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At least 721 records · Page 40Linked to original sources
PubMed2004

Simultaneous determination of eight underivatized amphetamines in hair by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS).

The aim of this study was to develop, optimize, and validate an analytical procedure to determine a group of eight amphetamines, amphetamine (AMP), ephedrine (EP), methcathinone (MTC), paramethoxyamphetamine (PMA), methamphetamine (MA), methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), and methylenedioxyethylamphetamine (MDEA), in hair. The target substances were extracted with 1-chlorobutane after alkaline (1M NaOH) digestion and analyzed underivatized with high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). APCI-MS parameters such as fragmentor and capillary voltage, corona current, drying gas temperature and flow rate, vaporizer temperature, and nebulizer gas pressure were optimized with the application of flow injection analysis. Quantitation was performed using selected ion monitoring of protonated molecular ions of the studied drugs, and their deuterated analogues were used as internal standards. The limits of detection were 0.05 ng/mg for MA, MDA, MDMA, and MDEA; 0.10 ng/mg for EP and AMP; and 0.20 ng/mg for MTC and PMA. A linear response was observed for all drugs from 0 to 20 ng/mg. The method was applied to the determination of amphetamines in 93 authentic hair samples obtained from detoxification and methadone treatment patients, revealing the following concentrations: 0.17-17.28 ng/mg (EP), 0.52-2.08 ng/mg (MTC), 0.15-62.52 ng/mg (AMP), 0.10-16.52 ng/mg (MA), 0.10-0.88 ng/mg (MDMA), and 0.10-0.16 ng/mg (MDEA). MDA and PMA were never detected.

Amphetamines↗
PubMed2001

Structural elucidation of monoterpene oxidation products by ion trap fragmentation using on-line atmospheric pressure chemical ionisation mass spectrometry in the negative ion mode.

Based on ion trap mass spectrometry, an on-line method is described which provides valuable information on the molecular composition of structurally complex organic aerosols. The investigated aerosols were generated from the gas-phase ozonolysis of various C(10)H(16)-terpenes (alpha-pinene, beta-pinene, 3-carene, sabinene, limonene), and directly introduced into the ion source of the mass spectrometer. Negative ion chemical ionisation at atmospheric pressure (APCI(-)) enabled the detection of multifunctional carboxylic acid products by combining inherent sensitivity and molecular weight information. Sequential low-energy collision-induced product ion fragmentation experiments (MS(n)) were performed in order to elucidate characteristic decomposition pathways of the compounds. Dicarboxylic acids, oxocarboxylic acids and hydroxyketocarboxylic acid products could be clearly distinguished by multistage on-line MS. Furthermore, sabinonic acid and two C(9)-ether compounds were tentatively identified for the first time by applying on-line APCI(-)-MS(n).

Aerosols↗
PubMed1998

Simultaneous determination of six quinolones in pig muscle by liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry.

An LC-MS method is described for the confirmation of six quinolones (enrofloxacine, ciprofloxacine, marbofloxacine, danofloxacine, sarafloxacine and difloxacine) in pig muscle. The quinolones were extracted from muscle (2 g) with phosphate buffer (pH 7.4). After centrifugation, the extract was purified on a C18 solid-phase extraction cartridge. Samples were analysed by LC with gradient elution on a C18 column and detected by MS via an atmospheric pressure chemical ionisation interface. For each compound, an intense pseudo-molecular ion [M+H]+ is obtained. The assay is specific and reproducible and allows the confirmation of the six quinolones at the 7.5 micrograms kg-1 level in pig muscle.

Animals↗
PubMed2003

Pd-catalyzed carbonylative cross-coupling reactions by triorganoindiums: highly efficient transfer of organic groups attached to indium under atmospheric pressure.

[reaction: see text] A highly atom-efficient synthetic method of unsymmetrical ketones was developed by using trialkyl- and triarylindiums, which could be employed as effective cross-coupling partners in Pd-catalyzed carbonylative cross-coupling reactions with a variety of organic electrophiles. The present method produced unsymmetrical ketones and 1,4-diacylbenzenes in good yields with highly efficient transfer of almost all the organic groups attached to the indium under atmospheric pressure of CO gas in THF at 66 degrees C.

