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Ion Monitoring (ion + monitoring)
Kinds of Ion Monitoring Terms modified by Ion Monitoring Selected AbstractsIn vitro stability of triclosan in dentifrice under simulated use conditionINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2007Z. Hao Synopsis Triclosan has been formulated into a dentifrice at a 0.3% level to enhance the antibacterial function of the dentifrice, to improve oral health and to decrease the daily malodor inside the mouth cavity. The hypothesis that chloroform may be generated from triclosan when contacted with chlorinated drinking water has challenged our guarantee of safe use of triclosan in oral care products, especially in Colgate Total® toothpaste. Currently, there was no available analytical method to detect chloroform levels under the use conditions expected during daily tooth brushing. To fill this gap and to continue guaranteeing that our customers can safely use Colgate Total® toothpaste products, a gas chromatography,single ion monitoring,mass spectrometry method for detecting chloroform in artificial saliva media has been developed. The limit of detection (LOD) and limit of quantitation are about 41 and 130 ppb, respectively. This LOD level is lower than the current Environmental Protection Agency trihalomethanes contamination limit, which is required for our daily drink water. Our in vitro study indicated that Colgate Total® does not form detectable chloroform levels (41 ppb) over the range of expected consumer-brushing times while using normal chlorinated drinking water. Résumé Un dentifrice contenant une concentration de 0.3% de Triclosan a été formulé dans le but de renforcer les propriétés antibactériennes du produit, d'améliorer l'hygiène buccale et de diminuer les mauvaises odeurs quotidiennes de la cavité buccale. L'hypothèse que du chloroforme peut se former à partir du Triclosan au contact de l'eau douce chlorée jette un doute sur la garantie de sécurité d'utilisation du Triclosan dans les produits oraux, en particulier dans la pâte dentifrice Colgate Total®. On ne dispose actuellement d'aucune méthode analytique permettant de détecter le chloroforme dans des conditions habituelles d'utilisation qui correspondent au brossage quotidien des dents. Pour y remédier et pour continuer à garantir à nos clients la sécurité d'utilisation de la pâte dentifrice Colgate Total®, une méthode GC-SIM-MS capable de détecter le chloroforme dans une salive artificielle a été développée. La limite de détection (LOD) et la limite de quantification (LOQ) sont respectivement d'environ de 41 et 130 ppb. Cette valeur de LOD est inférieure à la limite de contamination en trihalométhane requise pour l'eau douce journalière par l'Environnemental Protection Agency (EPA). Notre étude in vitro montre que Colgate Total® ne génère pas de chloroforme à une concentration détectable (41 ppb) pendant la durée requise d'un brossage avec l'utilisation d'eau potable chlorée. [source] Determination and Confirmation of Chloramphenicol Residues in Swine Muscle and LiverJOURNAL OF FOOD SCIENCE, Issue 1 2002T.L. Li ABSTRACT: Average high-performance liquid chromatography (HPLC) recoveries of chloramphenicol (CAP) in swine muscle and liver ranged from 91.3 to 94.2% and 93.1 to 103.7%, respectively, with coefficients of variation ranging from 1.4 to 4.3% and 1.1 to 11.2% for each tissue sample. The method described was repeatable and reproducible in swine muscle and liver, with a limit of quantification of 15 ng/mL and a limit of detection estimated at 5 ng/mL. The limit of identification of CAP was 25 ng/mL, 5ng/mL, and 20 ng/mL for HPLC/PDA, GC/MS selected ion monitoring (SIM), and LC/MS analysis, respectively. [source] A validated method for the determination of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2006Insook Kim Abstract A liquid chromatographic-mass spectrometric method for the simultaneous determination of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma was developed and validated. Analytes and deuterated internal standards were extracted from human plasma using solid-phase extraction and analyzed by liquid chromatography/atmospheric pressure chemical ionization-mass spectrometric detection with selected ion monitoring (SIM). Limits of detection and quantification were 1.0 and 2.5 ng/ml, respectively, for all