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At least 577 records · Page 32Linked to original sources
PubMed2004

High-throughput assay of rotenone in olive oil using atmospheric pressure chemical ionization tandem mass spectrometry.

A high-throughput method is presented for the determination of rotenone in contaminated matrices. The procedure involves atmospheric pressure chemical ionization tandem mass spectrometry with a triple-quadrupole instrument and the use as internal standard of a cycloadduct derivative of rotenone itself. The method was applied to the evaluation of the decay of rotenone in olives and olive oil at various times after exposure to the contaminant.

Indicators and Reagents↗
PubMed1998

Identification of main corticosteroids as illegal feed additives in milk replacers by liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry.

Corticosteroids were proposed as growth promoting agents to improve commercial quality of meat. We developed a liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry (LC-APCI-MS) method able to identify the presence in milk replacers, when given by mouth, of dexamethasone, betamethasone, flumethasone, triamcinolone, predinisotone, prednisolone, methylprednisolone, fludrocortisone and beclomethasone, at levels in the range of 20-100 ppb. C18 solid-phase extraction, LC-RP C8 column separation, data acquisition (positive ions) in the scan range m/z 200-550 allowed us to differentiate and identify compounds by protonated molecules, their methanolic adducts and fragmentation patterns.

Adrenal Cortex Hormones↗
PubMed1997

Development of a high-performance liquid chromatographic-atmospheric pressure chemical ionization-tandem mass spectrometric assay for beta-tigogenin cellobioside in human serum.

A specific high-performance liquid chromatographic-atmospheric pressure chemical ionization tandem mass spectrometric assay for the quantitative determination of beta-tigogenin cellobioside in human serum is described. Serum cleanup and acetylation of the analyte were required to achieve the desired lower limit of quantification, 10 ng/ml. The precision of the assay was better than 13% over a serum concentration range of 10-500 ng/ml.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

A preliminary study of the analysis of Cannabis by supercritical fluid chromatography with atmospheric pressure chemical ionisation mass spectroscopic detection.

A rapid method is described for the analysis of Cannabis products by supercritical fluid chromatography (SFC) coupled to atmospheric pressure chemical ionization-mass spectroscopic (APCI-MS) detection. The method had a shorter analysis time than GC-MS methods, without the need for derivatization prior to analysis. It was also faster than HPLC methods, with better resolution and definitive identification. Linearity of detector response to cannabidiol, delta 8-tetrahydrocannabinol, delta 9-tetrahydrocannabinol and cannabinol was established, the detection limits for mass on column being 0.55 ng, 1.20 ng, 0.69 ng and 2.10 ng respectively. The technique offers a means by which Cannabis products can be definitively identified in a single chromatographic run. Application to casework samples is described.

Cannabinoids↗
PubMed2004

Electron density and gas temperature from line broadening in an argon surface-wave-sustained discharge at atmospheric pressure.

We have used the collisional broadening of neutral argon lines to determine the electron density and gas temperature of a microwave discharge at atmospheric pressure. The gas temperature can be obtained from the Van der Waals broadening, provided that the Stark broadening is negligible. This can be achieved by using lines from low-lying levels (close to the ground state). On the other hand, lines corresponding to transitions from high-lying levels, which are more sensitive to Stark (quadratic) broadening, can be utilized to determine electron density. The electron density values obtained from the quadratic Stark broadening of argon atoms are in reasonable agreement with those derived from the linear Stark broadening of the H(beta) line. The proposed method ensures perturbation-free access to plasma parameters, which is not the case when adding hydrogen to the discharge, even in a small amount, to observe the Balmer series lines.

Journal Article↗
PubMed2003

Determination of carbon in aqueous solutions by atmospheric-pressure helium microwave induced plasma atomic emission spectrometry with gas-phase sample introduction technique.