Journal Article↗
PubMed1998

Determination of dimetridazole, ronidazole and their common metabolite in poultry muscle and eggs by high performance liquid chromatography with UV detection and confirmatory analysis by atmospheric pressure chemical ionisation mass spectrometry.

A method was developed for the determination of the nitroimidazole compounds dimetridazole (DMZ) and ronidazole (RNZ) and their common metabolite, 2-hydroxymethyl-1-methyl-5-nitroimidazole (2-OH-M). Extracts obtained from a clean-up process using strong cation exchange (SCX) solid phase extraction (SPE) can be analysed either by high performance liquid chromatography with UV detection (HPLC-UV) or by high performance liquid chromatography with atmospheric pressure chemical ionisation mass spectrometry (HPLC-APCI-MS) as a confirmatory method. Up to 20 samples can be extracted in approximately 4 h. The HPLC-UV analysis had a limit of detection of 0.5 microgram kg-1. Validation in chicken muscle fortified at a concentration of 5 micrograms kg-1 gave recoveries of 75% DMZ, 77% RNZ and 81% 2-OH-M with RSDs of 16.4, 11.3 and 14.0%, respectively (n = 17). Validation in egg fortified at the same concentration gave recoveries of 77% DMZ, 80% RNZ and 80% 2-OH-M, with RSDs of 14.9, 22.0 and 18.2%, respectively (n = 18). The limit of detection of the HPLC-APCI-MS method was 0.1 microgram kg-1 for DMZ and RNZ and 0.5 microgram kg-1 for 2-OH-M. This method gave mean recoveries in fortified egg samples of 65% DMZ, 87% RNZ and 75% 2-OH-M with RSDs of 22, 11 and 14%, respectively (n = 10). The ratios of the peak areas of the molecular ion and a fragment ion were monitored as added confirmation of the presence of the analyte. Both the HPLC-UV screening procedure and the HPLC-APCI-MS confirmatory method have subsequently been used for the analysis of several hundred samples as part of UK surveillance programmes.

Animals↗
PubMed2005

Separation and detection of compounds in Honeysuckle by integration of ion-exchange chromatography fractionation with reversed-phase liquid chromatography-atmospheric pressure chemical ionization mass spectrometer and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis.

A hyphenated method for the isolation and identification of components in a traditional Chinese medicine of Honeysuckle was developed. Ion-exchange chromatography (IEC) was chosen for the fractionation of Honeysuckle extract, and then followed by concentration of all the fractions with rotary vacuum evaporator. Each of the enriched fractions was then further analyzed by reversed-phase liquid chromatography-atmospheric pressure chemical ionization mass spectrometer (RPLC-APCI/MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) with matrix of oxidized carbon nanotubes, respectively. It can be noted totally more than 117 components were detected by UV detector, APCI/MS and MALDI-TOF/MS in Honeysuckle extract except the 145 components identified by MALDI-TOF/MS alone with this integrated approach, and 7 of them were preliminary identified according to their UV spectra and mass spectra performed by APCI/MS and MALDI-TOF/MS, respectively. The obtained analytical results not only indicated the approach of integration IEC fractionation with RPLC-APCI/MS and MALDI-TOF/MS is capable of analyzing complex samples, but also exhibited the potential power of the mass spectrometer in detection of low-mass compounds, such as traditional Chinese medicines (TCMs) and complex biological samples.

Chromatography, Ion Exchange↗
PubMed2003

A high repetition rate (1 kHz) microcrystal laser for high throughput atmospheric pressure MALDI-quadrupole-time-of-flight mass spectrometry.

Sample throughput has been increased in many areas of proteomics, but the last significant advance in lasers used for matrix-assisted laser desorption/ionization (MALDI) was the introduction of cartridge-type N2 lasers (337 nm, 4-ns pulse widths, 1-30-Hz repetition rates) more than a decade ago. This report describes the application of a 1-kHz repetition rate Nd:YAG laser (355 nm, <500-ps pulse widths) for atmospheric pressure MALDI-QqTOFMS, and data obtained are compared to a conventional nitrogen laser. For example, the signal intensity for angiotensin II using the 1-kHz laser was in some cases enhanced by a factor of 80 and high-quality data could be obtained in as little as 1 s.

