| 1. |
- Abujrais, Sandy, et al.
(författare)
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Analysis of tryptophan metabolites and related compounds in human and murine tissue : development and validation of a quantitative and semi-quantitative method using high resolution mass spectrometry
- 2024
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Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 16:7, s. 1074-1082
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the metabolic differences between human and murine plasma in addition to differences between murine subcutaneous and visceral white adipose tissue. A quantitative and semi-quantitative targeted method was developed and validated for this purpose. The quantitative method includes tryptophan and its metabolites in addition to tyrosine, phenylalanine, taurine, B vitamins, neopterin, cystathionine and hypoxanthine. While the semi-quantitative method includes; 3-indoleacetic acid, 5-hydroxyindoleacetic acid, acetylcholine, asymmetric dimethylarginine, citrulline and methionine. Sample preparation was based on protein precipitation, while quantification was conducted using ultrahigh-performance liquid chromatography coupled to a quadrupole Orbitrap tandem mass spectrometer with electrospray ionization in the parallel reaction monitoring (PRM) mode. The low limit of quantification for all metabolites ranged from 1 to 200 ng mL-1. Matrix effects and recoveries for stable isotope labelled internal standards were evaluated, with most having a coefficient of variation (CV) of less than 15%. Results showed that a majority of the analytes passed both the intra- and interday precision and accuracy criteria. The comparative analysis of human and murine plasma metabolites reveals species-specific variations within the tryptophan metabolic pathway. Notably, murine plasma generally exhibits elevated concentrations of most compounds in this pathway, with the exceptions of kynurenine and quinolinic acid. Moreover, the investigation uncovers noteworthy metabolic disparities between murine visceral and subcutaneous white adipose tissues, with the subcutaneous tissue demonstrating significantly higher concentrations of tryptophan, phenylalanine, tyrosine, and serotonin. The findings also show that even a semi-quantitative method can provide comparable results to quantitative methods from other studies and be effective for assessing metabolites in a complex sample. Overall, this study provides a robust platform to compare human and murine metabolism, providing a valuable insight to future investigations. A validated HRMS method for measuring tryptophan metabolites and related compounds has been developed, with simple sample preparation, successfully applied in human and murine plasma, as well as murine white adipose tissue.
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| 2. |
- Amin, Sidra, et al.
(författare)
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A sensitive enzyme-free lactic acid sensor based on NiO nanoparticles for practical applications
- 2019
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Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 11, s. 3578-3583
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Tidskriftsartikel (refereegranskat)abstract
- A facile and efficient electrochemical sensing platform has been successfully exploited for the first time for the determination of lactic acid using a nickel oxide (NiO) nanoparticle-modified glassy carbon electrode (GCE). Nickel oxide nanoparticles were prepared by a chemical growth method using different quantities of arginine as a soft template. The structural and morphological properties of NiO nanoparticles were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cyclic voltammetry (CV) was used to study the electrochemical properties of various samples. The modified electrode is highly sensitive and presents a linear response over a wide range (0.005–5 mM) of lactic acid concentrations in 0.1 M NaOH. The detection limit for the sensor was found to be 5.7 μM, and it exhibits good stability. Furthermore, the sensor shows excellent selectivity in the presence of common interfering species. The lactic acid sensor showed good viability for lactic acid analysis in real samples (milk, yogurt and red wine) and demonstrated significant advancement in sensor technology for practical applications.
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| 3. |
- Amini, Ahmad, et al.
(författare)
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A protocol for the quality assessment of illegally distributed human growth hormones with respect to identity, purity, endotoxin level and microorganism content
- 2015
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Ingår i: Analytical Methods. - 1759-9660 .- 1759-9679. ; 7:20, s. 8857-8864
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Tidskriftsartikel (refereegranskat)abstract
- Different methods based on MALDI-TOF-MS and double injection capillary zone electrophoresis (DICZE) were used for the identification and purity determination of somatropin in illegally distributed products. During the past few years, more than 200 products suspected to contain somatropin have been analysed. Some of the samples were also subjected to control microorganisms and endotoxins. The identification of somatropin was carried out by peptide mapping using trypsin as the proteolytic enzyme. A double chain peptide cross-linked via a disulfide bond was used as the signature peptide. Capillary electrophoresis in double injection mode was applied to both identification and purity determination of the samples. The identification was based on the comparison between the observed migration time of the reference standard and the calculated migration time of the analyte, being present in the second injection plug. The DICZE provides electrophoretic fingerprints of intact somatropin and the related proteins which facilitate the identification. In addition, some of these samples revealed the presence of microorganisms as well as a high level of endotoxins. Taken together, the doubtful quality of the analysed samples and the microbiological findings represent a serious threat for the consumers and public health.