analytes. Linearity ranged from 2.5 to 500 ng/ml of human plasma using a weighting factor of 1/x; correlation coefficients for the calibration curves were > 0.99. Intra- and inter-assay precision and accuracy were < 15.0%. Recoveries were 108.2,110.8% nicotine, 95.8,108.7% cotinine, 90.5,99.5% trans -3,-hydroxycotinine, and 99.5,109.5% norcotinine. The method was also partially validated in bovine serum, owing to the difficulty of obtaining nicotine-free human plasma for the preparation of calibrators and quality control (QC) samples. This method proved to be robust and accurate for the quantification of nicotine, cotinine, trans -3,-hydroxycotinine, and norcotinine in human plasma collected in clinical studies of acute nicotine effects on brain activity and on the development of neonates of maternal smokers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Increased oxidative damage in nuclear and mitochondrial DNA in mild cognitive impairmentJOURNAL OF NEUROCHEMISTRY, Issue 3 2006Jianquan Wang Abstract Increasing evidence suggests that oxidative damage is associated with normal aging and several neurodegenerative diseases. Mild cognitive impairment (MCI), the phase between normal aging and early dementia, is a common problem in the elderly with many subjects going on to develop Alzheimer's disease (AD). Although increased DNA oxidation is observed in the AD brain, it is unclear when the oxidative damage begins. To determine if DNA oxidation occurs in the brain of subjects with MCI, we quantified multiple oxidized bases in nuclear and mitochondrial DNA isolated from frontal, parietal and temporal lobes and cerebellum of short post-mortem interval autopsies of eight amnestic patients with MCI and six age-matched control subjects using gas chromatography/mass spectrometry with selective ion monitoring. We found statistically significant elevations (p < 0.05) of 8-hydroxyguanine, a widely studied biomarker of DNA damage, in MCI nuclear DNA from frontal and temporal lobe and in mitochondrial DNA from the temporal lobe compared with age-matched control subjects. Levels of 8-hydroxyadenine and 4,6-diamino-5-formamidopyrimidine were significantly elevated in nuclear DNA from all three neocortical regions in MCI. Statistically significant elevations of 4,6-diamino-5-formamidopyrimidine were also observed in mitochondrial DNA of MCI temporal, frontal and parietal lobes. These results suggest that oxidative damage to nuclear and mitochondrial DNA occurs in the earliest detectable phase of AD and may play a meaningful role in the pathogenesis of this disease. [source] Capillary high performance liquid chromatography coupled with electrospray ionization mass spectrometry for rapid analysis of pinane monoterpene glycosides in Cortex MoutanJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2008Yue Song Abstract In this study, a rapid and reliable assay has been developed for quantification of pinane monoterpene glycosides in Cortex Moutan; it is based on capillary high performance liquid chromatography coupled with electrospray ionization mass spectrometry (capillary HPLC,ESI MS). This method utilizes capillary HPLC for the separation of seven pinane monoterpene glycosides in a methanol extract of the botanical sample followed by negative ion electrospray ionization and single ion monitoring (SIM). The compounds of interest in the sample were unambiguously identified on the basis of information about retention time and quasi-molecular ions ([M,H],) or adduct ions ([M+HCOO],). Validation parameters of the method were established. The linearity range was 1.01,105.5 ,g/mL with the square of correlation coefficients lying in the range of 0.9965,0.9997, limits of detection were on the fmol level, the average recoveries varied between 91.8 and 101.0%, and good precision values (RSD, 1.2,4.91%) for peak area were obtained. After validation, the applicability of the method for determination of these pinane monoterpene glycosides in Cortex Moutan has been demonstrated. [source] Determination of residues of endosulfan in human blood by a negative ion chemical ionization gas chromatographic/mass spectrometric method: impact of long-term aerial spray exposurePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2003Atmakuru Ramesh Abstract A new and sensitive analytical method using negative ion chemical ionization