A trace amount of carbon was determined by atmospheric-pressure helium microwave induced plasma atomic emission spectrometry (He-MIP-AES) with gas-phase sample introduction technique. This method was applied for the generation of a continuous flow of carbon dioxide by the acidification of carbonate ion and hydrogen carbonate ion for the determination of carbon. The generated carbon dioxide was separated from the solution by a simple gas-liquid separator, dried with a desiccant and swept into the MIP with helium carrier gas for analysis. Of the acids and drying agents investigated, hydrochloric acid for acidification and anhydrous calcium chloride as a desiccant were found to be the most appropriate for the generation of carbon dioxide. Under the optimized experimental conditions, the best attainable detection limits at C (I) 193.09 and C (I) 247.86 nm lines were 7.89 and 8.10 microg/l with linear dynamic ranges of 100 to 10,000 and 100 to 20,000 microg/l for carbon, respectively. The presence of many diverse elements and ions was found to cause a more or less depressing interference by the proposed technique. However, no interference was observed from the following elements and ions: Ca, K, Rb, Br-, Cl-, F- and I-. Finally, the present method has been applied to the determination of carbon in several water samples.

Journal Article↗
PubMed2005

Analysis of bufadienolides in the Chinese drug ChanSu by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry.

The qualitative analysis of bufadienolides in the Chinese drug ChanSu was performed using high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS/MS). Bufadienolides are the major bioactive constituents of ChanSu, which is used to treat heart failure and cancer in traditional Chinese medicine. The APCI-MS fragmentation behavior of bufadienolides was studied. For bufadienolides with only hydroxyl substituents, the fragmentation was characterized by successive eliminations of H(2)O and CO molecules, and the profile of MS/MS product ions was correlated with the number of hydroxyl groups. If a C-16 acetoxyl group was present, the fragmentation of [M+H](+) ions was triggered by initial loss of 60 Da (HOAc). The elimination of CO was significant for bufadienolides with a 19-formyl group, and the 19-hydroxyl group could be characterized by the loss of 30 Da (HCHO). These fragmentation rules were applied to the identification of bufadienolides in a methanolic extract of ChanSu, which was separated on a C(18) column with gradient elution. A total of 35 bufadienolides were identified, including four new constituents. The method established here facilitated the convenient and rapid quality control of ChanSu crude drug and its pharmaceutical preparations.

Bufanolides↗
PubMed1996

Determination of polar pesticides in ground water using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization.

A method is described for determination of pesticides in ground water by liquid chromatography combined with mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The study demonstrates the sensitivity of the technique, with detection limits for water samples of about 0.001-0.005 microgram/l, corresponding to 50-300 pg injected. Performance data for the method such as recovery, precision and linearity are also reported. It is illustrated that the technique is applicable for many different types of pesticide structures, such as triazines, phenylurea herbicides, acetanilides, organophosphorus insecticides, etc. Twelve different pesticides and pesticide degradation products are included in the study. The optimization of inlet conditions with respect to sheath gas pressure, vaporizer temperature, capillary temperature and corona current is reported. Applicability of the method for analysis of "real-world" ground water samples is demonstrated.

Chromatography, High Pressure Liquid↗
PubMed2003

Fragmentation of cationized phosphotyrosine containing peptides by atmospheric pressure MALDI/Ion trap mass spectrometry.

An investigation of phosphate loss from sodium-cationized phosphotyrosine containing peptide ions was conducted using liquid infrared (2.94 microm) atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) coupled to an ion trap mass spectrometer (ITMS). Previous experiments in our laboratory explored the fragmentation patterns of protonated phosphotyrosine containing peptides, which experience a loss of 98 Da under CID conditions in the ITMS. This loss of 98 Da is unexpected for phosphotyrosine, given the structure of its side chain. Phosphate loss from phosphotyrosine residues seems to be dependent on the presence of arginine or lysine residues in the peptide sequence. In the absence of a basic residue, the protonated phosphotyrosine peptides do not undergo losses of HPO(3) (Delta 80 Da) nor HPO(3) + H(2)O (Delta 98 Da) in their CID spectra. However, sodium cationized phosphotyrosine containing peptides that do not contain arginine or lysine residues within their sequences do undergo losses of HPO(3) (Delta 80 Da) and HPO(3) + H(2)O (Delta 98 Da) in their CID spectra.

