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Chromatography/electrospray Ionization Tandem Mass Spectrometry (chromatography + ionization_tandem_mass_spectrometry)
Kinds of Chromatography/electrospray Ionization Tandem Mass Spectrometry Selected AbstractsRapid 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] Characterizing closely spaced, complex disulfide bond patterns in peptides and proteins by liquid chromatography/electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2002Ten-Yang Yen Abstract Identifying the Cys residues involved in disulfide linkages of peptides and proteins that contain complex disulfide bond patterns is a significant analytical challenge. This is especially true when the Cys residues involved in the disulfide bonds are closely spaced in the primary sequence. Peptides and proteins that contain free Cys residues located near disulfide bonds present the additional problem of disulfide shuffling via the thiol,disulfide exchange reaction. In this paper, we report a convenient method to identify complex disulfide patterns in peptides and proteins using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with partial reduction by tris(2-carboxyethyl)phosphine (TCEP). The method was validated using well-characterized peptides and proteins including endothelin, insulin, ,-conotoxin SI and immunoglobulin G (IgG2a, mouse). Peptide or protein digests were treated with TCEP in the presence of an alkylation reagent, maleimide-biotin (M-biotin) or N -ethylmaleimide (NEM), followed by complete reduction with dithiothreitol and alkylation by iodoacetamide (IAM). Subsequently, peptides that contained alkylated Cys were analyzed by capillary LC/ESI-MS/MS to determine which Cys residues were modified with M-biotin/NEM or IAM. The presence of the alkylating reagent (M-biotin or NEM) during TCEP reduction was found to minimize the occurrence of the thiol,disulfide exchange reaction. A critical feature of the method is the stepwise reduction of the disulfide bonds and the orderly, sequential use of specific alkylating reagents. Copyright © 2001 John Wiley & Sons, Ltd. [source] Determination of growth hormone secretagogue pralmorelin (GHRP-2) and its metabolite in human urine by liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010Masato Okano GHRP-2 (pralmorelin, D-Ala-D-(,-naphthyl)-Ala-Ala-Trp-D-Phe-Lys-NH2), which belongs to a class of growth hormone secretagogue (GHS), is intravenously used to diagnose growth hormone (GH) deficiency. Because it may be misused in expectation of a growth-promoting effect by athletes, the illicit use of GHS by athletes has been prohibited by the World Anti-Doping Agency (WADA). Therefore, the mass spectrometric identification of urinary GHRP-2 and its metabolite D-Ala-D-(,-naphthyl)-Ala-Ala-OH (AA-3) was studied using liquid chromatography/electrospray ionization tandem mass spectrometry for doping control purposes. The method consists of solid-phase extraction using stable-isotope-labeled GHRP-2 as an internal standard and subsequent ultra-performance liquid chromatography/tandem mass spectrometry, and the two target peptides were determined at urinary concentrations of 0.5,10,ng/mL. The recoveries ranged from 84 to 101%, and the assay precisions were calculated as 1.6,3.8% (intra-day) and 1.9,4.3% (inter-day). Intravenous administration of GHRP-2 in ten male volunteers was studied to demonstrate the applicability of the method. In all ten cases, unchanged GHRP-2 and its specific metabolite AA-3 were detected in urine. Copyright © 2010 John Wiley & Sons, Ltd. [source] Gas-phase formation of protonated benzene during collision-induced dissociation of certain protonated mono-substituted aromatic molecules produced in electrospray ionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Min Li Protonated benzene, C6H, has been studied extensively to understand the structure and energy of a protonated organic molecule in the gas phase. The formation of C6H is either through direct protonation of benzene, i.e., chemical ionization, or through fragmentation of certain radical cations produced from electron ionization or photon ionization. We report a novel observation of C6H as a product ion formed in the collision-induced dissociation (CID) of protonated benzamide and related molecules produced via electrospray ionization (ESI). The formation of C6H from these even-electron precursor ions during the CID process, which has not been previously reported, is proposed to occur from the protonated molecules via a proton migration in a five-membered ring intermediate followed by the cleavage of the mono-substituent CC bond and concurrent formation of an ion-molecule complex. This unique mechanism has been scrutinized by examining some deuterated molecules and a series of structurally related model compounds. This finding provides a convenient mean to generate C6H, a reactive intermediate of considerable interest, for further physical or chemical investigation. Further studies indicate that the occurrence