick electron non-conductive cell wall and are believed to exhibit weak extracellular electron shuttling activity. This review highlights reported research accomplishments on electroactive Gram-positive bacteria. The use of electron-conducting polymers as mediators is considered as one promising strategy to enhance the electron transfer efficiency up to application scale. In view of the recent progress in understanding the molecular aspects of the extracellular electron transfer mechanisms of Enterococcus faecalis, the electron transfer properties of this bacterium are especially focused on. Fundamental knowledge on the nature of microbial extracellular electron transfer and its possibilities can provide insight in interspecies electron transfer and biogeochemical cycling of elements in nature. Additionally, a comprehensive understanding of cell-electrode interactions may help in overcoming insufficient electron transfer and restricted operational performance of various bioelectrochemical systems and facilitate their practical applications.
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| 33. |
- Pavankumar, A. R., et al.
(författare)
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Bioanalytical advantages of a novel recombinant apyrase enzyme in ATP-based bioluminescence methods
- 2018
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1025, s. 118-123
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasensitive measurements of intracellular ATP (intATP) based on the firefly luciferase reactions are frequently used to enumerate bacterial or mammalian cells. During clinical applications, extracellular ATP (extATP) should be depleted in biological samples since it interferes with intATP and affects the quantification of bacteria. The extATP can be eliminated by ATP-degrading enzymes but complete hydrolysis of extATP remains a challenge for today's commercial enzymes. The catalytic efficiency of ATP-degrading enzymes depends on enzyme characteristics, sample composition and the ability to deplete diphosphates, triphosphates and their complexes generated during the reaction. This phenomenon restricts the usage of bioluminescence-based ATP methods in clinical diagnostics. In light of this, we have developed a recombinant Shigella flexneri apyrase (RSFA) enzyme and analysed its ATP depletion potential with five commercial biochemical sources including potato apyrase, acid phosphatase, alkaline phosphatase, hexokinase and glycerol kinase. The RSFA revealed superior activity by completely eliminating the extracellular ATP and ATP-complexes, even in biological samples like urine and serum. Therefore, our results can potentially unwrap the chemical and bio-analytical applications of ATP-based bioluminescence tests to develop highly sensitive point-of-care diagnostics.
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| 34. |
- Petersson, Klara, et al.
(författare)
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Acoustofluidic hematocrit determination
- 2018
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 1000, s. 199-204
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Tidskriftsartikel (refereegranskat)abstract
- Hematocrit (HCT) measurements of blood from patients, blood donors and athletes are routinely performed on a daily basis. These measurements are often performed in centralized hospital labs by whole blood analyzers, which leads to long time-to-result. On site measurements, based on centrifugation can be done, but these assays require manual handling, are slow and can just measure HCT in contrast to the central lab whole blood analyzers. In this work, we present a microfluidic based method to measure HCT in blood samples by acoustic separation of whole blood into discrete regions of plasma and red blood cells. Comparison of the areas of the red blood cell and plasma regions gives an accurate HCT value, with a linear correlation to the centrifugation-based reference method. A readout can be performed within 2 s of acoustic actuation providing a readout accuracy of approximately 3% points (pp) HCT. Additional accuracy can be achieved by extending the acoustic actuation to 20 s, yielding an error of less than 1 pp HCT. This acoustic tool is optimal for integration into a lab-on-a-chip device with in-line measurements of different clinical parameters.
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| 35. |
- Phal, Sereilakhena, et al.
(författare)
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Determination of methotrexate in spiked human blood serum using multi-frequency electrochemical immittance spectroscopy and multivariate data analysis
- 2017
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 987, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55. The data were analysed using multivariate data analysis and showed a concentration dependence and time dependence that could be separated. This allowed the calculation of a multivariate calibration model. The model showed good linear behavior on a logarithmic scale offering a detection limit of 5 × 10−12 mol L−1.
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| 36. |
- Riboni, Nicolò, 1989-, et al.
