| 511. |
- Titaley, Ivan, 1990-, et al.
(författare)
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Automating data analysis for two-dimensional gas chromatography/time-of-flight mass spectrometry non-targeted analysis of comparative samples
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1541, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- Non-targeted analysis of environmental samples, using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC x GC/ToF-MS), poses significant data analysis challenges due to the large number of possible analytes. Non-targeted data analysis of complex mixtures is prone to human bias and is laborious, particularly for comparative environmental samples such as contaminated soil pre- and post-bioremediation. To address this research bottleneck, we developed OCTpy, a Python (TM) script that acts as a data reduction filter to automate GC x GC/ToF-MS data analysis from LECO (R) ChromaTOF (R) software and facilitates selection of analytes of interest based on peak area comparison between comparative samples. We used data from polycyclic aromatic hydrocarbon (PAH) contaminated soil, pre- and post-bioremediation, to assess the effectiveness of OCTpy in facilitating the selection of analytes that have formed or degraded following treatment. Using datasets from the soil extracts pre- and post-bioremediation, OCTpy selected, on average, 18% of the initial suggested analytes generated by the LECO (R) ChromaTOF (R) software Statistical Compare feature. Based on this list, 63-100% of the candidate analytes identified by a highly trained individual were also selected by OCTpy. This process was accomplished in several minutes per sample, whereas manual data analysis took several hours per sample. OCTpy automates the analysis of complex mixtures of comparative samples, reduces the potential for human error during heavy data handling and decreases data analysis time by at least tenfold. (C) 2018 Elsevier B.V. All rights reserved.
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| 512. |
- Tollbäck, Johanna, et al.
(författare)
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Air sampling with Empore solid phase extraction membranes and online single-channel desorption/liquid chromatography/mass spectrometry analysis : Determination of volatile and semi-volatile organophosphate esters
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1129:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- A method for determining organophosphate esters in air samples using C8 Empore solid phase extraction (SPE) membranes has been developed. After the sampling the analytes trapped in the membrane are completely desorbed with methanol, using an extraction cell connected online to the organic modifier channel of a HPLC gradient pump. The addition of water to the mobile phase prior to analytical chromatography ensures that the analytes are refocused and efficiently separated. Sampling with Empore SPE membranes enables the collection of analytes in both the vapour phase and particulate matter. During the air sampling procedure no losses were observed after 24 h of sampling, yielding a total volume of 14.4 m3, even for the most volatile compound used in this investigation (trimethylphosphate). Complete desorption was observed for all the organophosphate esters and recoveries were greater than 95%, with a relative standard deviation of less than 8%. The limits of detection ranged between 0.4 and 19 pg/m3. The effect of particulate matter on the extraction efficiency was investigated in detail by spiking the membranes with reference standard material. It was also found that the SPE membranes could be stored for at least 5 days at room temperature without any evidence of loss. The efficacy of the method was verified using real samples from different common indoor environments. Interestingly, significant quantities of several phosphate esters were found in a NIST standard reference material (urban dust, SRM 1649a).
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| 513. |
- Tollbäck, Johanna, et al.
(författare)
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Determination of the flame retardant tetrabromobisphenol A in air samples by liquid chromatography-mass spectrometry.
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1104:1-2, s. 106-12
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Tidskriftsartikel (refereegranskat)abstract
- An original method based on LC-MS for determination of the flame retardant tetrabromobisphenol A (TBBPA) in air is presented, as an alternative to the traditionally used GC-MS. The soft ionization in LC-MS makes it possible to monitor the intact molecule and to use 13C-labelled TBBPA as an internal surrogate standard, two features that improve both accuracy and precision of the analyses. Comparison of different acquisition modes in electrospray ionization showed that the lowest detections limit, 3.1 pg TBBPA injected, was obtained in SIM monitoring the molecular ions 542.7/544.7. A fragmentation pathway of TBBPA in LC-ESI-MS is suggested. The only sample clean-up steps required are solvent reduction and filtration of the sample extract. Recoveries were 93% at a 30 ng level and 75% at 3 ng. The new method was tested by analyses of air samples collected at a recycling plant for electronic equipment. The amount of TBBPA found was 13.8 ng/m3 with an RSD of 5.9%. Furthermore, it was found that TBBPA in a standard solution could be partially debrominated, if not carefully protected from light during storage.
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| 514. |
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| 515. |
- Tong, XM, et al.
(författare)
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Computer simulation of particle separation based on non-equilibrium swelling
- 1999
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Ingår i: JOURNAL OF CHROMATOGRAPHY A. - : ELSEVIER SCIENCE BV. - 0021-9673. ; 831:1, s. 51-62
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Steric/hyperlayer field-flow fractionation (FFF) is an established analytical technique for separating and characterizing particles in the 1-100 mu m diameter range. The separation can be based on differences in size, density, shape and mechanical propert
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| 516. |
- Ullah, Shahid, 1977-, et al.