of C6H in liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) appears to be a rather common phenomenon for many compounds that contain ,benzoyl-type' moieties. Hence, the observation of the C6H ion in LC/ESI-MS/MS can be used as an informative fragmentation pathway which should facilitate the identification of a great number of compounds containing the ,benzoyl-type' and similar structural features. These compounds are frequently present in food and pharmaceutical products as leachable impurities that require strict control and rapid elucidation of their identities. Copyright © 2010 John Wiley & Sons, Ltd. [source] Identification of metabolites of adonifoline, a hepatotoxic pyrrolizidine alkaloid, by liquid chromatography/tandem and high-resolution mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009Aizhen Xiong Hepatotoxic pyrrolizidine alkaloid (HPA)-containing plants have always been a threat to human and livestock health worldwide. Adonifoline, a main HPA in Senecio scandens Buch.-Ham. ex D. Don (Qianli guang), was used officially as an infusion in cases of oral and pharyngeal infections in China. In this study in vivo metabolism of adonifoline was studied for the first time by identifying the metabolites of adonifoline present in bile, urine and feces of rats using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MSn) (ion trap) as well as liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) (quadrupole-time of flight). In total 19 metabolites were identified and, among them, retronecine- N -oxides were confirmed by matching their fragmentation patterns with their fully characterized synthetic compounds. These metabolites are all involved in both phase I and phase II metabolic processes and the principal in vivo metabolism pathways of adonifoline were proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural elucidation of metabolites of ginkgolic acid in rat liver microsomes by ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry and hydrogen/deuterium exchangeRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009Z. H. Liu Ginkgolic acids have been shown to possess allergenic as well as genotoxic and cytotoxic properties. The question arises whether the metabolism of ginkgolic acids in the liver could decrease or increase their toxicity. In this study, the invitro metabolism of ginkgolic acid (15:1, GA), one component of ginkgo acids, was investigated as a model compound in Sprague-Dawley rat liver microsomes. The metabolites were analyzed by ultra-performance liquid chromatography coupled with photodiode array detector/negative-ion electrospray ionization tandem mass spectrometry (UPLC-PDA/ESI-MS/MS) and hydrogen/deuterium (H/D) exchange. The result showed that the benzene ring remained unchanged and the oxidations occurred at the side alkyl chain in rat liver microsomes. At least eight metabolites were found. Among them, six phase I metabolites were tentatively identified. This study might be useful for the investigation of toxicological mechanism of ginkgolic acids. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analysis of urinary nucleosides as helper tumor markers in hepatocellular carcinoma diagnosisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009Long-Bin Jeng Hepatocellular carcinoma (HCC) is a common neoplasm in Taiwan, for which early diagnosis is difficult and the prognosis is usually poor. HCC is usually diagnosed by abdominal sonography and serum alpha-fetoprotein (AFP) detection. Modified nucleosides, regarded as indicators for the whole-body turnover of RNAs, are excreted in abnormal amounts in the urine of patients with malignancies and can serve as tumor markers. We analyzed the excretion patterns of urinary nucleosides from 25 HCC patients and 20 healthy volunteers by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) under optimized conditions. The HPLC/ESI-MS/MS approach with selective reaction monitoring (SRM) allowed for the sensitive determination of nucleosides in human urine samples. The mean levels of the urinary nucleosides adenosine, cytidine, and inosine were significantly higher in HCC patients than healthy volunteers (average of 1.78-, 2.26-, and 1.47-fold, respectively). However, the mean levels of urinary 1-methyladenosine, 3-methylcytidine, uridine, and 2,-deoxyguanosine were not significantly different. Combined with the determination of serum AFP levels, the higher levels of urinary adenosine, cytidine, and inosine may be additional diagnosis markers for HCC in Taiwanese patients. 