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LC/MS/MS
Terms modified by LC/MS/MS Selected AbstractsAccelerating drug development: methodology to support first-in-man pharmacokinetic studies by the use of drug candidate microdosingDRUG DEVELOPMENT RESEARCH, Issue 1 2007Matthew A. McLean Abstract Microdosing of experimental therapeutics in humans offers a number of benefits to the drug development process. Microdosing, conducted under an exploratory Investigational New Drug (IND) application, entails administration of a sub-pharmacological dose of a new chemical entity (NCE) that allows for early evaluation of human pharmacokinetics. Such information can be pivotal for: (1) selecting a compound for full drug development from a small group of candidates; (2) defining the amount of material needed for early development; and (3) setting the initial Phase I dose regimen in humans. Appropriate safety studies must be conducted to support microdosing in humans, but the requirements are generally less extensive than those needed to support a traditional IND. To date, microdosing has not been broadly applied by the pharmaceutical industry due to concerns about analytical sensitivity and the possibility of non-linear pharmacokinetics at extremely low doses. The primary method for detecting analytes following microdosing until now has been accelerator mass spectrometry, which is expensive, not generally available, and requires test agents to be radiolabeled. Presented in this report is an example of pharmacokinetics analysis using LC/MS/MS following microdosing of an experimental agent in cynomolgus monkeys. The results show good linearity in plasma pharmacokinetics for oral doses of 10,mg/kg (therapeutic dose) and 0.0005,mg/kg (microdose) of the test agent. The results also demonstrate the feasibility of applying standard laboratory analytics to support microdosing in humans and raise the possibility of establishing an animal model to screen for compounds having non-linear pharmacokinetics at low dose levels. Drug Dev. Res. 68:14,22, 2007. © 2007 Wiley-Liss, Inc. [source] A new morphospecies of Microcystis sp. forming bloom in the Cheffia dam (Algeria): Seasonal variation of microcystin concentrations in raw water and their removal in a full-scale treatment plantENVIRONMENTAL TOXICOLOGY, Issue 4 2007Hichèm Nasri Abstract Toxic cyanobacterial blooms are an increasing problem in Algeria. The production of cyanotoxins (microcystins) and their presence in drinking water represent growing hazards to human health. In this study, seasonal variations in the concentrations of total microcystins and physicochemical parameters (pH, temperature, dissolved oxygen, nitrate, orthophosphate, and chlorophyll- a) were analyzed in the Cheffia dam (Algeria), mainly used to supply drinking water. The removal of cyanobacterial cells and microcystins was also evaluated in full-scale plant associated with the Cheffia reservoir. The levels of microcystins (MCYSTs) in both raw and drinking water were evaluated using the protein phosphatase type 2A (PP2A) inhibition test as MCYST-LR equivalents. Identification of microcystin variants was achieved by LC/MS/MS. During the period of study (March,December 2004), microscopic observation showed the dominance in the autumn months (September,November) of a new morphospecies of Microcystis sp. The MCYST-LR equivalent concentrations in raw water varied between 50.8 and 28,886 ng L,1. The highest level of toxins was observed in October 2004 and was significantly correlated with the chlorophyll- a. Three variants of microcystins assigned as microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR), and 6Z -Adda stereoisomer of MCYST-LR were observed in the crude extract of the Microcystis sp. bloom sample. During the bloom period, total elimination of Microcystis sp. and toxins were achieved through a classical treatment plant comprised of coagulation and flocculation, powdered activated carbon at 15 mg L,1, slow sand filtration and chlorination before storage. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 347,356, 2007. [source] Identification and characterization of a new gene from Variovorax paradoxus Iso1 encoding N -acyl- d -amino acid amidohydrolase responsible for d -amino acid productionFEBS JOURNAL, Issue 19 2002Pei-Hsun Lin An N -acyl- d -amino acid amidohydrolase (N -D-AAase) was identified in cell extracts of a strain, Iso1, isolated from an environment containing N -acetyl- d -methionine. The bacterium was classified as Variovorax paradoxus by phylogenetic analysis. The gene was cloned and sequenced. The gene consisted of a 1467-bp ORF encoding a polypeptide of 488 amino acids. The V. paradoxusN -D-AAase showed significant amino acid similarity to the N -acyl- d -amino acid amidohydrolases of the two eubacteria Alcaligenes xylosoxydans A-6 (44,56% identity), Alcaligenes facelis DA1 (54% identity) and the hyperthermophilic archaeon Pyrococcus abyssi (42% identity). After over-expression of the N -D-AAase protein in Escherichia coli, the enzyme was purified by multistep chromatography. The native molecular mass was 52.8 kDa, which agreed with the predicted molecular mass of 52 798 Da and the enzyme appeared to be a monomer protein by gel-filtration chromatography. A homogenous protein with a specific activity of 516 U·mg,1 was finally obtained. After peptide sequencing by LC/MS/MS, the results were in agreement with the deduced amino acid sequence of the N -D-AAase. The pI of the enzyme was 5.12 and it had an optimal pH and temperature of 7.5 and 50 °C, respectively. After 30 min heat treatment at 45 °C, between pH 6 and pH 8, 80% activity remained. The N -D-AAase had higher hydrolysing activity against N -acetyl- d -amino acid derivates containing d -methionine, d -leucine and d -alanine and against N -chloroacetyl- d -phenylalanine. Importantly, the enzyme does not act on the N -acetyl- l -amino acid derivatives. The enzyme was inhibited by chelating agents and certain metal ions, but was activated by 1 mm of Co2+ and Mg2+. Thus, the N -D-AAase from V. paradoxus can be considered a chiral specific and metal-dependent enzyme. [source] Use of liquid chromatography,tandem mass spectrometry for quantitative analysis of clopyralid in compost and forageGRASSLAND SCIENCE, Issue 3 2009Ryuichi Uegaki Abstract In this study, we first developed a technique to quantify clopyralid using liquid chromatography,tandem mass spectrometry (LC/MS/MS) and tested its performance for compost and corn plant samples. Then, we measured the uptake of clopyralid by forage corn grown on two types of