(författare)
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Simultaneous determination of perfluoroalkyl phosphonates, carboxylates, and sulfonates in drinking water
- 2011
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1218:37, s. 6388-6395
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Tidskriftsartikel (refereegranskat)abstract
- A trace analytical method based on high performance liquid chromatography coupled to quadrupole time-of-flight high resolution mass spectrometry was developed for simultaneous determination of perfluoroalkyl phosphonates (PFPAs, carbon chain lengths C6,8,10), perfluoroalkyl carboxylates (PFCAs. C5-12), and perfluoroalkyl sulfonates (PFSAs. C4,6,8,10) in drinking water (tap water). Analytes were enriched on a mixed mode co-polymeric sorbent (C8 + quaternary amine) using solid phase extraction. Chromatographic separation was achieved on a Zorbax Extend C18 reversed phase column using a mobile phase gradient consisting of water, methanol, and acetonitrile containing 2 mM ammonium acetate and 5 mM 1-methyl piperidine. The mass spectrometer was operated in electrospray negative ion mode. Use of 1-methyl piperidine in the mobile phase resulted in a significant increase in instrument sensitivity for PFPAs through improved chromatographic resolution, background suppression, and increased ionization efficiency. Method detection limits for extraction of 500 mL tap water were in the ranges of 0.095-0.17 ng/L, 0.027-0.17 ng/L, and 0.014-0.052 ng/L for PFPAs. PFCAs, and PFSAs, respectively. Whole method recoveries at a spiking level of 0.5 ng/L to 500 mL HPLC grade water were 40-56%, 56-97%, and 55-77% for PFPAs, PFCAs. and PFSAs, respectively. A matrix effect (signal enhancement) was observed in the detection of PFPAs in tap water extracts, leading to calculated recoveries of 249-297% at a 0.5 ng/L spiking level. This effect resulted in an additional improvement of method sensitivity for PFPAs. To compensate for the matrix effect. PFPAs in tap water were quantified using matrix-matched and extracted calibration standards. The method was successfully applied to the analysis of drinking water collected from six European countries. PFPAs were not detected except for perfluorooctyl phosphonate (PFOPA) at close to the detection limit of 0.095 ng/L in two water samples from Amsterdam, the Netherlands. Highest levels were found for perfluorobutane sulfonate (PFBS, 18.8 ng/L) and perfluorooctanoate (PFOA, 8.6 ng/L) in samples from Amsterdam as well as for perfluorooctane sulfonate (PFOS, 8.8 ng/L) in tap water from Stockholm, Sweden.
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| 517. |
- Ullsten, Sara, et al.
(författare)
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Urine profiling using capillary electrophoresis-mass spectrometry and multivariate data analysis
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1:1117, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the development of a general and fast method for metabolic profiling of urine, using capillary electrophoresis-electrospray ionisation mass spectrometry (CE-ESIMS) and multivariate data analysis (DA). Human urine samples collected before and after ingestion of paracetamol were analysed at acidic and basic CE conditions, using both positive and negative ESI-MS detection. Analysis of the entire resulting data set, with no prior knowledge of the target compounds, using pair-wise 'fuzzy' correlation and eigenvalue analysis enabled the samples to be discriminated between on the basis of blank urine and urine collected after drug intake. By generating two-dimensional loadings plots, it was also possible to identify the m/z values of the substances responsible for the differentiation between control and dosed samples.
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| 518. |
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| 519. |
- Valdés, Alberto, et al.
(författare)
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Shotgun proteomic analysis to study the decrease of xenograft tumor growth after rosemary extract treatment
- 2017
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1499, s. 90-100
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Tidskriftsartikel (refereegranskat)abstract
- The antiproliferative activity of Rosemary (Rosmarinus officinalis) has been widely studied in different in vitro and in vivo models, which demonstrate that rosemary extracts inhibit the cellular proliferation due to its ability to interact with a wide spectrum of molecular targets. However, a comprehensive proteomics study in vivo has not been carried out yet. In the present work, the effects of rosemary extract on xenograft tumor growth has been studied and, for the first time, a shotgun proteomic analysis based on nano-LC-MS/MS together with stable isotope dimethyl labeling (DML) has been applied to investigate the global protein changes in vivo. Our results show that the daily administration of a polyphenol-enriched rosemary extract reduces the progression of colorectal cancer in vivo with the subsequent deregulation of 74 proteins. The bioinformatic analysis of these proteins indicates that the rosemary extract mainly alters the RNA Post-Transcriptional Modification, the Protein Synthesis and the Amino Acid Metabolism functions and suggests the inactivation of the oncogene MYC. These results demonstrate the high utility of the proposed analytical methodology to determine, simultaneously, the expression levels of a large number of protein biomarkers and to generate new hypothesis about the molecular mechanisms of this extract in vivo.
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| 520. |
- van Tricht, Ewoud, et al.
(författare)
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Fast, selective and quantitative protein profiling of adenovirus-vector based vaccines by ultra-performance liquid chromatography
- 2018
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Ingår i: Journal of Chromatography A. - : ELSEVIER SCIENCE BV. - 0021-9673 .- 1873-3778. ; 1581-1582, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- A method for the quantitative determination of the protein composition of adenovirus-vector based vaccines was developed. The final method used RP-UPLC with UV absorbance detection, a C4 column (300 angstrom, 1.7 mu m, 2.1 x 150 mm), and a water- acetonitrile (ACN) gradient containing trifluoroacetic acid (TFA) as ion-pairing agent. The chromatographic resolution between the various adenovirus proteins was optimized by studying the effect of the TFA concentration and the column temperature, applying a full factorial design of experiments. A reproducible baseline separation of all relevant adenovirus proteins could be achieved within 17 min run time. Samples containing adenovirus particles could be directly injected into the UPLC system without sample pretreatment. The viruses reproducibly dissociate into proteins in the UPLC system upon contact with the mobile phase containing ACN. The new RP-UPLC method was successfully validated for protein profiling and relative quantification of proteins in vaccine products based on adenovirus vector types 26 and 35. The intermediate precision of the relative peak areas of all proteins was between 1% and 14% RSD, except for the peak assigned to protein V (26% RSD). The method proved to be stability indicating with respect to thermal and oxidation stress of the adenovirus-vector based vaccine and was successfully implemented for the characterization of adenovirus-based products.
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