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] Plasma free fatty acid profiling in a fish oil human intervention study using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2008Nicole Zehethofer A rapid method was developed for the simultaneous profiling of 29 free fatty acids in plasma using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC/ESI-MS/MS). Barium acetate was used as the cationization agent in the positive ion mode for sensitive multiple reaction monitoring (MRM) experiments. The cis- and trans -C18:1 and -C18:2 isomers were baseline-separated using two tandem reversed-phase C18 UPLC columns, while identification of two pairs of positional isomers of C18:3 and C20:3 required isomer-specific product ions, as the analytes were not chromatographically resolved. The assay linearity was greater than three orders of magnitude and correlation coefficients were >0.99; the limits of detections were typically less than 0.2,µM. The method was successfully applied to plasma free fatty acid profiling of samples from volunteers who participated in a randomized crossover study involving the administration of either placebo or fish oil capsules. The results clearly indicate the ability to measure the time profiles of the n -3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in plasma for the volunteers given fish oil capsules while the concentrations of the other free fatty acids and the total free fatty acid concentration in plasma remained virtually constant. Copyright © 2008 John Wiley & Sons, Ltd. [source] Human urinary metabolite profile of tea polyphenols analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry with data-dependent acquisitionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2008Shengmin Sang Tea is rich in polyphenols and has a variety of biological activities. In order to better understand the biological effects of tea constituents on human health, markers for their exposure and their metabolic fates are needed. Previously, we have characterized several catechin metabolites in the blood and urine, but more information on the metabolite profile of tea polyphenols is needed. In the present study, the human urinary metabolite profile of tea polyphenols was investigated using liquid chromatography/electrospray ionization tandem mass spectrometry with data-dependent acquisition. With data-dependent MS/MS analysis by collecting the MS2 and MS3 spectra of the most intense ions in the sample, we identified more than twenty metabolites of tea polyphenols from human urine samples. (,)-Epigallocatechin (EGC) glucuronide, methylated EGC glucuronide, methylated EGC sulfate, (,)-epicatechin (EC) glucruronide, EC sulfate, methylated EC sulfate, as well as the glucuronide and sulfate metabolites of the ring-fission metabolites of tea catechins, 5-(3,,4,,5,-trihydroxyphenyl)- , -valerolactone (M4), 5-(3,,4,-dihydroxyphenyl)- , -valerolactone (M6) and 5-(3,,5,-dihydroxyphenyl)- , -valerolactone (M6,), were the major human urinary metabolites of tea polyphenols. To our knowledge, this is the first report of the direct simultaneous analysis of the human urinary metabolite profile of tea polyphenols using single sample analysis. This method can also be used for thorough investigations of the metabolite profiles of many other dietary constituents. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterization of covalent addition products of chlorogenic acid quinone with amino acid derivatives in model systems and apple juice by high-performance liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2008Susanne Schilling High-performance liquid chromatography (HPLC) coupled to electrospray ionization tandem mass spectrometry (ESI-MSn) was used to study the covalent interactions between chlorogenic acid (CQA) quinone and two amino acid derivatives, tert -butyloxycarbonyl-L-lysine and N -acetyl-L-cysteine. In a model system at pH 7.0, the formation of covalent addition products was demonstrated for both derivatives. The addition product of CQA dimer and tert -butyloxycarbonyl-L-lysine was characterized by LC/MSn as a benzacridine structure. For N -acetyl-L-cysteine, mono- and diaddition products at the thiol group with CQA quinone were found. In apple juice at pH 3.6, covalent interactions of CQA quinone were observed only with N -acetyl-L-cysteine. Taking together these results and those reported by other groups it can be concluded that covalent interactions of amino side chains with phenolic compounds could contribute to the reduction of the allergenic potential of certain food proteins. Copyright © 2008 John Wiley & Sons, Ltd. [source] Liquid chromatography/electrospray ionization tandem mass spectrometry validated method for the simultaneous quantification of sibutramine and its primary and secondary amine metabolites in human plasma and its application to a bioequivalence studyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2006Deepak S. Jain A high-throughput and sensitive bioanalytical method using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed for the estimation of sibutramine and its two metabolites (M1 and M2). The extraction of sibutramine, its metabolites and imipramine (internal standard (IS)) from the plasma involved treatment with phosphoric acid followed by solid-phase extraction (SPE) using a hydrophilic-lipophilic balanced HLB cartridge. The SPE eluate without drying and reconstitution was analyzed by LC/MS/MS, equipped with a with turbo ion spray (TIS) source, operating in