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| 4. |
- Aminlashgari, Nina, et al.
(författare)
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Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry
- 2011
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 3:1, s. 192-197
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.
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| 5. |
- Antonio Lopez-Lopez, Jose, et al.
(författare)
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Simple hollow fiber liquid membrane based pre-concentration of silver for atomic absorption spectrometry
- 2014
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660. ; 6:5, s. 1462-1467
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Tidskriftsartikel (refereegranskat)abstract
- Silver pollution has gained attention in the last few years because silver is being massively used as a bactericide in self-care, medical and textile products. Difficulties of Ag determination are associated with the very low concentrations in which it is normally found (ng L-1) and the nature of the sample matrix. Standard methods such as liquid-liquid extraction (LLE) are regularly used. Alternatively, liquid phase micro-extraction (LPME) appears to be an environmentally friendly tool for sample treatment that offers higher pre-concentration factors. This allows the determination of ultra-trace levels of silver using standard instrumental techniques such as atomic absorption spectrometry. In this work, a hollow fiber LPME is proposed. Silver pre-concentration has been conducted using tri-isobutylphosphine sulphide (TIBPS) as a carrier from the sample to an acceptor solution through a solvent placed in the fiber pores. Accurel-PP 50/280 fibers with an internal volume of 20 mu L were used for 50 mL samples. After optimization, 0.1 M KNO3 in the sample, 0.1 M TIBPS in dihexyl ether as the organic phase and 1 M Na2S2O3 in the acceptor solution were established. The system offers enrichment factors of 1053 times, a limit of detection of 1.16 ng L-1. This method improves the limit of detection of the most recent liquid micro-extraction methods for silver pre-concentration coupled with GFAAS, being in this case comparable to ICP-MS detection based techniques.
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| 6. |
- Beal, Alexandra, et al.
(författare)
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A new analytical method for lead determination in atmospheric particulate matter by a combination of ultrasound-assisted extraction and supramolecular solvent preconcentration
- 2018
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 10:30, s. 3745-3753
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Tidskriftsartikel (refereegranskat)abstract
- Air pollution by lead, even in small concentrations, can cause serious health effects. In the atmosphere this element can generally be found in particulate matter (PM), and in general in small concentrations. This work proposes the development of an analytical method for lead determination in inhaled PM based on ultrasound-assisted extraction with subsequent supramolecular solvent based dispersive liquid-liquid microextraction (SM-DLLME), using reverse micelles of dodecanoic acid as an extractor dispersed in a continuous phase of tetrahydrofuran (THF)/water. The rich phase was then analyzed by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) coupled on-line to a flow injection analysis (FIA). An analytical curve in the range of 15.0-200.0 μg L-1 (R2 = 0.999), an enrichment factor of 18.1 times and the limits of detection (LOD) and quantification (LOQ) equal to 3.7 and 11.3 μg L-1, respectively, were obtained. The accuracy of the method was successfully attested by comparing with EDX analysis through the paired t-test at a confidence level of 95%. The amount of lead determined in the samples of PM collected in different environments varied from 19.3 to 94.8 ng m-3.
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| 7. |
- Bergman, Nina, et al.
(författare)
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Quantitative determination of the Ru(bpy)(3)(2+) cation in photochemical reactions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
- 2014
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 6:21, s. 8513-8518
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Tidskriftsartikel (refereegranskat)abstract
- The coordination compound of Ru(II) with three 2,2'-bipyridine ligands possesses a potent photosensitization capacity for electron- and energy-transfer processes. In combination with salts of peroxydisulfate acid as sacrificial electron acceptors, Ru(bpy)(3)(2+) is widely used for photocatalytic oxidative transformations in organic synthesis and water splitting. The drawback of this system is that bipyridine degrades under the resulting strongly oxidative conditions, the concentration of Ru(bpy)(3)(2+) diminishes, and the photocatalytic reaction eventually stops. A commonly employed assay for the determination of Ru(bpy)(3)(2+), UV-Vis spectroscopy, has low selectivity and does not distinguish between the intact complex and its decayed forms. Here, we report a matrix assisted laser desorption/ionisation mass spectrometric method for the quantitative analysis of Ru(bpy)(3)(2+) in photochemical reaction mixtures. The developed method was successfully used for the determination of intact Ru(bpy)(3)(2+) during the course of the water photooxidation reaction. The significant difference between the results of MALDI MS and UV-Vis analyses was observed.