soil mixed with clopyralid-contaminated compost, in order to investigate the potential of ingestion of compost clopyralid by animals through forage crops. Because of the high recovery ratios (80,82% for compost and 98% for corn), sufficient theoretical quantification limits (5.0 and 1.7 ,g kg,1 fresh matter, respectively) and close agreement with the bioassay method (73 ,g kg,1 for LC/MS/MS and 80 ,g kg,1 for bioassay), the LC/MS/MS method was considered to be of potential value for determining clopyralid in compost and plant materials. Corn plants took up clopyralid from soil (compost), with the amount and rate of uptake varying with soil types and application of activated carbon to soil. There is a need for quantifying clopyralid uptake by a range of forage crops under a range of cultivation conditions (e.g. climate, soil, management) to estimate clopyralid fluxes through the manure,forage,animal,manure pathway. [source] Rapid screening assay of congenital adrenal hyperplasia by measuring 17,-hydroxyprogesterone with high-performance liquid chromatography/electrospray ionization tandem mass spectrometry from dried blood spotsJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 1 2002Chien-Chen Lai Abstract A rapid, simple, and specific method was developed for the diagnosis of congenital adrenal hyperplasia (CAH) from dried blood spots on newborn screening cards based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS). The usefulness of 17,-hydroxyprogesterone (17OH-P) determination on dried filter-paper blood samples from patients with CAH caused by 21-hydroxylase deficiency was evaluated. The LC/MS/MS detection of 17OH-P was rapid, <4 min. The intra- and interday accuracy and precision of the method were <7%. Our procedure maintained good linearities (R2 > 0.992) and recovery rate (>83%). We used this new method to directly determine the 17OH-P levels in dried blood specimens from abnormal children of various ages, with a detection limit of 20 ng/ml (,240 pg), to avoid the time-consuming derivatization steps required by the gas-chromatography/mass spectrometry (GC/MS) method. Four dried filter-paper blood samples of CAH patients (three girls and one boy, 1,14 years old) were all quantified in an LC/MS/MS study and revealed high 17OH-P levels (>90 ng/ml). After treatment, all of the elevated 17OH-P levels either decreased or disappeared. Compared with CAH patients, 17OH-P was nearly undetectable (<20 ng/ml) in the normal infants by LC/MS/MS. This LC/MS/MS assay is not only useful for both diagnosis and monitoring of treatment of CAH in all other age groups, it also can be used as a screening test for CAH infants. In this study, we provided the first data on 17OH-P in dried blood specimens affected with CAH using HPLC/ESI-MS/MS. J. Clin. Lab. Anal. 16:20,25, 2002. © 2002 Wiley-Liss, Inc. [source] Detection of Acute Diazepam Exposure in Bone and Marrow: Influence of Tissue Type and the Dose-Death Interval on Sensitivity of Detection by ELISA with Liquid Chromatography Tandem Mass Spectrometry Confirmation,JOURNAL OF FORENSIC SCIENCES, Issue 3 2009D.A.B.F.T., James H. Watterson Ph.D. Abstract:, Enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC/MS/MS) were used to detect diazepam exposure in skeletal tissues of rats (n = 15) given diazepam acutely (20 mg/kg, i.p.), and killed at various times postdose. Marrow, epiphyseal, and diaphyseal bone were isolated from extracted femora. Bone was cleaned, ground, and incubated in methanol. Marrow underwent ultrasonic homogenization. Extracts and homogenates were diluted in phosphate buffer, and then underwent solid-phase extraction and ELISA. Relative sensitivity of detection was examined in terms of relative decrease in absorbance (ELISA) and binary classification sensitivity (ELISA and LC/MS/MS). Overall, the data showed differences in relative sensitivity of detection of diazepam exposure in different tissue types (marrow > epiphyseal bone > diaphyseal bone), which is suggestive of heterogenous distribution in these tissues, and a decreasing sensitivity with increasing dose-death interval. Thus, the tissue type sampled and dose-death interval may contribute to the probability of detection of diazepam exposure in skeletal tissues. [source] Relationships Between Concentrations of Cocaine and Its Hydrolysates in Peripheral Blood, Heart Blood, Vitreous Humor and UrineJOURNAL OF FORENSIC SCIENCES, Issue 2 2006Wayne C. Duer Ph.D. ABSTRACT: Cocaine is known to degrade in vivo and in vitro by several hydrolytic mechanisms. A previous study found that the initial amount of cocaine added to plasma could be accounted for by summing the molar concentrations of cocaine's hydrolysis products and the cocaine remaining after hydrolysis. The present study was undertaken to investigate whether or not relationships might exist between such molar concentration sums for different postmortem bodily fluids. Determinations of cocaine, benzoylecgonine, ecgonine methyl ester, and ecgonine were performed using liquid chromatography/mass spectrometry (LC/MS/MS) with heart blood, femoral blood, vitreous humor (VH), and urine (UR). The results demonstrate a strong correlation between blood and VH concentrations (correlation coefficients of 0.88,0.94), weak correlation between the UR and blood concentrations (correlation coefficients of 0.61,0.64), and weak correlation between UR and VH concentrations (correlation coefficient of 0.59). The results demonstrate that ecgonine is a significant hydrolysate with concentrations on the same order of magnitude as benzoylecgonine. The results are consistent with rapid distribution of the parent drug and its hydrolysates in the blood and VH. The strong correlation between the blood and VH demonstrates that VH is an important medium for toxicology testing when attempting to make a determination of cocaine intoxication. [source] Combination of liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry for the detection of 21 anabolic steroid residues in bovine urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2005Christof Van Poucke Abstract For the detection of anabolic steroid residues in bovine urine, a highly sensitive liquid chromatographic/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method was developed using both positive and negative ionization. For four compounds the ESI mode was not sensitive enough and gas chromatographic/mass spectrometric GC/MS detection was therefore still necessary as a complementary method. The sample clean-up consisted of solid-phase extraction (SPE) on a C18 column followed by enzymatic hydrolysis and a second solid-phase extraction on a combination of a C18 and a NH2 column. After this last SPE clean-up, the eluate was split into two equal aliquots. One aliquot was further purified and after derivatization used for GC/MS analysis. The other aliquot was analyzed with LC/MS/MS in both ESI+ and ESI, modes. The method was validated according to the European Commission Decision 2002/657/EC. Decision limits (CC,) were between 0.16 and 1 ng ml,1 for the compounds detected with the LC/MS/MS method. The developed method is used in routine analysis in our laboratory. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantitative analysis of the P-glycoprotein inhibitor Elacridar (GF120918) in human and dog plasma using liquid chromatography with tandem mass spectrometric detectionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004Ellen Stokvis Abstract A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method for the determination of the P-glycoprotein and breast cancer resistance protein inhibitor Elacridar in human and dog plasma is described. The internal standard was stable isotopically labelled Elacridar. Sample pretreatment involved liquid,liquid extraction with tert -butyl methyl ether. Analysis of Elacridar and internal standard was performed by reversed-phase LC on a basic stable minibore analytical column with an eluent consisting of acetonitrile and aqueous ammonia. An API-2000 triple-quadrupole mass spectrometer with an electrospray ion source was used in the positive-ion multiple reaction monitoring mode. The run time per sample was only 6 min. The method is sensitive and specific, with a dynamic range from 1 to 500 ng ml,1 from 100 µl of human or dog plasma. The accuracy of the method was within 15% bias and the precision was lower than 15% for all tested concentration levels and in both matrices. The method is simple and the liquid,liquid extraction produces clean samples. This method was successfully applied to support the pharmacokinetics of a clinical trial in which orally applied Elacridar was used as a bioavailability enhancer. Copyright © 2004 John Wiley & Sons, Ltd. [source] Simultaneous quantification of cyclophosphamide, 4-hydroxycyclophosphamide, N,N,,N, -triethylenethiophosphoramide (thiotepa) and N,N,,N, -triethylenephosphoramide (tepa) in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2004Milly E. de Jonge Abstract The alkylating agents cyclophosphamide (CP) and N, N,, N, -triethylenethiophosphoramide (thiotepa) are often co-administered in high-dose chemotherapy regimens. Since these regimens can be complicated by the occurrence of severe and sometimes life-threatening toxicities, pharmacokinetically guided administration of these compounds, to reduce variability in exposure, may lead to improved tolerability. For rapid dose adaptations during a chemotherapy course, we have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of CP, thiotepa and their respective active metabolites 4-hydroxycyclophosphamide (4OHCP) and N, N,, N, -triethylenephosphoramide (tepa) in plasma. Because of the instability of 4OHCP in plasma, the compound is derivatized with semicarbazide (SCZ) immediately after sample collection and quantified as 4OHCP-SCZ. Sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using 100 µl of plasma. Chromatographic separation was performed on an Zorbax Extend C18 column (150 × 2.1 mm i.d., particle size 5 µm), with a quick gradient using 1 mM ammonia solution and acetonitrile, at a flow-rate of 0.4 ml min,1. The analytical run time was 10 min. The triple quadrupole mass spectrometer was operating in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 200,40 000 ng ml,1 for CP, 50,5000 ng ml,1 for 4OHCP-SCZ and 5,2500 ng ml,1 for thiotepa and tepa, using 100 µl of human plasma. These dynamic concentration ranges proved to be relevant in daily practice. Hexamethylphosphoramide was used as an internal standard. The coefficients of variation were <12% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (±15%). This robust and rapid LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring of CP, thiotepa and their metabolites in our hospital. Copyright © 2004 John Wiley & Sons, Ltd. [source] Qualitative study of in vivo melphalan adduct formation in the rat by miniaturized column-switching liquid chromatography coupled with electrospray mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2004Bart Van den Driessche Abstract In a general study of DNA adduct formation with melphalan, rats were intravenously injected with a single high dose (10 mg kg,1). Adduct formation was studied at the nucleoside level in the target organs liver, bone marrow, kidney and blood with the use of 2D liquid chromatography/tandem mass spectrometry (LC/MS/MS). Adducts of dGuo and dAdo were detected under selected reaction monitoring in liver and bone marrow 10 h after administration of melphalan. In the DNA hydrolysates from kidney and blood a Gua,melphalan adduct was found, although in very low abundance. These first results of the search for in vivo -formed melphalan adducts in the rat showed that our miniaturized LC/MS technique is useful for investigating this type of compound. More experiments will be performed in this area to gather more information about the pharmacokinetics and the quantity of adducts formed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Modulation of Brain Endocannabinoid Levels by Voluntary Alcohol Consumption in Alcohol-Preferring AA RatsALCOHOLISM, Issue 10 2009Hanna Malinen Background:, The central nervous system cannabinoid CB1 receptors have been implicated in regulation of alcohol consumption. Less data are available on the role of the endogenous ligands for these receptors, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), in alcohol-related behaviors. The purpose of this study was to assess the effects of voluntary alcohol consumption on the levels of these endocannabinoids in key brain areas mediating alcohol reinforcement. Methods:, Female and male alcohol-preferring AA (Alko, Alcohol) rats were trained to drink 10% (v/v) alcohol during 90-min limited access sessions every second day. Following establishment of stable alcohol drinking, half of the subjects were killed immediately before the daily alcohol access ("pre-session" group), while the other half was killed after the drinking session ("post-session" group). A separate control group consisted of water-drinking rats. AEA and 2-AG levels were measured from prefrontal cortex (PFC), nucleus accumbens (NAc), caudate putamen (CPu), amygdala, and hippocampus using liquid