the positive and multiple reaction monitoring (MRM) acquisition mode. Sample preparation by this method yielded extremely clean extracts with quantitative and consistent mean recoveries; 95.12% for sibutramine, 92.74% for M1, 95.97% for M2 and 96.60% for the IS. The total chromatographic run time was 3.0,min with retention times of 2.51, 2.13, 2.09,min for sibutramine, M1, M2 and imipramine, respectively. The developed method was validated in human plasma matrix, with a sensitivity of 0.1,ng/mL (coefficient of variance (CV), 2.07%) for sibutramine, 0.1,ng/mL (CV, 3.59%) for M1 and 0.2,ng/mL (CV, 4.93%) for M2. Validation of the method for its accuracy, precision, recovery, matrix effect and stability was carried out especially with regard to real subject sample analysis. The response was linear over the dynamic range 0.1 to 8.0,ng/mL for sibutramine and M1, and 0.2 to 16.0,ng/mL for M2 with correlation coefficients of r,,,0.9959 (sibutramine), 0.9935 (M1) and 0.9943 (M2). The method was successfully applied for bioequivalence studies in 40 human subjects with 15,mg capsule formulations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Potentials of ion trap collisional spectrometry for liquid chromatography/electrospray ionization tandem mass spectrometry determination of buprenorphine and nor -buprenorphine in urine, blood and hair samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2006Donata Favretto A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed for the analysis of buprenorphine (BUP) and nor -buprenorphine (NBUP) in biological fluids. Analytes are isolated from urine and blood, after addition of d4 -buprenorphine (d4 -BUP) as internal standard, by solid-phase extraction. Preparation of hair involves external decontamination, mechanical pulverization, overnight incubation in acidic medium, and neutralization prior to extraction. Enzymatic hydrolysis with , -glucuronidase may be performed to distinguish between free and total BUP. Chromatographic separation is accomplished by gradient elution on a cyanopropyl 2.1,×,150,mm column. Positive ion ESI and MS analyses are carried out in an ion trap mass spectrometer. The use of this mass analyzer allows effective collisional experiments to be performed on ESI-generated MH+ species. Abundant product ions are produced, which can be monitored together with precursor ions without losing sensitivity. Thus, assay selectivity is definitely increased with respect to LC/ESI-MS/MS methods in which only precursor ions are monitored. The method has good linearity (calibration curves were linear in the range 0.1,10,ng/mL in urine and blood, in the range 10,160,pg/mg in hair) and limits of detection of 0.05,ng/mL for both BUP and NBUP in blood and urine samples, of 4,pg/mg for both analytes in hair. Both intra- and inter-assay precision and accuracy were satisfactory at three concentrations studied: relative standard deviations were <13.7% in urine, <17.3% in blood, <17.8% in hair; percent deviation of the mean from the true value was always <10.5% in urine and blood, <16.1% in hair. The method can be used to determine both analytes in the urine and hair of drug addicts on replacement therapy, and in post-mortem blood specimens when there is suspicion of drug-related death. Copyright © 2006 John Wiley & Sons, Ltd. [source] Targeted comparative proteomics by liquid chromatography/matrix-assisted laser desorption/ionization triple-quadrupole mass spectrometry,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2006Jeremy E. Melanson Here we report the first application of a matrix-assisted laser desorption/ionization (MALDI) triple-quadrupole mass spectrometer for targeted proteomics. Employing an amine-specific isotopic labelling approach, the technique was validated using five randomly selected bovine serum albumin peptides differentially labelled at known ratios. An indirect benefit of the isotopic labelling technique is a significant enhancement of the a1 ion in tandem mass (MS/MS) spectra of all peptides studied. Therefore, the a1 ion was selected as the fragment ion for multiple reaction monitoring (MRM) in all cases, eliminating tedious method development and optimization. Accurate quantification was achieved with an average relative standard deviation (RSD) of 5% (n,=,5) and a detection limit of 14,amol. The technique was then applied to validate an important virulence biomarker of the fungal pathogen Candida albicans, which was not accurately quantified using global proteomics experiment employing two-dimensional liquid chromatography/electrospray ionization tandem mass spectrometry (2D-LC/ESI)-MS/MS. Using LC/MALDI-MRM analysis of five tryptic peptides, the protein PHR1 was found to be upregulated in the hyphal (pathogenic) form of C. albicans by a factor of 7.7,±,0.8. Copyright © 2006 John Wiley & Sons, Ltd. [source] High sensitivity determination of valproic acid in mouse plasma using semi-automated sample preparation and liquid chromatography with tandem mass spectrometric detectionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2005Vincenzo Pucci A high-throughput liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) assay using automated sample preparation has been developed for the determination of valproic acid (VPA) in mouse plasma. A liquid-handling system was programmed to prepare calibration standard solutions in plasma, as well as quality controls and clinical samples. Plasma protein precipitation was performed on a 96-well plate, and the collected supernatant was directly injected into a reversed-phase LC/ESI-MS/MS system in the negative ionization mode. The calibration curve for VPA was linear over a dynamic range of 0.15,100,µg/mL. The limit of detection was 75,ng/mL and the lower limit of quantitation was 150,ng/mL. Intra- and inter-day validation assays of the semi-automated plasma analysis showed satisfactory accuracy and precision. Copyright © 2005 John Wiley & Sons, Ltd. [source] Identification of heat-induced degradation products from purified betanin, phyllocactin and hylocerenin by high-performance liquid chromatography/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2005Kirsten M. Herbach Betanin, phyllocactin (malonylbetanin) and hylocerenin (3-hydroxy-3-methylglutarylbetanin) were isolated from purple pitaya (Hylocereus polyrhizus [Weber] Britton & Rose) juice, and their degradation products generated by heating at 85°C were subsequently monitored by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. Thermal degradation of phyllocactin and hylocerenin in purified solution excluding the alleged protective effects by the juice matrix is reported for the first time. Betanin was predominantly degraded by hydrolytic cleavage, while decarboxylation and dehydrogenation were of minor relevance. In contrast, hylocerenin showed a strong tendency to decarboxylation and dehydrogenation, hydrolytic cleavage of the aldimine bond occurring secondarily. Phyllocactin degradation was most complex because of additional decarboxylation of the malonic acid moiety as well as generation and subsequent degradation of betanin due to phyllocactin demalonylation. Upon prolonged heating, all betacyanins under observation formed degradation products characterized by an additional double bond at C2C3. Hydrolytic cleavage of the aldimine bond of phyllocactin and hylocerenin yielded previously unknown acylated cyclo -dopa derivatives traceable by positive ionization, while application of ESI(,) facilitated the detection of a glycosylated aminopropanal derivative and dopamine, which have never been described before as betanin degradation products. Copyright © 2005 John Wiley & Sons, Ltd. [source] Development of a multiresidue method for analysis of major Fusarium mycotoxins in corn meal using liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2005Chiara Cavaliere A sensitive and reliable liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed to determine, in a single run, eight trichothecenes, three fumonisins, zearalenone and , -zearalenol, in corn meal samples. LC and MS conditions were varied to find the best compromise in terms of sensitivity and separation. An acceptable compromise was obtained using a C18 column thermostatted at 45°C and a mobile phase gradient of methanol/water with 10,mmol/L formate buffer (pH 3.8). A multiple reaction monitoring program, in which fumonisins and trichothecenes (except nivalenol and deoxynivalenol) are acquired in positive ESI as [M+H]+ or [M+NH4]+, and all other compounds in negative ESI, was developed to match appropriate retention time windows. Sample preparation used a simple homogenization of the corn meal sample with acetonitrile/water (75:25, v/v) followed by extraction on a C18 cartridge and clean-up on a cartridge containing graphitized carbon black. Method detection limits were in the range 2,14,ng/g, with the exception of nivalenol (27,ng/g), deoxynivalenol (40,ng/g) and 15-acetyldeoxynivalenol (30,ng/g). Good accuracy (recoveries 81,104%) and precision (RSD 4,11%) were obtained by performing calibration using a spiked analyte-free extract. Copyright © 2005 John Wiley & Sons, Ltd. [source] Differential adduction of proteins vs. deoxynucleosides by methyl methanesulfonate and 1-methyl-1-nitrosourea in vitro,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2005Fagen Zhang The reactions of two model mutagenic and carcinogenic alkylating agents, N -methyl- N -nitrosourea (MNU) and methyl methanesulfonate (MMS), with proteins and deoxynucleosides in vitro, were investigated. The protein work used an approach involving trypsin digestion and high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS). This technique permitted identification of the specific location of protein adduction by both MNU and MMS with commercial apomyoglobin and human hemoglobin, under physiological conditions. MNU treatment resulted in predominantly carbamoylation adducts on the proteins, but in contrast only methylated protein adducts were found following treatment with MMS. Further