Amides↗
PubMed1998

Application of liquid chromatography-atmospheric pressure chemical ionization mass spectrometry and tandem mass spectrometry to the determination of volatile nitrosamines in dry sausages.

A high-performance liquid chromatographic-atmospheric pressure chemical ionization mass spectrometric method was developed for the determination of volatile nitrosamines in dry sausages. Tandem mass spectrometry was applied for the detection of N-nitrosopyrrolidine, N-nitrosodiethylamine and N-nitrosopiperidine. N-nitrosomethylamine was detected by using the selected ion monitoring mode. The occurrence of the four different nitrosamines was monitored in 27 dry sausage samples and a correlation was observed between N-nitrosopyrrolidine and biogenic amines. Nitroso compounds are thus not only formed in heated conditions but formation can also occur during ripening of dry sausages by reaction between residual nitrite and amines formed during the fermentation process.

Animals↗
PubMed2005

Benzene-assisted atmospheric-pressure chemical ionization: a new liquid chromatography/mass spectrometry approach to the analysis of selected hydrophobic compounds.

Charge-exchange reactions involving benzene have been successfully exploited to increase the sensitivity of atmospheric-pressure chemical ionization mass spectrometry (APCI-MS) towards hydrophobic compounds of significant environmental relevance which are not detectable with the ordinary APCI techniques. Among them, good sensitivity have been found for (a) highly chlorinated biphenyl derivatives such as dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethene (DDE); (b) cyclopentadienes such as Aldrin and its epoxy derivatives Dieldrin and Endrin; and (c) dibenzofurans and dibenzo-para-dioxins such as 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) and 2,3,7,8-tetrachloro-dibenzo-para-dioxin (2,3,7,8-TCDD). The reactant benzene molecules were introduced into the source either through the nebulizer gas or by direct post-column addition of neat liquid, whereas the targeted compounds were analyzed using a high-performance liquid chromatography (HPLC) RP-18 column using methanol/water solutions as mobile phase. By using benzene as post-column reagent, positive ion mode detection was proven to be significantly enhanced as compared with APCI measurements carried out without benzene assistance.

Air Pollutants↗
PubMed2001

The use of particle beam mass spectrometry for the measurement of impurities in a nabumetone drug substance, not easily amenable to atmospheric pressure ionisation techniques.

Liquid chromatography/particle beam mass spectrometry (LC/PB-MS) was used for the structural elucidation of some impurities in nabumetone as this compound poorly ionises by atmospheric pressure ionisation (API) techniques. PB-MS was optimised for nabumetone and a sensitivity study was carried out. To obtain full scan electron ionisation spectra a minimum of 100 ng of compound on column was needed. By using 20 mg/mL solutions of nabumetone, impurities at levels of about 250 ppm mass fraction relative to nabumetone could be detected. Results were compared with LC/API-MS and previous GC/MS.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Optimization of quartz tube pyrolysis atmospheric pressure ionization mass spectrometry for the generation of bacterial biomarkers.

Experimental procedures were investigated to improve the efflux of biomolecule pyrolyzates from quartz tube pyrolysis under atmospheric pressure ionization mass spectrometry conditions. Heating regimes, airflows, and ion focusing parameters were optimized to increase the informative mass spectral signals generated from the pyrolysis of Gram-positive bacterial spores and vegetative cells. Dipicolinic acid (DPA) is found in 5-15% by weight in Gram-positive Bacillus spores, and the parameter optimization procedures provided an intense mass spectral signature of the m/z 168 protonated DPA molecule with a minimization of pyrolytic and ionization fragments. Moreover, mass spectral information from the optimization protocols yielded peaks and mass patterns characteristic of DNA and RNA nitrogen bases, protein diketopiperazines, and amino sugars.

Bacillus↗
PubMed2001

An atmospheric pressure glow discharge optical emission source for the direct sampling of liquid media.

