Showing papers on "Atmospheric-pressure chemical ionization published in 2002"
TL;DR: A liquid chromatography-mass spectrometry method to analyze total resveratrol in fruit products and wine found it to be stable for up to 5 days at 4 degrees C in the dark but was not stable at room temperature without protection from light.
Abstract: Resveratrol is an antioxidant found in grapes, grape products, and some other botanical sources with antiinflammatory and anticancer properties. In grapes and wine, it occurs both as free resveratrol and piceid, the 3β-glucoside of resveratrol. Here we report a liquid chromatography−mass spectrometry method to analyze total resveratrol (including free resveratrol and resveratrol from piceid) in fruit products and wine. Samples were extracted using methanol, enzymatically hydrolyzed, and analyzed using reversed phase HPLC with positive ion atmospheric pressure chemical ionization (APCI) mass spectrometric detection. Following APCI, the abundance of protonated molecules was recorded using selected ion monitoring (SIM) of m/z 229. An external standard curve was used for quantitation, which showed a linear range of 0.52−2260 pmol of trans-resveratrol injected on-column with a correlation coefficient 0.9999. The coefficient of variance of the response factor over the same concentration range was determined to ...
308 citations
TL;DR: ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols.
Abstract: Two mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed-phase high-performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed-phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI-MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI-MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI-MS. ESI-MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO](+) (acylium) ions, [RCOO+58](+) ions, and other related ions which allowed assignment of individual acyl chain identities. APCI-MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI-MS. APCI-MS/MS produced ions related to individual fatty acid chains. ESI-MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI-MS conditions. Fragmentation (MS/MS) of the [M+NH(4)](+) ions produced results similar to those obtained by APCI-MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols.
196 citations
TL;DR: LC/MS/MS exhibited high sensitivity and specificity for the detection of free steroids and may be a suitable technique for screening for the abuse of anabolic steroids in sports.
Abstract: The applicability of liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the detection of the free anabolic steroid fraction in human urine was examined. Electrospray ionization (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization methods were optimized regarding eluent composition, ion source parameters and fragmentation. The methods were compared with respect to specificity and detection limit. Although all methods proved suitable, LC/ESI-MS/MS with a methanol-water gradient including 5 mM ammonium acetate and 0.01% acetic acid was found best for the purpose. Multiple reaction monitoring allowed the determination of steroids in urine at low nanogram per milliliter levels. LC/MS/MS exhibited high sensitivity and specificity for the detection of free steroids and may be a suitable technique for screening for the abuse of anabolic steroids in sports.
191 citations
TL;DR: The applications of LC-MS to the studies of in vitro and in vivo drug metabolism, identification and characterization of impurities in pharmaceuticals, analysis of chiral impurity in drug substances and high-throughputLC-MS-MS systems for applications in the "accelerated drug discovery" process are described.
Abstract: The current developments in liquid chromatography-mass spectrometry (LC-MS) and its applications to the analysis of pharmaceuticals are reviewed. Various mass spectrometric techniques, including electrospray and nanospray ionization, atmospheric pressure chemical ionization and photoionization and their interface with liquid chromatographic techniques are described. These include high performance liquid chromatography, capillary electrophoresis and capillary electrochromatography and the advantages and disadvantages of each technique are discussed. The applications of LC-MS to the studies of in vitro and in vivo drug metabolism, identification and characterization of impurities in pharmaceuticals, analysis of chiral impurities in drug substances and high-throughput LC-MS-MS systems for applications in the “accelerated drug discovery” process are described.
171 citations
TL;DR: The integrated on-line SPE-HPLC-MS/MS system was successfully applied to the analysis of drinking and surface water samples taken from several sampling sites around the city of Leipzig, Germany, and Concentrations measured were far below the concentration limits scheduled by law.
142 citations
TL;DR: Despite 25 years of research in the identification of new DBPs, new ones are being discovered every year, even for chlorine which has been the most extensively studied.