gas chromatography/mass spectrometry in selective ion monitoring (SIM) mode has been developed for the determination of residues of endosulfan in the human blood. The residues of endosulfan are extracted from whole blood samples without separating the serum by the addition of 60% sulfuric acid at 10,°C followed by partition with hexane,+,acetone (9,+,1 by volume). The total endosulfan is quantified as the sum of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in SIM mode. The mass-fragment ions used for this purpose that are monitored for in SIM mode include endosulfan diol: 95, 169, 214, 313, alpha-endosulfan: 99, 242, 270, 406, beta-endosulfan: 99, 242, 270, 406, and endosulfan sulfate: 97, 353, 386. Recovery experiments were conducted at the concentration range 1.0,100,pg,ml,1. Results showed 112,98% recovery of total endosulfan from the whole blood samples. The relative standard deviation was 1.49,2.68%. The method was found to be highly sensitive in quantifying endosulfan residues down to the 0.1,pg,ml,1 level. Conversion of endosulfan to endosulfan diol was found to be less than 0.1% under the conditions used. The results were compared with published data. The applications of the analytical method for the determination of endosulfan residues in real samples was tested by analyzing 106 human blood samples collected from a population living in Padre village, Kasargode District, Kerala, India, where aerial spraying of endosulfan has been a common agricultural practice over the years. The results showed that none of the blood samples contained residues of endosulfan (alpha-endosulfan,+,beta-endosulfan,+,endosulfan sulfate) or endosulfan diol. The results were confirmed by the detection of the appropriate amounts in a number of these samples which had subsequently been spiked with endosulfan. © 2003 Society of Chemical Industry [source] Interference of chlorofluorocarbon (CFC)-containing inhalers with measurements of volatile compounds using selected ion flow tube mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2009Michael J. Epton Selected ion flow tube mass spectrometry (SIFT-MS) is a sensitive technique capable of measuring volatile compounds (VCs) in complex gas mixtures in real time; it is now being applied to breath analysis. We investigated the effect of inhalers containing chlorofluorocarbons (CFCs) on the detection and measurement of haloamines in human breath. SIFT-MS mass scans (MS) and selected ion monitoring (SIM) scans were performed on three healthy non-smoking volunteers before and after inhalation of the following medications: CombiventÔ metered-dose inhaler (MDI) (CFC-containing); VentolinÔ MDI (CFC-free); AtroventÔ MDI (CFC-free), BeclazoneÔ MDI (CFC-containing); DuolinÔ nebuliser. In addition, the duration of the persistence of the mass/charge ratios was measured for 20,h. Inhalers containing CFCs generated large peaks at m/z 85, 87, 101, 103 and 105 in vitro and in vivo, consistent with the predicted product ions of CFCs 12, 114 and 11. No such peaks were seen with DuolinÔ via nebuliser, or CFC-free MDIs. We conclude that measurement of VCs, such as haloamines, with product ions of similar m/z values to the ions found for CFCs would be significantly affected by the presence of CFCs in inhalers. This issue needs to be accounted for prior to the measurement of VCs in breath in people using inhalers containing CFCs. Copyright © 2009 John Wiley & Sons, Ltd. [source] Rapid determination of three anticoagulant rodenticides in whole blood by liquid chromatography coupled with electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2006Mi-cong Jin A rapid, sensitive and selective method for the simultaneous determination of bromadiolone, flocoumafen and brodifacoum in whole blood using warfarin as internal standard (IS) by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC/ESI-MS) has been developed and validated. The target compounds were extracted from the whole blood with ethyl acetate and separated on an XDB C18 column (150,mm,×,2.1,mm i.d.,×,5,µm) by using a mobile phase consisting of 0.2% acetic acid/methanol (12/88, v/v) at a constant flow rate of 0.50 mL/min. The analytes were detected using negative ESI-MS in the selected ion monitoring (SIM) mode. The molecular ions [MH], of m/z 527, 541,523 and 307 were selected for the quantification for