A glow discharge optical emission spectroscopy (GD-OES) source that operates at atmospheric pressure is described. This device utilizes an electrolytic solution containing the analyte specimen as one of the discharge electrodes. The passage of electrical current (either electrons or positive ions) across the solution/gas phase interface causes local heating and the volatilization of the analyte species. Collisions in the discharge region immediately above the solution surface result in optical emission that is characteristic of the analyte elements. Operation of this device with the analyte solution acting as either the cathode or anode is demonstrated. Current-voltage (i-V) plots reveal abnormal glow discharge characteristics, with operating parameters being dependent on the electrolyte concentration (i.e., solution conductivity) and the gap between the solution surface and the counterelectrode. Typical conditions include discharge currents of 30-60 mA, and potentials of 500-900 V. Electrolyte solutions having pH, pNa, or pLi values of 0.5-2 and interelectrode gaps of 0.5-3 mm produce stable plasmas in which the analyte solutions flow at rates of up to 3.0 mL/min. Preliminary limits of detection are determined for the elements Na, Fe, and Pb to be in the range of 11-14 ppm (approximately 60 ng) for 5-microL sample volumes.

Journal Article↗
PubMed1998

Quantification of 17 beta-estradiol residues in bovine serum by liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization.

A method for the quantification of the natural hormone 17 beta-estradiol (17 beta-E2) in bovine serum by liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS-MS) was developed. Ethinylestradiol (EE2) was used as internal standard. Analytes were extracted from serum using acetate buffer, purified by C18 solid-phase extraction (SPE) and chromatographed on a polymeric reversed-phase (PLRP-S) LC column. They were ionized in a heated nebulizer (HN) interface operating in the negative ion mode, where only the intact deprotonated molecules, [M - H]-, were generated at m/z 271 and 295 for 17 beta-E2 and EE2, respectively. These served as precursor ions for collision-induced dissociation (CID) and diagnostic product ions were identified for the unambiguous hormone confirmation by selected reaction monitoring (SRM) LC-APCI-MS-MS. The method was validated on bovine serum and the limit of quantification (LOQ) was 30 pg ml-1 for 17 beta-E2. The inter-day precision (relative standard deviation, RSD) and accuracy (relative error, RE) derived from the analyses of validation samples at three concentrations ranged from 1.76 to 3.76 and from -4.18 to -2.01%, respectively. This method is currently being successfully applied to measure the bovine serum concentration of 17 beta-E2 in order to discriminate between the physiological concentrations of 17 beta/E2 and the hormone levels resulting from illegal administration.

Anabolic Agents↗
PubMed1996

Analytical methods for the determination of sterigmatocystin in cheese, bread and corn products using HPLC with atmospheric pressure ionization mass spectrometric detection.

Methods have been developed for the determination of sterigmatocystin in bread, maize and cheese using HPLC linked to mass spectrometry (MS) atmospheric pressure chemical ionization for detection and concurrent confirmation of sterigmatocystin at levels down to less than 5 micrograms/kg. Candidate extraction methods were initially checked for recovery and reproducibility by spiking commodities at a level of 200 micrograms/kg of sterigmatocystin and using HPLC with post-column derivatization. Recovery was found to be greater than 90% for bread and maize, and 75% for cheese. Mass spectrometer conditions for detecting sterigmatocystin were established by injecting solutions directly into the mass spectrometer. Extracts of bread, maize grits and cheese prepared by the candidate extraction methods were examined using HPLC/MS using samples spiked at a level of 20 micrograms/kg of sterigmatocystin. Results for bread and maize samples showed that the extraction procedure recovered more than 90% of added sterigmatocystin and produced extracts free of interference from co-extractives, with limits of detection of less than 2 micrograms/kg for both commodities. The HPLC/MS results for cheese extracts gave lower average recoveries of 55%. These results were also more variable. However, the apparent limit of detection for sterigmatocystin in cheese was still about 4 micrograms/kg.

Bread↗