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At least 739 records · Page 41Linked to original sources
PubMed1995

Determination of the acylcoenzyme A cholesterol acyltransferase inhibitor 447C88 in plasma using gas chromatography-mass spectrometry and liquid chromatography atmospheric pressure chemical ionisation tandem mass spectrometry.

Two mass spectrometry-based methods are described for the determination of 447C88 (I), a novel inhibitor of acylcoenzyme A cholesterol acyltransferase (ACAT), in rat, dog and human plasma. The first method uses gas chromatography-mass spectrometry (GC-MS) with electron ionisation and selected-ion monitoring. The method employs solid-phase extraction of I from plasma and requires alkylation of I using iodoethane. The second method uses liquid chromatography-tandem mass spectrometry (LC-MS-MS) with atmospheric-pressure chemical-ionisation and selected-reaction monitoring. The LC-MS-MS method uses a simplified version of the extraction procedure used for GC-MS and does not require derivatisation of I. While both methods provide the necessary limit of quantitation of 0.5 ng/ml in human, dog and rat plasma with the required precision and accuracy, the LC-MS-MS assay offers increased sensitivity, selectivity and speed over the GC-MS assay. This allows a same day turn round of results for in excess of 100 samples, including sample preparation and data acquisition and processing.

Alkylation↗
PubMedDate not supplied

Determination of common drugs of abuse in body fluids using one isolation procedure and liquid chromatography--atmospheric-pressure chemical-ionization mass spectromery.

A method for determining opiate agonists (morphine, morphine-3-glucuronide, morphine-6-glucuronide, 6-monoacetylmorphine, codeine, codeine-6-glucuronide, dihydrocodeine, dihydromorphine, buprenorphine, methadone, tramadol, and ibogaine), cocaine and its metabolites (benzoylecgonine and ecgonine methyl ester) and lysergic acid diethylamide in serum, blood, urine and other biological matrices is presented. Aliquots (0.5-1.5 mL) of biological fluids were spiked with appropriate deuterated internal standards and extracted using a common solid-phase extraction method (C18 cartridges). The extracts were subjected to liquid chromatographic-atmospheric-pressure chemical-ionization mass spectrometric examination using selected ion monitoring procedures. These procedures were developed after analysis of full-scan mass spectra of examined compounds. The extraction method appeared very universal; the recoveries were high for almost all drugs and the extracts were very clean. The procedure was applied for routine forensic casework.

Body Fluids↗
PubMed1993

Determination of the beta-adrenergic blocker timolol in plasma by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A method based on LC-MS-MS has been developed for the determination of timolol in plasma using the (CD3)3-labelled species as the internal standard. Timolol is isolated from plasma by a simple solid-phase extraction and converted to its oxazolidin-2-one prior to analysis on a 50 x 4.6 mm reversed-phase high-performance liquid chromatography column packed with SynChropak, C18, 5 microns. The column eluate is passed by means of a heated nebulizer interface into a corona discharge atmospheric pressure chemical ionization source where the analyte and its internal standard are detected using multiple reaction monitoring (MRM). The very high specificity of this technique permits chromatographic run times of less than 2 min. The method has a lower quantifiable limit of 0.5 ng ml-1, with intra- and inter-day relative standard deviations less than 10%, and enables the determination of timolol in plasma after ocular administration to volunteers.

Calibration↗
PubMed2003

LC determination of impurities in methoxsalen drug substance: isolation and identification of isopimpinellin as a major impurity by atmospheric pressure chemical ionization LC/MS and NMR.

A gradient elution LC method was developed to separate methoxsalen from three of its known impurities: isopimpinellin, bergapten, and ammidin. The method employs a methanol-6%THF (aq) mobile phase, phenyl column, and detection at 254 nm. The gradient LC procedure was applied to seven lots of methoxsalen from five different manufacturers. Six of the seven lots tested contained isopimpinellin as the major impurity at a concentration range of 0.2-2.5%. Identification of the impurity as isopimpinellin was accomplished by a combination of analytical and preparative LC, atmospheric pressure chemical ionization liquid chromatography/mass spectrometry, and NMR.

Drug Contamination↗
PubMed2005

Determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in foods by high performance liquid chromatography-atmospheric pressure chemical ionisation-medium-resolution mass spectrometry.

A robust and sensitive method for the determination of ethylenethiourea (ETU) and iso-propylenethiourea (i-PTU) in foods is reported. ETU and i-PTU were extracted by blending with dichloromethane (DCM) in the presence of sodium sulphate, sodium carbonate, thiourea and ascorbic acid. 2H4-ETU and n-PTU were used as internal standards. After filtration the DCM was removed by rotary evaporation and the extract re-dissolved in water before analysis by reversed-phase liquid chromatography with detection by atmospheric pressure chemical ionization-mass spectrometry using a double focusing mass spectrometer at a resolution of 5000. Mean recoveries of ETU and i-PTU from fruit-based, cereal-based and meat-based infant foods, potato chips and tinned potatos at 0.01 mg kg(-1) and from pizza and yoghurt at 0.02-0.1 mg kg(-1) were 95% and 97% respectively. Precision, including both repeatability and internal reproducibility, was in the range of 3.1-13.1%.

Chromatography, High Pressure Liquid↗
PubMed1996

Extraction of maleic hydrazide residues from potato crisps and their determination using high-performance liquid chromatography with UV and atmospheric pressure chemical ionisation mass spectrometric detection.

A method was required for the determination of maleic hydrazide residues in potato crisps. A published method for the extraction of the analyte from onions and potatoes was evaluated and found to be inappropriate due to the inability of the extracting solvent to penetrate the oily matrix. A method was developed to overcome this problem; the resulting recovery data (mean = 92.9%, R.S.D. = 8.3%, n = 16) confirmed its efficiency, and was used to analyse 48 retail potato crisp samples. To confirm possible residues identified by screening with HPLC-UV, an HPLC-atmospheric pressure chemical ionization MS method was developed. There was good agreement between the data obtained from the two detection techniques (R2 = 0.978, slope = 1.11).

Chromatography, High Pressure Liquid↗