chromatography,tandem mass spectrometry (LC/MS/MS). Results:, Voluntary alcohol drinking caused widespread alterations in the levels of both AEA and 2-AG. Compared to the water group, increased AEA levels were seen in the pre-session group, but they were decreased immediately following limited access drinking in the female AA rats. Also 2-AG levels were significantly elevated after long alcohol exposure, and an additional increase was found after limited access drinking in PFC. In males, however, the only alterations caused by alcohol drinking were significantly elevated AEA levels in NAc and CPu in the post-session group. No changes were seen in the levels of 2-AG. Conclusions:, These results demonstrate that voluntary alcohol drinking modulates the levels of endocannabinoids in several brain areas implicated in alcohol reinforcement. AEA and 2-AG were differentially affected, suggesting that they could have partially separate modulatory roles. Alterations were more widespread in females than males, possibly reflecting their higher alcohol intake. Taken together, alcohol-induced release of endocannabinoids may have an important role in alcohol reinforcement and development of alcohol addiction. [source] Extensive fractionation and identification of proteins within nasal lavage fluids from allergic rhinitis and asthmatic chronic rhinosinusitis patientsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Linda M. Benson Abstract Allergic rhinitis (AR), chronic rhinosinusitis (CRS), and asthma are prevalent airway diseases that can have a substantial impact on a patient's quality of life. MS analyses of biological fluids can effectively screen for proteins associated with disease processes, however, initial detection of diagnostic proteins is difficult due to protein complexity and dynamic range. To enhance the detection of lower abundance proteins, intact nasal lavage fluid (NLF) proteins from nonpolypoid AR and from asthmatic CRS patients were extensively fractionated prior to LC/MS/MS analysis. Pooled NLF samples were processed to remove low molecular weight molecules and high abundance plasma proteins. Anion exchange (AX) chromatography followed by RP-LC further separated the remaining intact NLF proteins. The resulting fractions were digested with trypsin and the peptides analyzed by LC/MS/MS. Spectra were searched with MASCOT, SEQUEST, and X!Tandem to obtain peptide identifications and subsequently analyzed by Scaffold software to identify parent proteins with at least 99% confidence. The 197 identified proteins are compared to those previously cited in the literature and the workflow evaluated to determine the usefulness for the detection of lower abundance proteins. This is the first extensive list of NLF proteins generated from CRS patients with coexisting asthma. [source] Identification of desulphoglucosinolates in Brassicaceae by LC/MS/MS: Comparison of ESI and atmospheric pressure chemical ionisation-MSMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 12 2007Nadine S. Zimmermann Abstract In order to develop a sensitive method for the detection of desulphoglucosinolates by HPLC-MS, the two most common interfaces for HPLC-MS, atmospheric pressure chemical ionisation (APCI) and ESI, were compared. While working with the APCI-interface the evaporation temperature and corona amperage were optimised. In doing so 300°C and 6 ,A proved to be most suitable for aliphatic and indole desulphoglucosinolates. The use of formic acid instead of water in the eluent in HPLC-ESI-MS measurements increased the sensitivity for the indole desulphoglucosinolates in the presence of 1 mM formic acid, while the sensitivity for the aliphatic desulphoglucosinolate desulphoglucoraphanin was substantially increased by the presence of 5 mM formic acid. Using an Agilent ion trap, two optimisation procedures for the MS parameters, smart and expert mode, were available. In smart mode the software optimises several parameters automatically, which is much more time efficient than expert mode, in which the optimisation is done manually. It turned out that ESI-MS is most sensitive in smart mode, while for APCI-MS a higher sensitivity could be gained using the expert mode. Comparing both interfaces, APCI-MS was more sensitive than ESI-MS. However, no additional information, in terms of structure determination, was obtained by APCI-MS. [source] Effects of salinity levels on proteome of Suaeda aegyptiaca leavesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2006Hossein Askari Abstract Saline soils are the major problem of cultivated lands of Iran. Suaeda aegyptiaca is a salt-tolerant plant (halophytes) that grow naturally in salt-affected areas of Iran. We have employed proteomics to identify the mechanisms of salt responsiveness in leaves of S.,aegyptiaca grown under different salt concentrations. Ten-day-old plants were treated with 0, 150, 300, 450, and 600,mM NaCl. After 30,days of treatment, leaf samples were collected and analyzed using 2-D-PAGE. Out of 700,protein spots reproducible detected within replications, 102,spots showed significant response to salt treatment compared to 0,mM,NaCl. We analyzed expression pattern of salt-responsive proteins using a hierarchical and two nonhierarchical (Fuzzy ART and SOM) statistical methods and concluded that Fuzzy ART is the superior method. Forty proteins of 12,different expression groups were analyzed using LC/MS/MS. Of these, 27,protein spots were identified including proteins involved in oxidative stress tolerance, glycinebetain synthesis, cytoskeleton remodeling, photosynthesis, ATP production, protein degradation, cyanide detoxification, and chaperone activities. The expression pattern of these proteins and their possible roles in the adaptation of S.,aegyptiaca to salinity is discussed. [source] Development of a targeted adductomic method for the determination of polycyclic aromatic hydrocarbon DNA adducts using online column-switching liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2010Rajinder Singh Human exposure to polycyclic aromatic hydrocarbons (PAHs) from sources such as industrial or urban air pollution, tobacco smoke and cooked food is not confined to a single compound, but instead to mixtures of different PAHs. The interaction of different PAHs may lead to additive, synergistic or antagonistic effects in terms of DNA adduct formation and carcinogenic activity resulting from changes in metabolic activation to reactive intermediates and DNA repair. The development of a targeted DNA adductomic approach using liquid chromatography/tandem mass spectrometry (LC/MS/MS) incorporating software-based peak picking and integration for the assessment of exposure to mixtures of PAHs is described. For method development PAH-modified DNA samples were obtained by reaction of the anti- dihydrodiol epoxide metabolites of benzo[a]pyrene, benzo[b]fluoranthene, dibenzo[a,l]pyrene (DB[a,l]P) and dibenz[a,h]anthracene with calf thymus DNA in vitro and enzymatically hydrolysed to 2,-deoxynucleosides. Positive LC/electrospray ionisation (ESI)-MS/MS collision-induced dissociation product ion spectra data showed that the majority of adducts displayed a common fragmentation for the neutral loss of 116 u (2,-deoxyribose) resulting in a major product ion derived from the adducted base. The exception was the DB[a,l]P dihydrodiol epoxide adduct of 2,-deoxyadenosine which resulted in major product ions derived from the PAH moiety being detected. Specific detection of mixtures of PAH-adducted 2,-deoxynucleosides was achieved using online column-switching LC/MS/MS in conjunction with selected reaction monitoring (SRM) of the [M+H]+ to [M+H,116]+ transition plus product ions derived from the PAH moiety for improved sensitivity of detection and a comparison was made to detection by constant neutral loss scanning. In conclusion, different PAH DNA adducts were detected by employing SRM [M+H,116]+ transitions or constant neutral loss scanning. However, for improved sensitivity of detection optimised SRM transitions relating to the PAH moiety product ions are required for certain PAH DNA adducts for the development of targeted DNA adductomic methods. Copyright © 2010 John Wiley & Sons, Ltd. [source] Comparison of analytical approaches for liquid chromatography/mass spectrometry determination of the alcohol biomarker ethyl glucuronide in urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2010Anders Helander Official guidelines originating from a European Union directive regulate requirements for analytical methods used to identify chemical compounds in biological matrices. This study compared different liquid chromatography/electropray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (LC/ESI-MS/MS) procedures for accurate determination of the conjugated ethanol metabolite and alcohol biomarker ethyl glucuronide (EtG) in urine, and the value of combined EtG and ethyl sulfate (EtS) measurement. Analysis was carried out on 482 urines following solid-phase extraction (SPE) sample cleanup or using direct injection of a diluted sample. SPE combined with LC/MS/MS was demonstrated to be the most selective and sensitive method and was chosen as reference method. The EtG results by different methods showed good correlation (r,=,0.96,0.98). When comparing five reporting limits for EtG in the range 0.10,1.00,mg/L, the overall agreement with the reference method (frequency of true positives plus true negatives) was 82,97% for direct-injection LC/MS/MS, 90,97% for SPE-LC/MS, 86,98% for direct-injection LC/MS, and 86,98% for direct-injection LC/MS analysis of EtG and EtS. Most deviations were attributable to uncertainty in quantitation, when the value was close to a cutoff but the respective results were slightly above and below, or vice versa, the critical limit. However, for direct-injection LC/MS/MS, despite earning 4 identification points, equally many negative results were due to a product ion ratio outside the ±20% deviation accepted by the guidelines. These results indicate that the likelihood of different analytical methods to provide reliable analytical results depends on the reporting limit applied. Copyright © 2010 John Wiley & Sons, Ltd. [source] Direct quantification of 11-nor-,9 -tetrahydrocannabinol-9-carboxylic acid in urine by liquid chromatography/tandem mass spectrometry in relation to doping control analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2010C. Chebbah An accurate and precise method for the quantification of 11-nor-,9 -tetrahydrocannabinol-9-carboxylic acid (THCA) in urine by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for doping analysis purposes has been developed. The method involves the use of only 200,µL of urine and the use of D9 -THCA as internal standard. No extraction procedure is used. The urine samples are hydrolysed using sodium hydroxide and diluted with a mixture of methanol/glacial acetic acid (1:1). Chromatographic separation is achieved using a C8 column with gradient elution. All MS and MS/MS parameters were optimised in both positive and negative electrospray ionisation modes. For the identification and the quantification of THCA three product ions are monitored in both ionisation modes. The method is linear over the studied range (5,40,ng/mL), with satisfactory intra-and inter-assay precision, and the relative standard deviations (RSDs) are lower than 15%. Good accuracy is achieved with bias less than 10% at all levels tested. No significant matrix effects are observed. The selectivity and specificity are satisfactory, and no interferences are detected. The LC/MS/MS method was applied for the analysis of 48 real urine samples previously analysed with a routine gas chromatography/mass spectrometry (GC/MS) method. A good correlation between the two methods was obtained (r2,>,0.98) with a slope close to 1. Copyright © 2010 John Wiley & Sons, Ltd. [source] Systematic investigation of ion suppression and enhancement effects of fourteen stable-isotope-labeled internal standards by their native analogues using atmospheric-pressure chemical ionization and electrospray ionization and the relevance for multi-analyte liquid chromatographic/mass spectrometric proceduresRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2010Daniela Remane In clinical and forensic toxicology, multi-analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi-analyte procedures, often only a limited number of stable-isotope-labeled internal standards (SIL-ISs) are available. If an SIL-IS is used for quantification of other analytes, it must be excluded that the co-eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL-ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric-pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL-ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix-based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL-ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. Copyright © 2010 John Wiley & Sons, Ltd. [source] Identification of circulatory and excretory metabolites of meisoindigo in rat plasma, urine and feces by high-performance liquid chromatography coupled with positive electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2010Meng