(författare)
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Conformationally blocked quinoxaline cavitand as solid-phase microextraction coating for the selective detection of BTEX in air
- 2016
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 905, s. 79-84
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Tidskriftsartikel (refereegranskat)abstract
- A tetraquinoxaline cavitand functionalized with methylenoxy bridges at the upper rim is proposed as selective solid-phase microextraction (SPME) coating for the determination of BTEX at trace levels in air. The SPME fibers were characterized in terms of film thickness, morphology, thermal stability and extraction capabilities. An average coating thickness of 35 (±4) μm, a thermal stability up to 350 °C and a good fiber-to-fiber and batch-to-batch repeatability with RSD lower than 15% were obtained. Excellent enrichment factors ranging from 360–700 × 103 were obtained for the investigated compounds. Finally, method validation proved the capabilities of the developed coating for the selective sampling of BTEX, achieving LOD values in the 0.4–1.2 ng m−3 range.
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| 37. |
- Riboni, Nicolò, 1989-, et al.
(författare)
-
Sol-gel coated ion sources for liquid chromatography-direct electronionization mass spectrometry
- 2017
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 978, s. 35-41
-
Tidskriftsartikel (refereegranskat)abstract
- Advances in interfacing liquid chromatography and electron ionization mass spectrometry are presented. New ion source coatings synthesized by sol-gel technology were developed and tested as vaporization surfaces in terms of peak intensity, peak width and peak delay for the liquid chromatography-direct electron ionization mass spectrometry (Direct-EI) determination of environmental pollutants like polycyclic aromatic hydrocarbons and steroids. Silica-, titania-, and zirconia-based coatings were sprayed inside the stainless steel ion source and characterized in terms of thermal stability, film thickness and morphology. Negligible weight losses until 350–400 °C were observed for all the materials, with coating thicknesses in the 6 (±1)-11 (±2) μm range for optimal ionization process. The best performances in terms of both peak intensity and peak width were obtained by using the silica-based coating: the detection of the investigated compounds was feasible at low ng μl−1 levels with a good precision (RSD < 9% for polycyclic aromatic hydrocarbons and <11% for hormones).
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| 38. |
- Sekretaryova, Alina, et al.
(författare)
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Total phenol analysis of weakly supported water using a laccase-based microband biosensor.
- 2016
-
Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 907, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M−1 cm−2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.
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| 39. |
- Souihi, Nabil, et al.
(författare)
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OPLS in batch monitoring - Opens up new opportunities
- 2015
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 857, s. 28-38
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Tidskriftsartikel (refereegranskat)abstract
- In batch statistical process control (BSPC), data from a number of "good" batches are used to model the evolution (trajectory) of the process and they also define model control limits, against which new batches may be compared. The benchmark methods used in BSPC include partial least squares (PLS) and principal component analysis (PCA). In this paper, we have used orthogonal projections to latent structures (OPLS) in BSPC and compared the results with PLS and PCA. The experimental study used was a batch hydrogenation reaction of nitrobenzene to aniline characterized by both UV spectroscopy and process data. The key idea is that OPLS is able to separate the variation in data that is correlated to the process evolution (also known as 'batch maturity index') from the variation that is uncorrelated to process evolution. This separation of different types of variations can generate different batch trajectories and hence lead to different established model control limits to detect process deviations. The results demonstrate that OPLS was able to detect all process deviations and provided a good process understanding of the root causes for these deviations. PCA and PLS on the other handwere shown to provide different interpretations for several of these process deviations, or in some cases they were unable to detect actual process deviations. Hence, the use of OPLS in BSPC can lead to better fault detection and root cause analysis as compared to existing benchmark methods and may therefore be used to complement the existing toolbox.
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| 40. |
- Svan, Alfred, 1986-, et al.
(författare)
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The differences in matrix effect between supercritical fluid chromatography and reversed phase liquid chromatography coupled to ESI/MS
- 2018
-
Ingår i: Analytica Chimica Acta. - : ELSEVIER SCIENCE BV. - 0003-2670 .- 1873-4324. ; 1000, s. 163-171
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Tidskriftsartikel (refereegranskat)abstract
- For many sample matrices, matrix effects are a troublesome phenomenon using the electrospray ionization source. The increasing use of supercritical fluid chromatography with CO2 in combination with the electrospray ionization source for MS detection is therefore raising questions: is the matrix effect behaving differently using SFC in comparison with reversed phase LC? This was investigated using urine, plasma, influent-and effluent-wastewater as sample matrices. The matrix effect was evaluated using the post-extraction addition method and through post-column infusions. Matrix effect profiles generated from the post-column infusions in combination with time of flight-MS detection provided the most valuable information for the study. The combination of both qualitative and semi-quantitative information with the ability to use HRMS-data for identifying interfering compounds from the same experiment was very useful, and has to the authors' knowledge not been used this way before. The results showed that both LC and SFC are affected by matrix effects, however differently depending on sample matrix. Generally, both suppressions and enhancements were seen, with a higher amount of enhancements for LC, where 65% of all compounds and all sample matrices were enhanced, compared to only 7% for SFC. Several interferences were tentatively identified, with phospholipids, creatinine, and metal ion clusters as examples of important interferences, with different impact depending on chromatographic technique. SFC needs a different strategy for limiting matrix interferences, owing to its almost reverse retention order compared to RPLC.
