Chika Hasegawa

Simple method for the determination of benzodiazepines in human body fluids by high-performance liquid chromatography–mass spectrometry

Abstract Three benzodiazepines, etizolam, brotizolam and lorazepam, have been analyzed from human plasma and urine samples by high-performance liquid chromatography–mass spectrometry (HPLC–MS) with a new polymer column (MSpak GF), which enabled direct injection of crude biological samples. The recoveries of the three benzodiazepines spiked into plasma and urine were 81.7–90.7 and 78.7–91.5%, respectively. The regression equations for the three benzodiazepines showed excellent linearity in the range 10–500xa0ngxa0ml−1 of plasma or urine. The detection limits were 2xa0ngxa0ml−1 for etizolam and brotizolam, 5xa0ngxa0ml−1 for lorazepam in both samples. The intra- and inter-day precisions for plasma and urine were not greater than 12.7%. The data obtained from determination of the benzodiazepines in rat plasma after oral administration of the drugs are also presented.

Simultaneous determination of β-blockers in human plasma using liquid chromatography–tandem mass spectrometry

A detailed procedure for the analysis of four beta-blockers, acebutolol, labetalol, metoprolol and propranolol, in human plasma by high-performance liquid chromatography (LC)-tandem mass spectrometry (MS-MS) using an MSpak GF column, which enables direct injection of crude plasma samples, is presented. Protein and/or macromolecule matrix compounds were eluted first from the column, while the drugs were retained on the polymer stationary phase of the MSpak GF column. The analytes retained on the column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. All drugs showed base peak ions due to [M + H]+ ions by LC-MS with positive ion electrospray ionization, and the product ions were produced from each [M + H]+ ion by LC-MS-MS. Quantification was performed by selected reaction monitoring. The recoveries of the four beta-blockers spiked into plasma were 73.5-89.9%. The regression equations for all compounds showed excellent linearity in the range 10-1000 ng/mL of plasma, with the exception of propranolol (10-800 ng/mL). The limits of detection and quantification for each drug were 1-3 and 10 ng/mL, respectively, of plasma. The intra- and inter-day coefficients of variation for all drugs in plasma were not greater than 10.9%.

Pipette tip solid-phase extraction and gas chromatography-mass spectrometry for the determination of mequitazine in human plasma.

Mequitazine has been found to be extractable from human plasma samples using MonoTip C(18) tips, inside which C(18)-bonded monolithic silica gel was fixed. Human plasma (0.1mL) containing mequitazine and cyproheptadine as an internal standard (IS) was mixed with 0.4mL of distilled water and 25muL of 1M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C(18) phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C(18) phase were then eluted with methanol by five repeated aspirating/dispensing cycles. Without evaporation and reconstitution, the eluate was injected into a gas chromatograph injector and detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of mequitazine and the IS from each other and from impurities was generally satisfactory using a DB-1MS capillary column (30mx0.32mm i.d., film thickness 0.25mum). The recoveries of mequitazine and the IS spiked into plasma were more than 90.0%. The regression equation for mequitazine showed excellent linearity in the range of 0.2-200ng0.1mL(-1), and the detection limit was 0.05ng0.1mL(-1)of plasma. The intra-day and inter-day coefficients of variation for mequitazine in human plasma were not greater than 8.16 and 9.24%, respectively. Accuracy for the drug was in the range of 90.0-97.4%. The data obtained from determination of mequitazine in human plasma after oral administration of the drug are also presented.

Utility of disk solid-phase extraction for whole blood samples: analysis of some tetracyclic antidepressants by gas chromatography with nitrogen-phosphorus detection

Four tetracyclic antidepressants, maprotiline, mianserin, mirtazapine, and setiptiline, were extracted from human whole blood and plasma samples by disk solid-phase extraction with Empore C18 cartridges. They were determined by gas chromatography (GC) with nitrogen-phosphorus detection. Recoveries of maprotiline, mianserin, mirtazapine, and setiptiline spiked into whole blood or plasma were more than 83%. Regression equations for the four drugs showed excellent linearity in the range of 25–1000 ng in 0.2 ml whole blood and in 0.5 ml plasma. The limits of detection for the drugs were 4.1–18.2 ng per 0.2 ml for whole blood and 3.4–13.5 ng per 0.5 ml for plasma. The limits of quantification for the four drugs were 25 ng in 0.2 ml whole blood and in 0.5 ml plasma. Intraday and interday coefficients of variation for the antidepressants in both human specimens were below 15%. The above data show that relatively hydrophobic and basic drugs in crude biological samples such as whole blood can be extracted by disk solid-phase extraction very efficiently and with good reproducibility, and suggest that the extraction method is also useful as pretreatments before more sophisticated detection methods such as GC-mass spectrometry (MS) and liquid chromatography-MS(-MS).

Extraction of Muscle Relaxants in Human Body Fluids by Solid‐Phase Extraction

Abstract Three muscle relaxants, tolperisone, eperisone, and tizanidine, were found to be extractable from human whole blood and urine samples by solid‐phase extraction (SPE) with a Sep‐Pak C18 cartridge. Their determination was made using capillary gas chromatography with nitrogen phosphorus detection. Recoveries of the three drugs were 80.0%–97.2% for whole blood and 82.0%–94.5% for urine. The coefficients of within‐day variation in terms of recovery for all compounds in whole blood and urine samples were 2.2%–9.1% and 6.9%–9.6%, respectively; those of day‐to‐day variation for the compounds in both samples were not greater than 18.1%. The regression equations for the compounds showed excellent linearity with detection limits of 1.6–7.7 ng mL−1 for whole blood and 6.0–8.0 ng mL−1 for urine. The data obtained for actual determination of tolperisone in a subject after ingestion of the drugs are also presented.