Huang Meisoindigo has been a routine therapeutic agent in the clinical treatment of chronic myelogenous leukemia in China since the 1980s. However, information relevant to in vivo metabolism of meisoindigo is absent so far. In this study, in vivo circulatory metabolites of meisoindigo in rat plasma, as well as excretory metabolites in rat urine and feces, were identified by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Integration of multiple reaction monitoring with conventional metabolic profiling methodology was adopted to enable a more sensitive detection of in vivo metabolites. By comparing with the MS/MS spectra and retention times of the in vitro reduced metabolites, the major metabolites in rat plasma were proposed to form from 3,3, double bond reduction, whereas the minor metabolites were formed from reduction followed by N-demethylation, and reduction followed by phenyl mono-oxidation. The major metabolites in the rat urine were proposed to form from reduction followed by phenyl mono-oxidation, and its glucuronide conjugation and sulfate conjugation, whereas the minor metabolites were formed from 3,3, double bond reduction, N-demethylation, reduction followed by N-demethylation, phenyl di-oxidation, phenyl mono-oxidation and its glucuronide conjugation and sulfate conjugation. The major metabolites in the rat feces were proposed to form from reduction followed by phenyl mono-oxidation, whereas the minor metabolites were formed from reduction followed by N-demethylation, and reduction followed by phenyl di-oxidation. The phase I metabolic pathways showed a significant in vitro,in vivo correlation in rat. Copyright © 2010 John Wiley & Sons, Ltd. [source] Rapid screening and confirmation of drugs and toxic compounds in biological specimens using liquid chromatography/ion trap tandem mass spectrometry and automated library searchRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2010Hsiu-Chuan Liu Recent advances in liquid chromatography/tandem mass spectrometry (LC/MS/MS) technology have provided an opportunity for the development of more specific approaches to achieve the ,screen' and ,confirmation' goals in a single analytical step. For this purpose, this study adapts the electrospray ionization ion trap LC/MS/MS instrumentation (LC/ESI-MS/MS) for the screening and confirmation of over 800 drugs and toxic compounds in biological specimens. Liquid-liquid and solid-phase extraction protocols were coupled to LC/ESI-MS/MS using a 1.8-µm particle size analytical column operated at 50°C. Gradient elution of the analytes was conducted using a solvent system composed of methanol and water containing 0.1% formic acid. Positive-ion ESI-MS/MS spectra and retention times for each of the 800 drugs and toxic compounds were first established using 1,10,µg/mL standard solutions. This spectra and retention time information was then transferred to the library and searched by the identification algorithm for the confirmation of compounds found in test specimens , based on retention time matches and scores of fit, reverse fit, and purity resulting from the searching process. The established method was found highly effective when applied to the analyses of postmortem specimens (blood, urine, and hair) and external proficiency test samples provided by the College of American Pathology (CAP). The development of this approach has significantly improved the efficiency of our routine laboratory operation that was based on a two-step (immunoassay and GC/MS) approach in the past. Copyright © 2009 John Wiley & Sons, Ltd. [source] Characterization of tanshinones with quinone reductase induction activity from Radix Salvia miltiorrhiza by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2009Zhongjun Ma Quinone reductase (QR) induction is a reliable biomarker of phase II enzyme induction. In this study, glutathione (GSH) was employed and a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was introduced to reveal the chemical constituents with QR activity from the ethyl acetate extract of roots Salvia miltiorrhiza (,Danshen') and nine tanshinones (9, 13, 17-19, 21, 24,26), which could conjugate with GSH, were characterized by LC/MS/MS and considered to have QR activities. Then, thirteen tanshinones, including six compounds (17, 18, 21, 24,26) of the above nine tanshinones, were isolated to conduct QR induction evaluation, and it was found that miltirone and its derivatives (18, 20, 24, 26) exhibited significant activities. The GSH conjugate abilities of the isolated tanshinones were also examined; this showed that compounds 18, 20, 24 and 26 had good conjugating abilities with GSH. Compared with the in vitro bioactivity screening results, this proved that conjugate ability is related with QR activity, so an LC/MS/MS method can be applied to find more active compounds. Copyright © 2009 John Wiley & Sons, Ltd. [source] Phospholipids in liquid chromatography/mass spectrometry bioanalysis: comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effectsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2009Yuan-Qing Xia Because plasma phospholipids may cause matrix effects in bioanalytical liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods, it is important to establish optimal mass spectrometric techniques to monitor the fate of phospholipids during method development and application. We evaluated three MS/MS techniques to monitor phospholipids using positive and negative electrospray ionization (ESI). The first technique is based on using positive precursor ion scan of m/z 184, positive neutral loss scan of 141 Da and negative precursor ion scan of m/z 153. The second technique is based on using class-specific positive and negative selected reaction monitoring (SRM) transitions to monitor class-representative phospholipids. The third technique, previously reported, utilizes in-source collision-induced dissociation (CID)-based positive SRM of m/z 184,,,184. We recommend the all-inclusive technique 1 for use in qualitative assessment of all classes of phospholipids and technique 2 for use in quantitative assessment of class-representative phospholipids. Secondly, we evaluated the elution behaviors of the plasma phospholipids under different reversed-phase mobile phase conditions. The phospholipid-eluting strength of a mobile phase was mainly dependent on the type and amount (%) of the organic eluent and the strength increased in the order of methanol, acetonitrile and isopropyl alcohol. Under the commonly used gradient and isocratic elution schemes in LC/MS/MS bioanalysis, not all the phospholipids are eluted off the column. Thirdly, we investigated the association between phospholipids and matrix effects in positive and negative ESI using basic, acidic and neutral analytes. While the phospholipids caused matrix effects in both positive and negative ESI, the extent of ionization suppression was analyte-dependent and was inversely related to the retention factor and broadness of the phospholipids peaks. The lysophospholipids which normally elute earlier in reversed-phase chromatography are more likely to cause matrix effects compared to the later-eluting phospholipids in spite of the larger concentrations of the latter in plasma. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination of parabens, triclosan and triclocarban in water by liquid chromatography/electrospray ionisation tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2009Iria González-Mariño A method for the determination of several household biocides in water by liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) is presented. It permits the simultaneous determination of triclosan (TCS), triclocarban (TCC) and seven parabens, including the distinction between branched and linear isomers of propyl (i -PrP and n -PrP) and butyl parabens (i -BuP and n -BuP). Prior to LC/MS/MS, analytes are preconcentrated by solid-phase extraction (SPE) on Oasis HLB (60,mg) cartridges at natural sample pH and subsequently eluted with 4,mL of methanol. This simple SPE procedure provides extraction recoveries above 85% except for raw wastewater, where it falls to 65% for TCC. The performance of the method was tested with two triple-quadrupole LC/MS instruments from a low/mid and mid/high market range: a Varian 1200L and an API-4000. The latter system provided between 3 and 80 times lower limits of quantification (LOQs) than the first one, in the 0.08,0.44,ng/L range for surface water. Moreover, a comparison of matrix effects on both instruments showed a very different behaviour, particularly in the case of parabens. For these compounds signal suppression was observed in the 1200L instrument and signal enhancement with the 4000 instrument. As a result, different calibration approaches were chosen for them and this pointed to the need of matrix effect re-evaluation in method transfer between different LC/MS systems. The application of the method to real samples showed the ubiquity of methyl paraben (MeP) and n -PrP (at the 1,6,µg/L in raw wastewater) and the coexistence of i -BuP and n -BuP at similar levels (ca. 100,200,ng/L in raw wastewater). Copyright © 2009 John Wiley & Sons, Ltd. [source] False-positive liquid chromatography/tandem mass spectrometric confirmation of sebuthylazine residues using the identification points system according to EU directive 2002/657/EC due to a biogenic insecticide in tarragonRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Andreas Schürmann In pesticide residue analysis using liquid chromatography/tandem mass spectrometry (LC/MS/MS) the confirmation of a sebuthylazine finding in a tarragon (Artemisia dranunculus) sample was demonstrated to be false positive. A coeluting interfering matrix compound produced product ions in MS/MS analysis, perfectly corresponding to the multiple reaction monitoring (MRM) of two sebuthylazine transitions. Using the EU directive 2002/657/EC which regulates the confirmation of suspected positive findings would have resulted in a false-positive finding. A third LC/MS/MS transition with a deviant ion ratio and a gas chromatography (GC)/MS/MS analysis revealed the false-positive results. With optimized high resolving ultra-performance liquid chromatography (UPLC) conditions it was possible to separate spiked sebuthylazine from the interfering matrix compound. Using its exact mass and isotope ratios from LC/time-of-flight (TOF) MS measurements, the compound was identified as nepellitorine, a , not surprising , endogenous alkamide in tarragon (Arthemisia dranunculus). False-positive results, especially in heavy matrix samples such as herbs, can be dealt with by further confirmatory analysis, e.g. a third transition, GC analysis if possible or more advantageous by an orthogonal criterion like exact mass. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination of morphine, codeine, 6-acetylmorphine, cocaine and benzoylecgonine in hair by liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2009Da-Kong Huang A fast and sensitive liquid chromatography/triple quadrupole tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous determination of morphine, codeine, 6-acetylmorphine (6-AM), cocaine and benzoylecgonine (BE) in hair. Pulverized hair samples were extracted with methanol, and a 50,µL supernatant aliquot was injected into the LC/MS/MS system. Chromatography was performed with an XBridgeÔ phenyl column (3.5,µm particle size, 4.6,×,150,mm), and the mobile phase was composed of methanol and 10,mM ammonium acetate adjusted to pH 4.00 with 99% formic acid (95:5, v/v). A separation run with isocratic elution was completed in 10,min at a flow rate of 500,µL/min. Positive electrospray ionization and multiple reaction monitoring (MRM) with one precursor ion/product ion transition were used for the identification of each analyte. Deuterated analogues as internal standards were used for quantification and qualification. Linearity was established in the concentration range of 100,3000,pg/mg. The limits of detection were 10,pg/mg for morphine, codeine and 6-AM; and 1,pg/mg for cocaine and BE. The precision and accuracy were determined by spiking hair samples at six concentration levels. For all analytes, the relative standard deviations of intra- and inter-day precision were 0.1,6.3% and 1.5,10.6%, respectively. The accuracy ranged from 92.7 to 109.7%. The validated LC/MS/MS method was successfully applied to the analysis of 79 authentic hair samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Rapid detection and characterization of reactive drug metabolites in vitro using several isotope-labeled trapping agents and ultra-performance liquid chromatography/time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2009Timo Rousu Reactive metabolites are believed to be one of the main reasons for unexpected drug-induced toxicity issues, by forming covalent adducts with cell proteins or DNA. Due to their high reactivity and short lifespan they are not directly detected by traditional analytical methods, but are most traditionally analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) after chemical trapping with nucleophilic agents such as glutathione. Here, a simple but very efficient