analyses, using TurboSequest®, and the Scoring Algorithm for Spectral Analysis (SALSA), revealed that MNU carbamoylation was specific for modification of either the N-terminal valine or the free amino group in lysine residues of apomyglobin and human hemoglobin. However, MMS methylation modified the N-terminal valine and histidine residues of the proteins. Despite their clear differences in protein modifications, MNU and MMS formed qualitatively the same methylated deoxynucleoside adduct profiles with all four deoxynucleosides in vitro under physiological conditions. In light of their different biological potencies, where MMS is considered a ,super clastogen' while MNU is a ,super mutagen', these differences in reaction products with proteins vs. deoxynucleosides may indicate that these two model alkylating agents work via different mechanisms to produce their mutagenic and carcinogenic effects. Copyright © 2005 John Wiley & Sons, Ltd. [source] Analytical method for the quantitative determination of urinary ethylenethiourea by liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2003Cristina Sottani A direct, rapid and selective method for the quantitative determination of the ethylenethiourea (ETU) in human urine has been validated and is reported in the present study. It allows the accurate quantification of ETU in this complex matrix without the use of any internal standard as the sample cleanup is effective enough for the removal of interferences that could lead to ion suppression in the electrospray ionization (ESI) source. This simple and rapid purification system, based on the use of a Fluorosil phase of a BondElut® column followed by a liquid-liquid extraction procedure, achieves mean extracted recoveries, assessed at three different concentrations (2.5, 10.0, and 25.0,,g/L), always more than 85%. High-performance liquid chromatography (HPLC) with positive ion tandem mass spectrometry, operating in selected multiple reaction monitoring (MRM) mode, is used to quantify ETU in human urine. The assay is linear over the range 0,50,,g/L, with a lower limit of quantification (LOQ) of 1.5,,g/L and a coefficient of variation (CV) of 8.9%. The lower limit of detection (LOD) is assessed at 0.5,,g/L. The overall precision and accuracy were determined on three different days. The values for within- and between-day precision are ,,8.3 and 10.1%, respectively, and the accuracy is in the range 97,118%. The relative uncertainties for the LOQ and QC concentrations have been estimated to be 18 and 8%, respectively. The assay was applied to quantify ETU in human urine from growers that regularly handle ethylenebisdithiocarbamate pesticides in large crop plantations. The biological samples were collected at the start and end of the working day, and the ETU urine levels were found to vary between 1.9 and 8.2,,g/L. Copyright © 2003 John Wiley & Sons, Ltd. [source] Congener-specific analysis of hexabromocyclododecane by high-performance liquid chromatography/electrospray tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2003Wesley Budakowski A congener-specific method based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ES-MS/MS) in the negative ion mode was developed for the analysis of hexabromocyclododecane (HBCDD). On a C18 analytical column, with a methanol/water mobile phase, the , -isomer was completely resolved from the , - and , -isomers while the , - and , -isomers were sufficiently resolved at half their peak heights. The ES spray voltage strongly influenced the intensity of the ion signal. For MS, a source temperature of 500°C and a collision energy of 50,eV were found to be optimum for the [M,H], to Br, transition. Run-to-run and day-to-day (n,=,3) variability was minimal, with relative standard deviations of 2.6,4.1 and 2.4,4.4%, respectively. The limit of detection was 4,6,pg on-column. When applied to tissue samples from Lake Winnipeg fish both , - and , -isomers of HBCDD were found in low-ng/g (lipid corrected) concentrations. Copyright © 2003 John Wiley & Sons, Ltd. [source] A strategy for quantitative bioanalysis of non-polar neutral compounds by liquid chromatography/electrospray ionization tandem mass spectrometry: determination of TS-962, a novel acyl-CoA:cholesterol acyltransferase inhibitor, in rabbit aorta and liver tissuesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2001Jun-ichi Yamaguchi A strategy for the sensitive and reliable quantitative determination of non-polar neutral compounds in biological matrices by liquid chromatography/electrospray ionization tandem mass spectrometry is described in the context of assay development for TS-962, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, in rabbit aorta and liver tissues. The electrospray ionization (ESI) mass spectrum of this compound with a mobile phase of water/acetonitrile did not give abundant [M,+,H]+ ions, but did give alkali metal cation adducts such as [M,+,Na]+, [M,+,CH3CN,+,Na]+ and [M,+,K]+ ions. The cationized species are acknowledged as unsuitable precursor