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| 8. |
- Boström, Marja L., et al.
(författare)
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A specific, highly enriching and "green" method for hollow fiber liquid phase microextraction of ionizable pharmaceuticals from fish tissue
- 2014
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660. ; 6:15, s. 6031-6037
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Tidskriftsartikel (refereegranskat)abstract
- Ionizable pharmaceuticals are a class of emerging contaminants that pose a challenge to analytical chemistry due to their low environmental concentrations. To measure such low concentrations in organism tissue, e.g. fish muscle, specific extraction techniques minimizing co-extraction and interference alongside providing high enrichment of the compounds are needed. In this study we present a technique using hollow fiber liquid phase microextraction which is selective and highly enriching due to a pH gradient across a selective membrane, trapping ions in the extract. Microextraction minimizes the use of organic solvents, thereby making the technique "green". We used high volume pharmaceuticals for method development, specifically, the weak acids ketoprofen, naproxen, diclofenac and ibuprofen, and the weak bases fluoxetine and sertraline. Lyophilized tissue extraction gave higher enrichment than fresh tissue extraction and concentration enrichment factors ranged from 1900 to 3000 times. Method detection limits with the analysis instruments used in this study were for ketoprofen, 0.23 ng g(-1) fish tissue; naproxen, 0.32 ng g(-1) fish tissue; diclofenac, 0.12 ng g(-1) fish tissue; ibuprofen, 0.34 ng g-1 fish tissue; fluoxetine, 13 ng g-1. fish tissue and sertraline, 23 ng g(-1) fish tissue. All analytes were successfully detected in tissue from fish exposed live via spiked water. The resulting extraction parameters shown in this study suggest the developed technique to be a useful work up method for extensive environmental data collection as well as for toxicokinetic studies.
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| 9. |
- Chen, Changer Long, et al.
(författare)
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Determination of fragrance ingredients in fish by ultrasound-assisted extraction followed by purge & trap
- 2017
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 9:15, s. 2237-2245
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Tidskriftsartikel (refereegranskat)abstract
- Fragrance materials are widely used in household and personal care products in applications that can lead to emissions into the aquatic environment. Assessing the potential of fragrance materials to bioaccumulate in fish in in vivo laboratory studies requires a reliable analytical method for determining the concentrations of chemical substances in fish tissue. Here, we present an analytical method for simultaneously measuring a group of model chemicals that are representative of chemicals found in fragrance materials in rainbow trout. This method involves ultrasound-assisted extraction (UAE) followed by enrichment of the fragrance ingredients using a purge & trap system. Nine fragrance ingredients including semi-volatile and volatile compounds were selected as model substances for method development. Homogenised whole rainbow trout subsamples were spiked with these nine model fragrance ingredients, hexachlorobenzene (HCB) and 2,2',5,5'-tetrachlorobiphenyl (PCB52). The targeted chemicals were extracted from the fish tissue using acetonitrile in an ultrasonic bath; after solvent exchange to hexane, they were extracted into the gas phase by heating the samples and purging with nitrogen and trapped on a solid-phase extraction (SPE) cartridge. Finally, these chemicals were eluted with hexane from the SPE column and analysed using gas chromatography-mass spectrometry (GC-MS). The proposed method has been evaluated for blanks, spiked recoveries and precision, which are all acceptable. We believe that the method presented here is generally applicable for analysis of acid-sensitive volatile and semi-volatile organic chemicals in fish and provides the basis to conduct in vivo bioaccumulation studies of fragrance materials.
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| 10. |
- Comina, German, et al.
(författare)
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A 3D printed device for quantitative enzymatic detection using cell phones
- 2016
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Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 8:32, s. 6135-6142
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Tidskriftsartikel (refereegranskat)abstract
- A disposable device for quantitative enzymatic detection capable of coupling illumination and image readouts from cell phones is demonstrated. The device integrates a calibration range for glutamate detection, utilizes the phone screen as a light source, and provides the necessary actuation for autonomous operation. Custom made optics required to couple to the cell phone camera is accomplished using affordable stereolithography (SLA) 3D printers. The described method does not involve polishing, requires only two steps from design to implementation, and can be locally applied to 3D printed lab-on-a-chip (LOC) prototypes, using the same materials. Optical finishing and dimensional variability within 2% were achieved, supporting entirely arbitrary geometries for elements larger than 400 mm in radius. Representative fabrication times and costs were 20 min and $0.50 USD per prototype.
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