Abstract: Gas chromatography-mass spectrometry (GC-MS) has played a pivotal role in the discovery of disinfection by-products (DBPs) in drinking water. DBPs are formed when disinfectants, such as chlorine, ozone, chlorine dioxide or chloramine, react with natural organic matter in the water. The first DBP known—chloroform—was identified by Rook in 1974 using GC-MS. Soon thereafter, chloroform and other trihalomethanes were found to be ubiquitous in chlorinated drinking water. In 1976, the National Cancer Institute published results linking chloroform to cancer in laboratory animals, and an important public health issue was born. Mass spectrometry and, specifically, GC-MS became the key tool used for measuring these DBPs in water and for discovering other DBPs that were formed. Over the last 25 years, hundreds of DBPs have been identified, mostly through the use of GC-MS, which has spawned additional health effects studies and regulations. Early on, GC with
low resolution electron ionization (EI)-MS was used, together with confirmation with chemical standards, for identification work. Later, researchers utilized chemical ionization (CI)-MS to provide molecular weight information and high resolution EI-MS to aid in the determination of empirical formulae for the molecular ions and fragments. More recently, liquid chromatography-mass spectrometry (LC-MS) with either electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) has been used to try to uncover highly polar DBPs that most experts believe have been missed by earlier GC-MS studies. Despite 25 years of research in the identification of new DBPs, new ones are being discovered every year, even for chlorine which has been the most extensively studied.
141 citations
TL;DR: Linear discriminant analysis (LDA) as a common multivariate mathematical-statistical calculation was successfully used to distinguish the oils based on their TAG composition and showed that 97.6% of the samples were classified correctly.
124 citations
TL;DR: Caffeine was detected in those areas previously identified for consistently exceeding the water quality criteria for fecal coliform bacteria contamination and there is a marked difference between samples collected in open bay areas and those collected from the Miami River.
109 citations
TL;DR: Identification and comparison of conjugates formed from the current model drugs were successfully analyzed in different biological specimens of common interest to biomedical research and a fairly good relation was obtained between the data from in vivo and in vitro models of drug metabolism.
Abstract: The applicability of different ionization techniques, electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and a novel atmospheric pressure photoionization (APPI), were tested for the identification of the phase II metabolites of apomorphine, dobutamine, and entacapone in rat urine and in vitro incubation mixtures (rat hepatocytes and human liver microsomes). ESI proved to be the most suitable ionization method; it enabled detection of 22 conjugates, whereas APCI and APPI showed only 12 and 14 conjugates, respectively. Methyl conjugates were detected with all ionization methods. Glucuronide conjugates were ionized most efficiently with ESI. Only some of the glucuronides detected with ESI were detected with APCI and APPI. Sulfate conjugates were detected only with ESI. MS/MS experiments showed that the site of glucuronidation or sulfation could not be determined, since the primary cleavage was a loss of the conjugate group (glucuronic acid or SO3), and no site-characteristic prod...
107 citations
TL;DR: A method for the determination of sulfonamides and trimethoprim in the complex matrix liquid manure has been developed using reversed-phase liquid chromatography and atmospheric pressure chemical ionization (APCI) tandem mass spectrometry and APCI proved to be more robust and less sensitive to matrix effects.
Abstract: A method for the determination of sulfonamides and trimethoprim in the complex matrix liquid manure has been developed using reversed-phase liquid chromatography and atmospheric pressure chemical ionization (APCI) tandem mass spectrometry. A comparison was made between electrospray and atmospheric pressure chemical ionization. APCI proved to be more robust and less sensitive to matrix effects. High-performance liquid chromatographic (HPLC) separation of the analytes was achieved in less than 7 min. The compounds were extracted with ethyl acetate and the extracts were cleaned up by solid-phase extraction on an aminopropyl column. Recoveries were not dependent on the concentration level. The mean recoveries were as follows: trimethoprim 79.0%, sulfadiazine 80.5%, N(4)-acetylsulfadiazine 91.0%, sulfamerazine 78.6%, sulfadimidine 77.2% and sulfamethoxazole 82.8%. Linearity was established over a concentration range of 5 to 5000 microg/kg with correlation coefficients greater than 0.99. The method had a limit of quantitation (LOQ) of 5 microg/kg manure.
103 citations
TL;DR: The position at which the fatty acids are esterified to the glycerol backbone can be elucidated by pSFC-APCI although it remains speculative whether this is valid for highly unsaturated triglycerides because reference compounds are not available to proof this.
