Paraquat (PQ) and diquat (DQ) in human whole blood and urine were analyzed by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) with positive ion electrospray ionization (ESI). The compounds were extracted with Sep-Pak C18 cartridges from whole blood and urine samples containing ethyl paraquat as an internal standard. The separation of PQ and DQ was carried out using ion-pair chromatography with heptafluorobutyric acid in 20 mM ammonium acetate and acetonitrile gradient elution for successful coupling with MS. Both compounds formed base peaks due to [M-H]+ ions by HPLC/ESI-MS and the product ions produced from each [M-H]+ ion by HPLC/MS/MS. Selective reaction monitoring (SRM) showed much higher sensitivity for both body fluids. Therefore, a detailed procedure for the detection of compounds by SRM with HPLC/MS/MS was established and carefully validated. The recoveries of PQ and DQ were 80.8-95.4% for whole blood and 84.2-96.7% for urine. The calibration curves for PQ and DQ showed excellent linearity in the range of 25-400 ng ml(-1) of whole blood and urine. The detection limits were 10 ng ml(-1) for PQ and 5 ng ml(-1) for DQ in both body fluids. The intra- and inter-day precision for both compounds in whole blood and urine samples were not greater than 13.0%. The data obtained from the determination of PQ and DQ in rat blood after oral administration of the compounds are also presented.

Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18- bonded monolithic silica gel was fixed. Human plasma (0.1 mL) containing the ten antihistamines was mixed with 0.4 mL of distilled water and 25 microL of a 1 M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30 m x 0.32 mm i.d., film thickness 0.25 microm). The recoveries of the ten antihistamines spiked into plasma were 73.8-105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02-5.0 ng/0.1 mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented.

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Diazepam and its major metabolites, nordazepam, temazepam and oxazepam, in human urine samples, were analyzed by liquid chromatography (LC)/tandem mass spectrometry (MS/MS) using a hydrophilic polymer column (MSpak GF-310 4B), which enables direct injection of crude biological samples. Matrix compounds in urine were eluted first from the column, while the target compounds were retained on the polymer stationary phase. The analytes retained on the column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. All compounds showed base-peak ions due to [M+H]+ ions on LC/MS with positive ion electrospray ionization, and product ions were produced from each [M+H]+ ion by LC/MS/MS. Quantification was performed by selected reaction monitoring. All compounds spiked into urine showed method recoveries of 50.1-82.0%. The regression equations for all compounds showed excellent linearity in the range of 0.5-500 ng/mL of urine. The limits of detection and quantification for each compound were 0.1 and 0.5 ng/mL of urine, respectively. The intra- and inter-day coefficients of variation for all compounds in urine were not greater than 9.6%. The data obtained from actual determination of diazepam and its three metabolites, oxazepam, nordazepam and temazepam, in human urine after oral administration of diazepam, are also presented.