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Mass Spectrometry Detection (mass + spectrometry_detection)
Selected AbstractsPerchlorate assessment of the Nakdong and Yeongsan watersheds, Republic of KoreaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2007Oscar Quiñones Abstract The objective of the present study was to conduct a preliminary assessment for perchlorate in surface water, drinking water, and wastewater treatment plant effluent samples obtained from the Nakdong and Yeongsan watersheds in the Republic of Korea. Samples were analyzed for perchlorate using ion chromatography with suppressed conductivity detection (IC-CD) and/or liquid chromatography with tandem mass spectrometry detection (LC-MS/MS). Method reporting limits were 5.0 ,g/L for IC-CD and 0.05 ,g/L for LC-MS/MS analysis. At perchlorate levels above 5.0 ,g/L, IC-CD and LC-MS/MS provided comparable results. The levels of perchlorate detected in the samples procured from the Yeongsan watershed were <5.0 ,g/L in each case. However, Nakdong watershed samples contained perchlorate at levels up to 60 ,g/L. The highest concentrations of perchlorate were found in surface water samples, although drinking water contained perchlorate at concentrations up to 35 ,g/L. In a subset of samples analyzed by LC-MS/MS, chlorate and bromate also were detected at concentrations ranging from <0.10 to 44 ,g/L and <0.10 to 2.6 ,g/L, respectively. To the best of the authors' knowledge, this is the first perchlorate assessment reported for water sources in the Republic of Korea. [source] Single run measurements of drug-protein binding by high-performance frontal analysis capillary electrophoresis and mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005Hong Wan A novel drug-protein binding measurement method based on high-performance frontal analysis and capillary electrophoresis (HPFA/CE) is presented. A single run measurement approach is proposed to circumvent utilization of a calibration curve that is often performed with HPFA. A sensitive mass spectrometer is applied as a detector enabling the measurement of in vitro protein binding at lower drug concentrations. Unbound free fraction and binding constants can be determined by a single run measurement by consecutive injections of an internal drug standard, a buffer plug and a drug-protein mixture. Effects of injection volumes on peak height and plateau profile were investigated in two different separation systems, non-volatile buffer and volatile buffer, with UV and mass spectrometry detection, respectively. A simplified one-to-one binding model is employed to evaluate the proposed method by using both single and multiple drug concentrations to measure the unbound free fraction and calculate the binding constants of some selected compounds. The method is suitable for rapid and direct screening of the binding of a drug to a specific protein or drug-plasma protein binding. Copyright © 2005 John Wiley & Sons, Ltd. [source] Determination of , -tocopherol in infant foods by liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003Andras Kalman A novel, sensitive and specific method for the quantification of , -tocopherol in two infant foods (milk and cereals) using liquid chromatography on-line with positive atmospheric pressure chemical ionisation mass spectrometry detection (LC/APCI-MS) has been developed. The samples were first saponified in order to eliminate fats and to transform tocopherol esters into free tocopherol, followed up by a liquid,liquid extraction of the analyte in petroleum benzine/diisopropyl ether (75:25, v/v) prior to injection onto the LC system. For the quantification, deuterium-labelled tocopherol was used as internal standard and the samples were monitored in selected ion monitoring (SIM) mode. Calibration curves between 1,40,,g/mL of , -tocopherol showed a good linear correlation (r2,=,0.99994), and the detection limit was determined to be 2.5,ng/mL. The within-day and between-day precision were determined for several dietetic infant formulae and certified reference samples, and found to be below 3.5%. The accuracy determined on a Nestlé reference sample (milk powder) was calculated to be 115.2,±,1.2%, which confirms the robustness of the proposed method. This study shows that single quadrupole LC/MS can be applied for the quantification of vitamins in food and the method offers better sensitivity and selectivity than traditional method such as LC-UV. This would simplify the preparation of the food samples and consequently enhance the vitamin analysis throughput in the food area. Copyright © 2003 John