bromadiolone, flocoumafen, brodifacoum and the IS, respectively. The calibration curves were linear (r2,>,0.995) in the concentration range of 0.50,100.00 ng/mL. The method showed a satisfactory sensitivity (0.05,0.5 ng/mL using 200 µL blood), precision (RSD,<,11.9%), accuracy (recovery: 82.0,96.1%) and selectivity. This method was successfully applied to the determination of the analytes for the diagnoses of poisoned human beings and animals. Copyright © 2006 John Wiley & Sons, Ltd. [source] High-throughput determination of carbocysteine in human plasma by liquid chromatography/tandem mass spectrometry: application to a bioequivalence study of two formulations in healthy volunteersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2006Hui-chang Bi A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method to determine carbocysteine in human plasma was developed and fully validated. After methanol-induced protein precipitation of the plasma samples, carbocysteine was subjected to LC/MS/MS analysis using electrospray ionization (ESI). The MS system was operated in the selected ion monitoring (SRM) mode. Chromatographic separation was performed on a Hypurity C18 column (i.d. 2.1,mm,×,50,mm, particle size 5,µm). The method had a chromatographic running time of 2.0,min and linear calibration curves over the concentration ranges of 0.1,20,µg/mL for carbocysteine. The lower limit of quantification (LLOQ) of the method was 0.1,µg/mL for carbocysteine. The intra- and inter-day precision was less than 7% for all quality control samples at concentrations of 0.5, 2.0, and 10.0,µg/mL. These results indicate that the method was efficient with a simple preparation procedure and a very short running time (2.0,min) for carbocysteine compared with methods reported in the literature and had high selectivity, acceptable accuracy, precision and sensitivity. The validated LC/MS/MS method has been successfully used to a bioequivalence study of two tablet formulations of carbocysteine in healthy volunteers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous quantitative determination of cyclosporine A and its three main metabolites (AM1, AM4N and AM9) in human blood by liquid chromatography/mass spectrometry using a rapid sample processing methodRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2006Nozomu Koseki We have developed a sensitive and specific liquid chromatography/mass spectrometry (LC/MS) method for the simultaneous determination of cyclosporine A (CsA) and its three main metabolites (AM1, AM4N and AM9) in human blood. Following protein precipitation, supernatant was directly injected into the LC/MS system. Chromatographic separation was accomplished on a Symmetry C8 (4.6,×,75,mm, 3.5,µm) column with a linear gradient elution prior to detection by atmospheric pressure chemical ionization (APCI) MS using selected ion monitoring (SIM) in positive mode. This method can be applied to single mass equipment. The analytical range for each analyte was set at 1,2500,ng/mL using 100,µL of blood sample. The analytical method was fully validated according to FDA guidance. Intra-day mean accuracy and precision were 95.2,113.5% and 0.9,8.9%, respectively. Inter-day mean accuracy and precision were 95.8,107.0% and 1.5,10.7%, respectively. In blood all analytes were stable during three freeze/thaw cycles, for 24,h at room temperature and for 12 months at or below ,15°C. Stability was also confirmed in processed samples for 24,h at 10°C and for 6 months at 4°C in methanol. In addition, we confirmed the method could avoid matrix effects from transplant subjects' samples. This LC/MS technique provided an excellent method for simultaneous quantitative determination of CsA and its three metabolites for evaluation of their pharmacokinetic profiles. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous determination of ten antihistamine drugs in human plasma using pipette tip solid-phase extraction and gas chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006Chika Hasegawa Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18 -bonded monolithic silica gel was fixed. Human plasma (0.1,mL) containing the ten antihistamines was mixed with 0.4,mL of distilled water and 25,µL of a 1,M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30,m,×,0.32,mm i.d., film thickness 0.25,µm). The recoveries of the ten antihistamines spiked into plasma were 73.8,105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02,5.0,ng/0.1,mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented. Copyright © 2006 John Wiley & Sons, Ltd. [source] Direct determination of endogenous melatonin in human saliva by column-switching semi-microcolumn liquid chromatography/mass spectrometry with on-line analyte enrichmentRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2004Akira Motoyama An analytical method that enables direct and sensitive determination of endogenous melatonin (MLT) in human saliva was developed by means of column-switching semi-microcolumn liquid chromatography (i.d.: 1,2,mm)/mass spectrometry (LC/MS). The system allows direct injection analysis of a 400-,L aliquot of saliva with minimal sample pretreatment (internal standard (IS) addition and vortex mixing) and a relatively short run-time (10,min). The system consists of three columns to attain large volume injection and on-line analyte enrichment. A pre-column packed with a silica-based mixed-functional C8 (4.0,mm i.d.,×,20,mm) was used for on-line sample cleanup. MLT and an IS, the d7 isomer of MLT (d7-MLT), were heart-cut by valve switching and enriched at the top of the intermediate trapping column packed with a silica-based C18 (4.0,mm i.d.,×,10,mm). Subsequently, the analytes were backflushed into a semi-micro C18 silica column (2.0,mm i.d.,×,150 mm) for the final separation. MLT and IS were ascertained by positive electrospray ionization and selected ion monitoring (SIM). MLT was monitored based on its fragment ion at m/z 174.1 by in-source collision-induced dissociation (CID). The validation of this method revealed a detection limit of 2.5,pg,mL,1 at a signal-to-noise (S/N) ratio of 5. The linearity of the method was established in the ranges 5,250 and 100,2500,pg,mL,1 with a coefficient of determination of greater than 0.998. Accuracies, evaluated at five levels in the range 5,1000,pg,mL,1, were between 81 and 108% with a relative standard deviation (RSD) ranging from 1.3,20%. The method was successfully applied for the endogenous saliva MLT monitoring of two healthy subjects. Copyright © 2004 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] Analysis of bacterial lipodepsipeptides by matrix-assisted laser desorption/ionisation time-of-flight and high-performance liquid chromatography with electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2001Simona Maria Monti Strains of certain plant pathogenic bacteria, in particular several pathovars of Pseudomonas syringae, are known to produce cyclic lipodepsipeptides (LDPs) endowed with peculiar structural features and noticeable biological activities. In this study, a mass spectrometry procedure is proposed for screening LDP-producing bacterial strains and for identifying and assessing individual LDPs. After matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) screening of thirteen P. syringae strains for LDP production, the extracts from culture filtrates of eight positive strains were subjected to electrospray mass spectrometry for the identification of LDPs. Five strains were found to produce two forms of syringomycins (SR-E and SR-G) and two forms of syringopeptin 25 (SP25A and SP25B); two strains produced SR-E, SR-G and a new form of SP22; one strain produced syringotoxin (ST) and syringostatin A (SS-A) in addition to SP25A and SP25B. The yield in culture of two major LPDs: SR-G (3.2,13.8,mg L,1) and SP25A (41.6,231.5,mg L,1) was assessed by and high-performance liquid chromatography with electrospray mass spectrometry (HPLC/ESI-MS) in both scan and single ion monitoring (SIM) modes. Results of this investigation showed that the mass spectrometry protocol developed here is a precise and reliable method for screening bacterial strains for LDP production and for assessing the amount of each metabolite under various culture conditions. This could be of practical value in view of potential applications, e.g. biocontrol of post-harvest fungal diseases. Copyright © 2001 John Wiley & Sons, Ltd. [source] A rapid assay for angiotensin-converting enzyme activity using ultra-performance liquid chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 3 2010Fang Geng Abstract Angiotensin-converting enzyme (ACE) plays an important role in the renin,angiotensin system and ACE activity is usually