TL;DR: An atmospheric pressure chemical ionization liquid chromatographic-mass spectrometric (APCI-LC-MS) LC-MS assay is presented for fast and reliable screening and identification as well as precise and sensitive quantification of oral antidiabetics of the sulfonylurea-type (OADs) in plasma as mentioned in this paper.
TL;DR: A liquid chromatography method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o-phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described.
TL;DR: In the absence of readily available reference compounds, approaches that can be taken to analyse anthocyanins by HPLC with absorbance and mass spectrometric detection are discussed.
TL;DR: In this article, an approach for simultaneous determination of the main type A-trichothecenes by liquid chromatography and atmospheric pressure chemical ionization mass spectrometry is described.
TL;DR: Three forensic samples, Booster DYNO, Semtex and Smokeless Powder, were analyzed to demonstrate the validity of the developed LC-MS methods.
TL;DR: The method was applied to the quantification of artemether and its metabolite in human plasma of healthy volunteers participating in pharmacokinetic drug-drug interaction studies and fully validated over a concentration range of 5-200 ng/ml.
TL;DR: The described LC-MSMS method allows the simultaneous determination of nicotine and eight of its major metabolites in urine of smokers with good precision and accuracy and is suitable for determining the nicotine dose in large-scale human biomonitoring studies.
Journal Article•
TL;DR: In this article, a method based on liquid chromatography tandem mass spectrometry (LC-MSMS) applying atmospheric pressure chemical ionisation (APCI) in the positive ion mode was developed for the direct determination of nicotine, cotinine, trans-3'-hydroxycotinine, their corresponding glucuronide conjugates as well as cotinines-N-oxide, norcotinines, and nicotine-N'-oxide in the urine of smokers.
TL;DR: APPI appears to be six to eight times more sensitive than APCI for idoxifene and its SB245419 metabolite; the response for theSB245420 metabolite is considerably better than for APCI conditions, but still not sufficient for trace level pharmacokinetic determinations in human plasma.
TL;DR: The results of these experiments clearly demonstrated the need for the careful evaluation of the isotopic integrity of the stable isotope labeled compound for the successful utilization of these compounds in BA studies and also as internal standards in the quantitative analysis of drugs in biological fluids.
TL;DR: A sensitive method for the separation and determination of amlodipine enantiomers in plasma has been developed based on solid-phase extraction (SPE) with disposable extraction cartridges (DECs) in combination with chiral liquid chromatography (LC).
TL;DR: The high explosives trinitrotoluene, nitroglycerine, pentaerythritol tetranitrate and hexahydro-1,3,5-trinitro- 1,3-5-triazine are efficiently ionised under negative ion atmospheric pressure chemical ionisation (APCI) conditions, demonstrating this to be a highly suitable method for enhancing the detection capabilities for explosives.
Abstract: The high explosives trinitrotoluene, nitroglycerine, pentaerythritol tetranitrate and hexahydro-1,3,5-trinitro-1,3,5-triazine are efficiently ionised under negative ion atmospheric pressure chemical ionisation (APCI) conditions. The limit of detection is improved, in some cases by several orders of magnitude, by complexation with chlorine demonstrating this to be a highly suitable method for enhancing the detection capabilities for explosives. The spectra produced from introduction of the analytes in a liquid matrix, with and without chlorine present, contain a number of ions that arise through secondary processes including breakdown and adduct formation. Sample introduction into an APCI source in air, via a heated-plate inlet with a supplementary feed of dichloromethane, produces improved response for the chloride adducts of the analytes and minimises their decomposition during analysis. The tandem mass spectra produced from the chloride adducts are simple. Optimisation of the trapping parameters of the ion trap detector enhances selected transitions, yields highly reproducible spectra and improves the limits of detection for MS/MS analysis.
TL;DR: The proposed method has been in routine use for more than 1 year and permits direct analysis of plasma samples without time-consuming sample preparation, which may be especially advantageous for clinical laboratories.