Journal Article↗
PubMed2003

Development of LC/MS/MS methods for cocktail dosed Caco-2 samples using atmospheric pressure photoionization and electrospray ionization.

Good reliability of Caco-2 permeability studies requires competent sampling and analytical methods to ensure the comparability of day-to-day experiments. In this work, two n-in-one LC/MS/MS methods based on two different ionization techniques were developed and validated for a group of reference compounds; eight of them are recommended by the Food and Drug Administration (FDA) for the evaluation of oral drug permeability. The performance of a new ionization technique, atmospheric pressure photoionization (APPI), as an interface for quantitative LC/MS analysis was evaluated in comparison to the electrospray ionization (ESI). Generally, the validation parameters, including sensitivity, accuracy, and repeatability, were comparable for the APPI and ESI methods. The main difference was that the linear quantitative range of APPI was 3-4 orders of magnitude (r(2) >/= 0.998) whereas in ESI it was typically 2-3 orders of magnitude (r(2) >/= 0.990). By the APPI and ESI methods, the simultaneous analysis of nine highly heterogeneous compounds was achieved within 5.5-7 min, which leads to significant savings in time and cost of the analyses. The successful validation data indicate the usefulness of both the methods for the rapid and sensitive (LOD values typically </=5 nM) testing of drug transport across the Caco-2 monolayers, and after case-specific modification, the methods enable the permeability screening of new drug candidates. The applicability and reliability of both methods was demonstrated with a real batch of Caco-2 samples, each providing similar values of apparent permeability (P(app)). In addition, the individual permeabilities of the compounds in the cocktail experiments correlated closely to the ones obtained from single-compound experiments.

Journal Article↗
PubMed2000

Atmospheric pressure chemical ionization multi-stage mass spectrometry in the characterization of stereoisomeric synthons of cyclopropane amino acids.

The mass spectrometric behaviour of (1S,2R)-, (1R,2R)-, (1R,2S)- and (1S,2S)-2-[(S)-2,2-dimethyl-1, 3-dioxolan-4-yl]-1-spiro-¿4'[2'-phenyl-5'(4'H)-oxazolone]¿ cyclopropane (2) and (1S,2R)-, (1R,2R)-, (1R,2S)- and (1S, 2S)-methyl-1-benzamido-2-[(S)-2,2-dimethyl-1, 3-dioxolan-4-yl]cyclopropanecarboxylate (3) was studied under atmospheric pressure ionization conditions and by multi-stage mass spectrometric (MS(n)) experiments performed with an ion trap. Interestingly, by using methanol as solvent, compounds 2 lead to [M + H + CH(3)OH](+) ions which, as proved by collisional experiments, exhibit the same structure of the corresponding compound 3. MS/MS of [MH](+) ions allows a clear characterization of the different stereoisomers, which give rise to specific fragmentation pathways, rationalized with respect to the structure of the neutral molecules.

Air Pressure↗
PubMed2006

Atmospheric pressure photoionization coupled to porous graphitic carbon liquid chromatography for the analysis of globotriaosylceramides. Application to Fabry disease.

Globotriaosylceramides (Gb(3)) are biological compounds implicated in Fabry disease, a lysosomal storage disease due to the deficient activity of alpha-D-galactosidase A, which results in an accumulation of Gb(3) in many organs. The naturally occurring samples are composed of mixtures of several molecular species differing by the structure of the alkyl chains and the nature of the sphingoid base. Atmospheric pressure photoionization mass spectrometry (APPI-MS) proved to be an efficient method for the analysis of globotriaosylceramide molecular species, both in direct injection and by coupling with liquid chromatography (LC). In the positive ion mode, in-source fragmentations yield very precious information that can be used to determine the structure of the alkyl chains. In the negative ion mode, the chloroform solvent participates to the analyte ionization by forming an adduct with chloride ions generated in situ. Combination of LC on a Porous Graphitic Carbon stationary phase and APPI-MS allowed the detection of a great number of species from biological samples isolated from Fabry patients. This method could be an interesting analytical tool for the biochemical investigation of (sphingo) lipid metabolism.

Biomarkers↗
PubMed2001

Atmospheric pressure chemical ionization mass spectrometric and visible spectrophotometric studies of copper(I) and copper(II) complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol.