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| 41. |
- Tenje, Maria, et al.
(författare)
-
Acoustic trapping as a generic non-contact incubation site for multiplex bead-based assays.
- 2015
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 853, s. 682-688
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we show a significantly reduced assay time and a greatly increased bead recovery for a commercial Luminex-based multiplex diagnostic immunoassay by performing all liquid handling steps of the assay protocol in a non-contact acoustic trapping platform. The Luminex assay is designed for detecting antibodies in poultry serum for infectious bursal disease virus, infectious bronchitis virus, Newcastle disease virus and avian reovirus. Here, we show proof-of-concept of a microfluidic system capable of being fully automated and handling samples in a parallel format with a miniature physical footprint where the affinity beads are retained in a non-contact levitated mode in a glass capillary throughout the assay protocol. The different steps are: incubation with the serum sample, secondary antibodies and fluorescent reporters and finally washing to remove any non-specifically bound species. A Luminex 200 instrument was used for the readout. The flow rates applied to the capillary during the initial trapping event and the wash steps were optimised for maximum bead recovery, resulting in a bead recovery of 75% for the complete assay. This can be compared to a bead recovery of approximately 30% when an automatic wash station was used when the assay was performed in the conventional manual format. The time for the incubation steps for a single assay was reduced by more than 50%, without affecting assay performance, since intermediate wash steps became redundant in the continuously perfused bead trapping capillary. We analyzed seven samples, in triplicates, and we can show that the readout of the assay performed in the acoustic trap compared 100% to the control ELISAs (positive or negative readout) and resulted in comparable S/P values as the conventional manual protocol. As the acoustic trapping does not require the particles to have magnetic properties, a greater degree of freedom in selecting microparticles can be provided. In extension, this can provide an opportunity to develop cheaper and more effective microparticles.
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| 42. |
- Tesfalidet, Solomon, et al.
(författare)
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Detection of methotrexate in a flow system using electrochemical impedance spectroscopy and multivariate data analysis
- 2016
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 914, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Methotrexate (MTX), a common pharmaceutical drug in cancer therapy and treatment of rheumatic diseases, is known to cause severe adverse side effects at high dose. As the side effect may be life threatening, there is an urgent need for a continuous, bed-side monitoring of the nominal MTX serum level in a patient while the chemical is being administered. This article describes a detection of MTX using a flow system that consists two modified gold electrodes. Interaction of MTX with the antibodies fixed on the electrode surface is detected by electrochemical impedance spectroscopy and evaluated using singular value decomposition (SVD). The key finding of this work is that the change in the electrode capacitance is found to be quantitative with respect to the concentration of MTX. Moreover a calibration curve constructed using the principal component regression method has a linear range of six orders of magnitude and a detection limit of 1.65 × 10−10 M.
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| 43. |
- Tolu, Julie, et al.