ions for selected reaction monitoring (SRM) for various reasons, such as difficulty in obtaining characteristic product ions in low-energy collision-induced dissociation, and irreproducibility of the adduct-ion intensities. To overcome this problem, a solution of 3.4,mM trifluoroacetic acid in 2-propanol was added to the mobile phase as a postcolumn additive, resulting in a decrease of the undesirable adduct formation and significant enhancement of [M,+,H]+ ion intensity. An attempt was then made to prevent the matrix effect by employing a column-switching system, which allowed direct injection of a large volume of 2-propanolic tissue homogenate (950,µL) followed by sufficient clean-up, separation, and ESI-SRM on-line. This enabled development of a sensitive and reliable assay method for TS-962 in rabbit aorta and liver tissues in the concentration range of 5,500,ng/g wet tissue using a 25-mg aliquot of tissue sample. Application of this method to the determination of aortic TS-962 levels at 24,h after repeated oral administration of this compound (3,mg/kg) once a day for 12 weeks to 1% cholesterol-fed rabbits is also presented. Results showed that TS-962 is well distributed to both the thoracic and abdominal aorta tissues, at levels higher than the 50% inhibitory concentration value of this compound for microsomal ACAT activity from rabbit aorta. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of benzofurazan derivatization reagents for short chain carboxylic acids in liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS)BIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Tomofumi Santa Abstract Benzofurazan derivatization reagents, 4-[2-(N,N -dimethylamino)ethylaminosulfonyl]-7-(2-aminopentylamino)-2,1,3-benzoxadiazole (DAABD-AP) and 4-[2-(N,N -dimethylamino) ethylaminosulfonyl]-7-(2-aminobutylamino)-2,1,3-benzoxadiazole (DAABD-AB), for short-chain carboxylic acids in liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) were synthesized. These reagents reacted with short chain carboxylic acids in the presence of the condensation reagents at 60°C for 60 min. The generated derivatives were separated on the reversed-phase column and detected by ESI-MS/MS with the detection limits of 0.1,0.12 pmol on column. Upon collision-induced dissociation, a single and intense product ion at m/z 151 was observed. These results indicated that DAABD-AP and DAABD-AB are suitable as the derivatization reagents in LC/ESI-MS/MS analysis. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis of benzofurazan derivatization reagents for carboxylic acids in liquid chromatography/electrospray ionization,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 11 2007Tomofumi Santa Abstract The applicability of benzofurazan derivatization regents to carboxylic acids analysis in LC/ESI-MS/MS (high-performance liquid chromatography/electrospray ionization tandem mass spectrometry) was examined. The product ion spectra of DAABD-AE {4-[2-(N,N -dimethylamino)ethylaminosulfonyl]-7-(2-aminoethylamino)-2,1,3-benzoxadiazole}, DAABD-PZ {4-[2-(N,N -dimethylamino)ethylaminosulfonyl]-7- N -piperazino-2,1,3-benzoxadiazole}, DAABD-PiCZ {4-[4-carbazoylpiperidin-1-yl]-7-[2-(N,N -dimethylamino)ethylaminosulfonyl]-2,1,3-benzoxadiazole}, DAABD-ProCZ {4-[2-carbazoylpyrrolidin-1-yl]-7-[2-(N,N -dimethylamino) ethylaminosulfonyl]-2,1,3-benzoxadiazole} and DAABD-Apy {4-[2-(N,N -dimethylamino)ethylaminosulfonyl]-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole}, and their acetylated compounds were obtained. An intense fragment ion at m/z 151 corresponding to (dimethylamino)ethylaminosulfonyl moiety was observed in each spectra, suggesting that these reagents were suitable for ESI-MS/MS analysis. DAABD-AE, DAABD-APy and DAABD-PZ were applied to the analysis of octanoic acid and it was found that DAABD-AE and DAABD-APy gave high signal intensity suitable for LC/ESI-MS/MS. Copyright © 2007 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography/electrospray ionization tandem mass spectrometry of hydroxylated uroporphyrin and urochlorin derivatives formed by photochemical oxidation of uroporphyrinogen IBIOMEDICAL CHROMATOGRAPHY, Issue 5 2007Malcolm Danton Abstract Hydroxylated uroporphyrin I and urochlorin I derivatives formed by photochemical oxidation of uroporphyrinogen I were separated by high-performance liquid chromatography and fully characterized by electrospray ionization tandem mass spectrometry. The porphyrins and chlorins were identified by analysis of their product ion spectra with each hydroxylated derivative giving a characteristic collision-induced dissociation fragmentation pattern. The porphyrins and chlorins characterized were meso -hydroxyuroporphyrin I, , -hydroxypropionic acid uroporphyrin I, , -hydroxypropionic acid uroporphyrin I, hydroxyacetic acid uroporphyrin I, trans- 7-hydroxy-8-spirolactoneurochlorin I, cis- 7-hydroxy-8-spirolactoneurochlorin I and trans- and cis- 7,8-dihydroxyurochlorins I. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||