Complexes of copper(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) formed in aqueous methanol in a wide range of pH (from acidic to alkaline) as well as copper(I)-5-Br-PADAP species formed in methanolic solutions were investigated by spectrophotometry and mass spectrometry. Pseudomolecular and fragment ions created in the atmospheric pressure chemical ionization (APCI) source confirmed the molecular masses of the complexes existing in the solvents and their structures. The structure of the Cu(II) complex with 5-Br-PADAP formed in acidic medium was proposed as CuR(R - H) (where R is the undissociated molecule of the reagent). The binding sites of the two bound reagent molecules were different: in one of them the oxygen atom of the dissociated phenolic group and the nitrogen atom from the azo (-N=N-) group took part in complex formation, whereas in the other only nitrogen atoms from the pyridyl ring and azo group were involved. The complex was stable and could not be reduced to Cu(I) species by use of standard reducing agents (ascorbic acid, hydroxylamine). In alkaline solutions the complex tended to polymerize and precipitated in media containing less than 80% of methanol. The copper(I)-5-Br-PADAP complex was extremely unstable and could be obtained (as a mixture with Cu(II) species) in media free of water or oxygen. For this complex, CuR(2) was proposed as the most probable structure. According to this proposal copper(I) reacted exclusively with nitrogen-containing binding sites and the undissociated phenolic group was not engaged in complex formation. In this system Cu(I)/Cu(II) electron transfer is very rapid, accelerated by a polar environment, e.g. in the presence of water molecules or dissolved oxygen.

Journal Article↗
PubMed1999

Sensitive determination of RDX, nitroso-RDX metabolites, and other munitions in ground water by solid-phase extraction and isotope dilution liquid chromatography-atmospheric pressure electro-spray [correction of chemical] ionization mass spectrometry.

Recent improvements in the LC-MS interface have increased the sensitivity and selectivity of this instrument in the analysis of polar and thermally-labile aqueous constituents. Determination of RDX, nitroso-RDX metabolites, and other munitions was enhanced using LC-MS with solid-phase extraction, 15N3-RDX internal standard, and electrospray ionization (ESI) in negative ion mode. ESI produced a five-fold increase in detector response over atmospheric pressure chemical ionization (APCI) for the nitramine compounds, while the more energetic APCI produced more than twenty times the ESI response for nitroaromatics. Method detection limits in ESI for nitramines varied from 0.03 microgram l-1 for MNX to 0.05 microgram l-1 for RDX.

Chromatography, Liquid↗
PubMed2006

Comparison of vacuum matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure MALDI (AP-MALDI) tandem mass spectrometry of 2-dimensional separated and trypsin-digested glomerular proteins for database search derived identification.

Mass spectrometric based sequencing of enzymatic generated peptides is widely used to obtain specific sequence tags allowing the unambiguous identification of proteins. In the present study, two types of desorption/ionization techniques combined with different modes of ion dissociation, namely vacuum matrix-assisted laser desorption/ionization (vMALDI) high energy collision induced dissociation (CID) and post-source decay (PSD) as well as atmospheric pressure (AP)-MALDI low energy CID, were applied for the fragmentation of singly protonated peptide ions, which were derived from two-dimensional separated, silver-stained and trypsin-digested hydrophilic as well as hydrophobic glomerular proteins. Thereby, defined properties of the individual fragmentation pattern generated by the specified modes could be observed. Furthermore, the compatibility of the varying PSD and CID (MS/MS) data with database search derived identification using two public accessible search algorithms has been evaluated. The peptide sequence tag information obtained by PSD and high energy CID enabled in the majority of cases an unambiguous identification. In contrast, part of the data obtained by low energy CID were not assignable using similar search parameters and therefore no clear results were obtainable. The knowledge of the properties of available MALDI-based fragmentation techniques presents an important factor for data interpretation using public accessible search algorithms and moreover for the identification of two-dimensional gel separated proteins.

Algorithms↗
PubMed2006

Separation and identification of compounds in Adinandra nitida by comprehensive two-dimensional liquid chromatography coupled to atmospheric pressure chemical ionization source ion trap tandem mass spectrometry.