Wiley & Sons, Ltd. [source] Speciation of essential and toxic elements in edible mushrooms: size-exclusion chromatography separation with on-line UV,inductively coupled plasma mass spectrometry detectionAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2004Rodolfo G. Wuilloud Abstract Size-exclusion liquid chromatography was coupled to UV and inductively coupled plasma mass spectrometry (ICP-MS) for detection to perform elemental speciation studies on different edible mushrooms. Molecular weight (MW) distribution patterns of several elements among different fractions present in various edible mushrooms are presented. The association of the elements with the high and low MW fractions was observed using sequential detection by UV and ICP-MS. Separation was performed using a Superdex 75 column. Variability of the fractionation patterns with three different extraction media (0.05 mol l,1 NaOH; 0.05 mol l,1 HCl; hot water at 60°C) was evaluated for mushroom species. A comparative elemental speciation study was performed in order to determine the differences in the fractionation patterns of silver, arsenic, cadmium, mercury, lead, and tin in Boletus edulis, Agaricus bisporus, and Lentinus edodes. Differences in the fractionation patterns of the elements were found to depend on the mushroom species and the extraction medium. Most of the elements were associated with high mw fractions. It was not possible to assess the trace metal contributions from the mushroom growth media. Copyright © 2004 John Wiley & Sons, Ltd. [source] Bioanalysis of pentoxifylline and related metabolites in plasma samples through LC-MS/MSBIOMEDICAL CHROMATOGRAPHY, Issue 6 2010Daniela Iuliana Sora Abstract Analytical aspects related to the assay of pentoxifylline (PTX), lisofylline (M1) and carboxypropyl dimethylxanthine (M5) metabolites are discussed through comparison of two alternative analytical methods based on liquid chromatography separation and atmospheric pressure electrospray ionization tandem mass spectrometry detection. One method is based on a ,pure' reversed-phase liquid chromatography mechanism, while the second one uses the additional polar interactions with embedded amide spacers linking octadecyl moieties to the silicagel surface (C-18 Aqua stationary phase). In both cases, elution is isocratic. Both methods are equally selective and allows separation of unknowns (four species associated to PTX, two species associated to M1) detected through specific mass transitions of the parent compounds and owning respective structural confirmation. Plasma concentration,time patterns of these compounds follow typical metabolic profiles. It has been advanced that in-vivo formation of conjugates of PTX and M1 is possible, such compounds being cleaved back to the parent ones within the ion source. The first method was associated with a sample preparation procedure based on plasma protein precipitation by strong organic acid addition. The second method used protein precipitation by addition of a water miscible organic solvent. Both analytical methods were fully validated and used to assess bioequivalence between a prolonged release generic formulation and the reference product, under multidose and single dose approaches. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of caudatin-2,6-dideoxy-3 -O- methy- , - d -cymaropyranoside in rat plasma using liquid chromatography,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 6 2008Yunru Peng Abstract A selective, sensitive and rapid liquid chromatography,tandem mass spectrometry method has been developed for the determination of caudatin-2,6-dideoxy-3 -O- methy- , - d -cymaropyranoside (CDMC) in rat plasma. This method involves a plasma clean-up step using liquid,liquid extraction, followed by LC separation and positive electrospray ionization mass spectrometry detection (LC/ESI-MS/MS). Chromatographic separation of the analytes was achieved using a C18 column with a mobile phase of acetonitrile and water (70:30, v/v) at a flow rate of 1.0 mL/min. Low energy collision tandem mass spectrometric analysis (CID-MS/MS) using the multiple reaction monitoring (MRM) mode was used for analyte quantification. For the MRM analysis of CDMC, the following transition at m/z 658.4 , 529.6 derived from the protonated molecule [M + Na]+. A calibration curve was linear in the 5,500 ng/mL range for CDMC, and the limit of detection was 5 ng/mL. The inter- and intra-day precisions (RSD) were ,8.5 and ,9.1%, respectively. The accuracy (RE) was ± 10.9%. The novel developed LC/ESI-MS/MS method was successfully applied to pharmacokinetic studies