Abstract: A sensitive and specific direct-injection high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass-spectrometry (HPLC-APCI-MS-MS) method has been developed for the rapid identification and quantitation of seven tricyclic antidepressants-amitriptyline, nortriptyline, doxepin, dosulepin, dibenzepin, opipramol, and melitracen-in human plasma. After the addition of the internal standard lofepramine and dilution with 0.1% formic acid, plasma samples were injected into the LC-MS-MS system. Proteins and other large biomolecules were removed during an on-line sample cleanup using an Oasis extraction column (1 x 50 mm, ID, 30 microm) with a 100% aqueous mobile phase at a flow rate of 4 mL/min. The extraction column was subsequently brought in-line with the analytical column by automatic valve switching. Analytes were separated on a 5-microm Symmetry C18 (Waters) analytical column (3.0 x 150 mm, ID) using a step gradient of acetonitrile-0.1% formic acid at a flow rate of 0.6 mL/min. The total analysis time was only 12 minutes per sample. The interday and intraday coefficients of variation for all compounds were
Journal Article•
TL;DR: In this paper, a method for the simultaneous determination of a cyclooxygenase-2 inhibitor, 4-(4-methanesulfonylphenyl)-3-phenyl-5H-furan-2-one (rofecoxib, I) and [ 13 C 7 ] rofecoxideib, (II), in human plasma has been developed to support the clinical oral bioavailability (BA) study of I. The method is based on high-performance liquid chromatography (HPLC) with atmospheric pressure chemical ionization tandem mass spectrom
TL;DR: LC-MS with atmospheric pressure chemical ionization, in the negative-ion mode, was found to be the most suitable method for this study and the characterization of TNT by the by-product profile was demonstrated on a variety of TNT samples.
TL;DR: This work investigated the application of well-known and straightforward one-pot derivatization procedures to circumvent the limitations of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
Abstract: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is a powerful tool for the measurement of low molecular mass compounds of biological interest. The limitations for this method are the volatility of many analytes, possible interference with matrix signals or bad ionization or desorption behavior of the compounds. We investigated the application of well-known and straightforward one-pot derivatization procedures to circumvent these problems. The derivatizations tested allow the measurement and the labeling of alcohols, aldehydes and ketones, carboxylic acids, alpha-ketocarboxylic acids and amines.
TL;DR: Matrix-assisted laser desorption/ionization mass spectrometry has been demonstrated to be a powerful analytical technique for the analysis of polymeric materials as mentioned in this paper, which provides absolute, fast and accurate molecular masses for polymers with narrow polydispersity as opposed to relative masses provided by other techniques.
Abstract: Matrix-assisted laser desorption/ionization mass spectrometry has been demonstrated to be a powerful analytical technique for the analysis of polymeric materials. The advantages of this technique for such analyses include low sample consumption, ease of sample preparation, short analysis times, and soft ionization which leads to negligible or no fragmentation of analytes. It provides absolute, fast and accurate molecular masses for polymers with narrow polydispersity as opposed to relative masses provided by other techniques. It provides masses for the entire polymer distribution instead of the average value, hence providing molecular mass information which can be used to obtain the mass of the end-groups, mass of the repeat unit (monomer), and chemical modifications on the polymer if oligomer resolution is attained. This review concentrates on the developments in methodology that have allowed for the increased use of this technique for polymer analysis.
TL;DR: Preliminary results demonstrate that this technique provides approximately 150-fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI).
Abstract: We have designed and constructed an atmospheric pressure laser desorption/chemical ionization (AP-LD/CI) source that utilizes a laser pulse to desorb intact neutral molecules, followed by chemical ionization via reagent ions produced by a corona discharge. This source employs a heated capillary atmospheric pressure inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. Preliminary results demonstrate that this technique provides approximately 150-fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI).
TL;DR: A hitherto undetected type of C60O3 isomer was found in the reaction solution of C 60 with m-chloroperoxybenzoic acid by means of a chromatographic technique using two different columns as discussed by the authors.
Abstract: A hitherto undetected type of C60O3 isomer was found in the reaction solution of C60 with m-chloroperoxybenzoic acid by means of a chromatographic technique using two different columns. Both electronic spectroscopy and atmospheric pressure chemical ionization (APCI) mass-spectroscopy examinations show its C3ν symmetry, in which three oxygen atoms are added onto one benzenoid ring of C60.