(författare)
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High-throughput characterization of sediment organic matter by pyrolysis-gas chromatography/mass spectrometry and multivariate curve resolution : A promising analytical tool in (paleo) limnology
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 880, s. 93-102
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Tidskriftsartikel (refereegranskat)abstract
- Molecular-level chemical information about organic matter (OM) in sediments helps to establish the sources of OM and the prevalent degradation/diagenetic processes, both essential for understanding the cycling of carbon (C) and of the elements associated with OM (toxic trace metals and nutrients) in lake ecosystems. Ideally, analytical methods for characterizing OM should allow high sample throughput, consume small amounts of sample and yield relevant chemical information, which are essential for multidisciplinary, high-temporal resolution and/or large spatial scale investigations. We have developed a high-throughput analytical method based on pyrolysis-gas chromatography/mass spectrometry and automated data processing to characterize sedimentary OM in sediments. Our method consumes 200 mg of freeze-dried and ground sediment sample. Pyrolysis was performed at 450 degrees C, which was found to avoid degradation of specific biomarkers (e. g., lignin compounds, fresh carbohydrates/cellulose) compared to 650 degrees C, which is in the range of temperatures commonly applied for environmental samples. The optimization was conducted using the top ten sediment samples of an annually resolved sediment record (containing 16-18% and 1.3-1.9% of total carbon and nitrogen, respectively). Several hundred pyrolytic compound peaks were detected of which over 200 were identified, which represent different classes of organic compounds (i. e., n-alkanes, n-alkenes, 2-ketones, carboxylic acids, carbohydrates, proteins, other N compounds, (methoxy) phenols, (poly) aromatics, chlorophyll and steroids/hopanoids). Technical reproducibility measured as relative standard deviation of the identified peaks in triplicate analyses was 5.5 +/- 4.3%, with 90% of the RSD values within 10% and 98% within 15%. Finally, a multivariate calibration model was calculated between the pyrolytic degradation compounds and the sediment depth (i. e., sediment age), which is a function of degradation processes and changes in OM source type. This allowed validation of the Py-GC/MS dataset against fundamental processes involved in OM cycling in aquatic ecosystems.
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| 44. |
- Trinh, Minh Ngoc, 1978-, et al.
(författare)
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Self-heated Ag-decorated SnO2 nanowires with low power consumption used as a predictive virtual multisensor for H2S-selective sensing
- 2019
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1069, s. 108-116
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Tidskriftsartikel (refereegranskat)abstract
- Multisensor systems with low-power consumption are emerging for the Internet of Things. In this work, we demonstrate the use of self-heated networked Ag-decorated SnO2 NW sensors integrated into a portable module for selective detection of H2S gas at low power consumption, and the integrated system is simulated as a virtual multisensor under varying heating powers for identifying and quantifying different reducing gases. The H2S gas-sensing characterisations at the different self-heating powers of 2–10 mW showed that the gas response significantly increased with the increase in Ag density decoration and the heated power strongly affected the gas-sensing performance and sensor stability. Excellent response of 21.2 to 0.5 ppm H2S gas was obtained at a low heating power of 2 mW with an acceptable response/recovery time of 18/980 s. The increase of the heating power over 20 mW can destroy the devices. The integrated system could selectively detect H2S at the heating power below 4 mW and H2, C2H5OH and NH3gases at the heating power upon 4 mW. The virtual multisensor could discriminate qualitatively (with an accuracy of 100%) and quantitatively H2S, H2, NH3, C2H5OH (Ethanol) and CH3COCH3 (Aceton) gases with average errors of 13.5%, 14.7%, 16.8%, 16.9%, and 14.8%, respectively. The proposed sensing platform is a promising candidate for selective detection of H2S gas and virtual multisensor with low power consumption for mobile or wireless network devices.
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| 45. |
- Yuan, Bo, et al.
(författare)
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Methods for trace analysis of short-, medium-, and long-chain chlorinated paraffins : Critical review and recommendations
- 2019
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1074, s. 16-32
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Forskningsöversikt (refereegranskat)abstract
- Many methods for quantifying chlorinated paraffins (CPs) yield only a total concentration of the mixture as a single value. With appropriate analytical instrumentation and quantification methods, more reliable and detailed analysis can be performed by quantifying total concentrations of short-, medium-, and longchain CPs (SCCPs, MCCPs, and LCCPs), and in the current optimal situation by quantifying individual carbon-chlorine congener groups (CnClm). Sample extraction and clean-up methods for other persistent organochlorines that have been adapted for recovery of CPs must be applied prior to quantification with appropriate quality assurance and quality control to ensure applicability of the methods for SCCPs, MCCPs, and LCCPs. Part critical review, part tutorial, and part perspective, this paper provides practical guidance to analytical chemists who are interested in establishing a method for analysis of CPs in their lab facilities using commercial reference standards, or for expanding existing analysis of total CPs or SCCPs to analysis of SCCPs, MCCPs, and LCCPs, or to analysis of CnClm congener groups.
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