assay was built up for screening reactive drug metabolites, utilizing stable isotope labeled glutathione, potassium cyanide and semicarbazide as trapping agents and highly sensitive ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS) as an analytical tool. A group of twelve structurally different compounds was used as a test set, and a large number of trapped metabolites were detected for most of them, including many conjugates not reported previously. Glutathione-trapped metabolites were detected for nine of the twelve test compounds, whereas cyanide-trapped metabolites were found for eight and semicarbazide-trapped for three test compounds. The high mass accuracy of TOFMS provided unambiguous identification of change in molecular formula by formation of a reactive metabolite. In addition, use of a mass defect filter was found to be a usable tool when mining the trapped conjugates from the acquired data. The approach was shown to provide superior detection sensitivity in comparison to traditional methods based on neutral loss or precursor ion scanning with a triple quadrupole mass spectrometer, and clearly more efficient detection and characterization of reactive drug metabolites with a simpler test setup. Copyright © 2009 John Wiley & Sons, Ltd. [source] A liquid chromatography/tandem mass spectrometry method for detecting UGT-mediated bioactivation of drugs as their N -acetylcysteine adducts in human liver microsomesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2009Hiroshi Harada The detection of the reactive metabolites of drugs has recently been gaining increasing importance. In vitro trapping studies using trapping agents such as glutathione are usually conducted for the detection of reactive metabolites, especially those of cytochrome P450-mediated metabolism. In order to detect the UDP-glucuronosyltransferase (UGT)-mediated bioactivation of drugs, an invitro trapping method using N -acetylcysteine (NAC) as a trapping agent followed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed in this study. After the test compounds (diclofenac and ketoprofen) had been incubated in human liver microsomes with uridine diphosphoglucuronic acid (UDPGA) and NAC, the NAC adducts formed through their acyl glucuronides were analyzed using LC/MS/MS with electrospray ionization (ESI). The NAC adduct showed a mass shift of 145 units as compared to its parent, and the characteristic ion fragmentations reflected the parent. This is a concise and high-throughput method for evaluating reactive metabolites by UGT-mediated bioactivation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development of a multi-mycotoxin liquid chromatography/tandem mass spectrometry method for sweet pepper analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2009Sofie Monbaliu A multi-mycotoxin method was developed for the simultaneous determination of trichothecenes (nivalenol, deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, neosolaniol, fusarenon-X, diacetoxyscirpenol, HT-2 toxin, T-2 toxin), aflatoxins (aflatoxin-B1, aflatoxin-B2, aflatoxin-G1 and aflatoxin-G2), Alternaria toxins (alternariol, alternariol methyl ether and altenuene), fumonisins (fumonisin-B1, fumonisin-B2 and fumonisin-B3), ochratoxin A, zearalenone, beauvericin and sterigmatocystin in sweet pepper. Sweet pepper was extracted with ethyl acetate/formic acid (99:1, v/v). After splitting up the extract, two-thirds of the extract was cleaned up using an aminopropyl column followed by an octadecyl column. The remaining part was cleaned up using a strong anion-exchange column. After recombination of both cleaned parts of the sample extract, the combined solvents were evaporated and the residue was dissolved in mobile phase; 20,µL was injected into the chromatographic system, so only one run was used to separate and detect the mycotoxins in positive electrospray ionization using selected reaction monitoring. The samples were analyzed with a Micromass Quattro Micro triple quadrupole mass spectrometer (Waters, Milford, MA, USA). The mobile phase consisted of variable mixtures of water and methanol, 1% acetic acid and 5,mM ammonium acetate. The limits of detection of the multi-mycotoxin method varied from 0.32,µg.kg,1 to 42.48,µg.kg,1. The multi-mycotoxin liquid chromatography/tandem mass spectrometry (LC/MS/MS) method fulfilled the method performance criteria required by the Commission Regulation (EC) No 401/2006. Sweet peppers inoculated by Fusarium species were analyzed using the developed method. Beauvericin (9,484,µg.kg,1) and fumonisins (fumonisin-B1 up to 4330,µg.kg,1, fumonisin-B2 up to 4900,µg.kg,1, and fumonisin-B3 up to 299,µg.kg,1) were detected. Copyright © 2008 John Wiley & Sons, Ltd. [source] Rapid comprehensive amino acid analysis by liquid chromatography/tandem mass spectrometry: comparison to cation exchange with post-column ninhydrin detectionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2008Dennis J. Dietzen Ion-exchange chromatography with ninhydrin detection remains the gold standard for detecting inborn errors of amino acid catabolism and transport. Disadvantages of such analysis include long chromatography times and interference from other ninhydrin-positive compounds. The aim of this project was to develop a more rapid and specific technique using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Optimal fragmentation patterns for 32 amino acids were determined on a triple quadrupole mass spectrometer following butylation. Chromatographic characteristics of each of the amino acids were determined using C8 reversed-phase chromatography with 20% acetonitrile/0.1% formic acid as isocratic mobile phase. Quantitation using eleven deuterated internal standards was compared to cation exchange and ninhydrin detection on a Beckman 7300 system. Following methanol extraction and butylation, determination of 32 amino acids required 20,min. The dynamic range of each amino acid was generally 1,1000,µmol/L. Imprecision ranged from 7 to 23% (CV) over 6 months and recovery ranged from 88,125%. Deming regression with the Beckman 7300 yielded slopes from 0.4,1.2, intercepts from ,21 to 65,µmol/L, correlation coefficients from 0.84,0.99 and Syx from 2,125,µmol/L. Isobaric amino acids were separated by chromatography (e.g. leucine, isoleucine) or by unique fragmentation (e.g., alanine, , -alanine). LC/MS/MS is comparable to traditional LC-ninhydrin detection. Mass spectral detection shortens analysis times and reduces potential for interference in detecting inborn metabolic errors. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||