assayed in vitro by monitoring the transformation from a substrate to the product catalyzed by ACE. A rapid and sensitive analysis method or ACE activity by quantifying simultaneously the substrate hippuryl,histidyl,leucine and its product hippuric acid using an ultra-performance liquid chromatography coupled with electrospray ionization-mass spectrometry (UPLC-MS) was first developed and applied to assay the inhibitory activities against ACE of several natural phenolic compounds. The established UPLC-MS method showed obvious advantages over the conventional HPLC analysis in shortened running time (3.5,min), lower limit of detection (5,pg) and limit of quantification (18,pg), and high selectivity aided by MS detection in selected ion monitoring (SIM) mode. Among the six natural products screened, five compounds, caffeic acid, caffeoyl acetate, ferulic acid, chlorogenic acid and resveratrol indicated potent in vitro ACE inhibitory activity with IC50 values of 2.527 ± 0.032, 3.129 ± 0.016, 10.898 ± 0.430, 15.076 ± 1.211 and 6.359 ± 0.086,mm, respectively. A structure,activity relationship estimation suggested that the number and the situation of the hydroxyls on the benzene rings and the acrylic acid groups may play the most predominant role in their ACE inhibitory activity. Copyright © 2009 John Wiley & Sons, Ltd. [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] Simultaneous clinical monitoring of lactic acid, pyruvic acid and ketone bodies in plasma as methoxime/tert-butyldimethylsilyl derivatives by gas chromatography,mass spectrometry in selected ion monitoring modeBIOMEDICAL CHROMATOGRAPHY, Issue 5 2008Man-Jeong Paik Abstract Simultaneous determination of lactic acid, pyruvic acid, 3-hydroxybutyric acid and acetoacetic acid for clinical monitoring of lactic acidosis and ketone body formation in human plasma (20 µL) was performed by gas chromatography,mass spectrometry in selected ion monitoring (SIM) mode after generating methoxime/tert-butyldimethylsilyl derivatives. All of the targeted carboxylic acids were detected by characteristic fragment ions, which permitted sensitive and selective identification in the presence of co-extracted free fatty acids and other acidic metabolites at much higher levels. The method was linear (r , 0.9991), reproducible (% relative standard deviation = 1.2,5.8), and accurate (% relative error = ,7.2,7.6), with detection limits of 0.05,1.7 ng/mL. This rapid, accurate and selective method using minimal plasma samples (20 µL) is useful in the clinical monitoring of lactic acidosis and ketone body formation in plasma. Copyright © 2008 John Wiley & Sons, Ltd. [source] Quantitative determination of alkylated quaternary amines and their n -hydroxylated metabolites in an enzyme incubation matrix by liquid chromatography electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 8 2005Victoria E. Holmes Abstract A simple, rapid and sensitive reversed-phase liquid chromatography method coupled to electrospray ionization mass spectrometry has been developed for studying the in vitro metabolism of the long-chain quaternary ammonium compounds dodecyltrimethylamine, tetradecyltrimethylamine and hexadecyltrimethylamine. Samples were prepared from the biological matrix by a simple protein precipitation stage. The separation was performed using a BDS Hypersil C8 3 µm particle size (100 × 3 mm i.d.) column with a fast gradient separation (60% B to 100% B) using a mobile phase of 10 mm aqueous ammonium acetate (pH 4.0, with 0.06% triethylamine; (A),acetonitrile (B) at 0.7 mL min,1. To minimize contamination of the MS source a switching value was used to divert the solvent front to waste. Decylammonium bromide was used as the internal standard and analytes were identified and quantified by positive ion electrospray selected ion monitoring of their intact molecular cations. The assay had a limit of quantitation of 0.25 µm (6.25 pmol on column) and was linear over the range 0.25,100 µm assay concentration for this series of long-chain quaternary amines. The precision of intra- and inter-day assays was better than 19% and the accuracy was between 93 and 109%. The method was used to assess the in vitro metabolism of the quaternary amines by wild-type cytochrome P450 enzyme CYP4A1 and mutants in an artifical membrane system. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||