of CDMC after oral administration to rats. The total chromatographic run time of this method was 5.0 min per sample, allowing for analysis of a large number of samples per batch. Copyright © 2008 John Wiley & Sons, Ltd. [source] Quantitative gas chromatography/time-of-flight mass spectrometry: a reviewBIOMEDICAL CHROMATOGRAPHY, Issue 7 2007Leah N. Williamson Abstract Time-of-flight (TOF) instruments have recently gained popularity in quantitative analyses. Normally, TOF mass spectrometers are used for accurate mass measurements for empirical formula verification. However, over the past decade, they have been used quantitatively as well. Because of the fast separations and narrow peaks that result from gas chromatography separations, scanning mass spectrometers are not ideal detectors. TOF mass spectrometers, however, have the ability to collect spectra at a faster rate. Two-dimensional gas chromatography has also been introduced to further resolve peaks from complex matrices. Two-dimensional gas chromatography results in a faster separation as well as narrower peaks. This paper reviews the methods currently in the literature for the quantitation of compounds using one- and two-dimensional gas chromatography and TOF mass spectrometry detection. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effect of varying feedstock,pretreatment chemistry combinations on the formation and accumulation of potentially inhibitory degradation products in biomass hydrolysatesBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Bowen Du Abstract A variety of potentially inhibitory degradation products are produced during pretreatment of lignocellulosic biomass. Qualitative and quantitative interrogation of pretreatment hydrolysates is paramount to identifying potential correlations between pretreatment chemistries and microbial inhibition in downstream bioconversion processes. In the present study, corn stover, poplar, and pine feedstocks were pretreated under eight different chemical conditions, which are representative of leading pretreatment processes. Pretreatment processes included: 0.7% H2SO4, 0.07% H2SO4, liquid hot water, neutral buffer solution, aqueous ammonia, lime, lime with oxygen pressurization, and wet oxidation. Forty lignocellulosic degradation products resulting from pretreatment were analyzed using high performance liquid chromatography in combination with UV spectroscopy or tandem mass spectrometry detection (HPLC-PDA-MS/MS) and ion chromatography (IC). Of these compounds, several have been reported to be inhibitory, including furfural, hydroxymethyl furfural, ferulic acid, 3,4-dihydroxybenzaldehyde, syringic acid among others. Formation and accumulation of monitored compounds in hydrolysates is demonstrated to be a function of both the feedstock and pretreatment conditions utilized. Biotechnol. Bioeng. 2010;107: 430,440. © 2010 Wiley Periodicals, Inc. [source] Simultaneous determination of eight major steroids from Polyporus umbellatus by high-performance liquid chromatography coupled with mass spectrometry detectionsBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Ying-yong Zhao Abstract Polyporus umbellatus is a widely used diuretic herbal medicine. In this study, a high-performance liquid chromatography coupled with atmospheric pressure chemical ionization,mass spectrometric detection (HPLC-APCI-MS) method was developed for qualitative and quantitative analysis of steroids, as well as for the quality control of Polyporus umbellatus. The selectivity, reproducibility and sensitivity were compared with HPLC with photodiode array detection and evaporative light scattering detection (ELSD). Selective ion monitoring in positive mode was used for qualitative and quantitative analysis of eight major components and ,-ecdysterone was used as the internal standard. Limits of detection and quantification fell in the ranges 7,21 and 18,63 ng/mL for the eight analytes with an injection of 10 µL samples, and all calibration curves showed good linear regression (r2 > 0.9919) within the test range. The quantitative results demonstrated that samples from different localities showed different qualities. Advantages, in comparison with conventional HPLC,diode array detection and HPLC-ELSD, are that reliable identification of target compounds could be achieved by accurate mass measurements along with characteristic retention time, and the great enhancement in selectivity and sensitivity allows identification and quantification of low levels of constituents in complex Polyporus umbellatus matrixes. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||