A comprehensive two-dimensional liquid chromatographic (2D-LC) separation system based on the combination of a CN column and a Merck Chromolith Flash reversed-phase column was developed for the separation of components in Adinandra nitida, one type of traditional Chinese medicine (TCM). The two dimensions were connected by a ten-port, dual-position valve controlled automatically by software written in-house. The effluents were detected by both ultraviolet and atmospheric pressure chemical ionization source ion trap tandem mass spectrometry (MS). The calculated peak capacity of the 2D-LC-MS/MS system was above 1240. More than 57 components were resolved in the methanol extract from Adinandra nitida leaves, and five of these were identified based on their relative retention times, molecular weights and MS/MS spectra.

Chromatography, High Pressure Liquid↗
PubMed2002

Negative ion chemical ionization gas chromatography-mass spectrometry and atmospheric pressure chemical ionization liquid chromatography-mass spectrometry of low-dosed and/or polar drugs in plasma.

In clinical and forensic toxicology, doping control, and therapeutic drug monitoring, specific and sensitive detection and precise quantification of xenobiotics in biosamples are great challenges. Today, mass spectrometry techniques, coupled with gas chromatography or liquid chromatography, are the most powerful methods in analytic toxicology. The pros and cons of electron ionization (EI) and negative ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS) and of atmospheric pressure chemical ionization liquid chromatography-mass spectrometry (APCI-LC-MS) are described for determination of the low-dosed benzodiazepine flunitrazepam and its 7-amino and its nor-metabolite in plasma. In addition, application of NICI-GC-MS is described for sensitive chiral determination of amphetamine derivatives in plasma and application of APCI-LC-MS for screening, library-assisted identification, and validated quantification of oral antidiabetics and for validated quantification of the neuroleptic risperidone and its 9-hydroxy metabolite. These examples show that NICI-GC-MS and LC-MS are powerful tools for determination of low-dosed and/or rather polar drugs or poisons, thus becoming indispensable supplements to classic EI-GC-MS in clinical and forensic toxicology as well as in doping control.

Amphetamine↗
PubMedDate not supplied

Analysis of benzoylecgonine in dried blood spots by liquid chromatography--atmospheric pressure chemical ionization tandem mass spectrometry.

Residual samples from blood spots (i.e., whole blood spotted onto filter paper) are a useful source for epidemiological screening studies involving newborns. However, the small volume of blood available from residual blood spots complicates the assay. A method for analyzing benzoylecgonine (BZE; the primary metabolite of cocaine) in blood spots, in which the blood spot is eluted with aqueous ammonium acetate-methanol containing N-methyl trideuterated-BZE as an internal standard, followed by high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry using multiple reaction monitoring, has been developed. This approach provides a rapid, direct, sensitive (limit of detection, approximately 2 ng/mL, based on a 12-microL sample size), and highly specific means of determining BZE concentrations in blood spots. We have applied this method for confirmatory analyses in a large epidemiological study of the prevalence of cocaine use during late pregnancy.

Acetates↗
PubMed1983

Atmospheric pressure effects on tumor growth: hypobaric anoxia and growth of a murine transplantable tumor.

Inasmuch as solid tumor growth and some intervention methods for tumor control have often been related to the low oxygen levels in tumor tissue, and a special role for hypoxia, perhaps even in oncogenesis, has been suggested by observations of unexpectedly low tumor incidence in mice caged a lifetime in the environment of a simulated altitude, inbred C3H/HeN mammary tumor virus-positive mice bearing transplanted tumors (16/C murine mammary adenocarcinoma) were exposed to atmospheric pressure variants ranging from 0.33 to 2.0 in different sequences 24 hours/day. Breathing gases included air, 100% oxygen, and other nitrogen--oxygen combinations. Exposure to the pressure sequences was continuous, beginning on the third day after tumor inoculation and continuing until planned necropsy at 1, 2, or 3 weeks. Actual tumor weight was used as a measure of effect. Mice caged at simulated altitude had tumors that averaged 45% of the weight of control tumors. The maximum effect occurred with continuous 2-week exposure to 0.43 atm. beginning on day 3 of tumor growth. At necropsy, these experimental tumors weighed an average of 15% of the control tumor weight. Life-span studies showed a maximum of 36% increase in longevity in the hypobaric pressure-exposed mice when compared to that of unexposed controls.

Adenocarcinoma↗