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A simple and sensitive method was developed and validated here for the analysis of thirteen nonsteroidal anti-inflammatory drugs (NSAIDs) in human plasma samples by hydrophilic interaction liquid chromatography (HILIC)-tandem mass spectrometry (MS/MS). A small volume of plasma (20μL) spiked with compounds was diluted with 80μL of 10-mM ammonium acetate followed by a simple protein precipitation with 400μL of acetonitrile. After centrifugation, the clear supernatant extract was directly injected into the HILIC-MS/MS, without any solvent evaporation and reconstitution steps. The chromatographic separation of the NSAIDs was achieved on a Unison UK-Amino HILIC column (50mm×3mm i.d., particle size 3μm) with a linear gradient elution system composed of 10mM ammonium acetate (pH 6.8) and acetonitrile at a flow rate of 0.4mL/min. The mass spectra obtained by HILIC-MS showed base peak ions due to [M+H](+) for indomethacin, oxaprozin, ketoprofen, alminoprofen, zaltoprofen, tiaprofenic acid, pranoprofen, and ketoprofen-d3 and due to [M-H](-) for etodolac, ibuprofen, diclofenac, fenoprofen, loxoprofen, naproxen, and ibuprofen-d3. Recoveries of these thirteen NSAIDs in plasma were 34.8-113% and the lower limits of quantitation were 0.125-1.25μg/mL. The intra- and interday coefficient of variations for all drugs in plasma were less than 14.6%. The data obtained from actual plasma determinations of zaltoprofen, ibuprofen, and diclofenac are also presented.

Methamphetamine and amphetamine were extracted from human urine samples using pipette tip solid-phase extraction (SPE) with MonoTip C18 tips (pipette tip volume, 200 microl), in which C18-bonded monolithic silica gel was fixed. A sample of human urine (0.5 ml) containing methamphetamine, amphetamine, and N-methylbenzylamine as internal standard (IS), was mixed with 25 microl of 1M sodium hydroxide solution. The mixture was extracted into the C18 phase of the SPE tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. Analytes retained in the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. After derivatization with trifluoroacetic anhydride, analytes were measured by gas chromatography/mass spectrometry with selected ion monitoring in the positive-ion electron impact mode. Recoveries of methamphetamine, amphetamine, and IS spiked into urine were more than 82.9, 82.2, and 78.2%, respectively. Regression equations for methamphetamine and amphetamine showed excellent linearity in the range of 0.25-200 ng/0.5 ml. Limit of detection was 0.04 ng/0.5 ml for methamphetamine and 0.05 ng/0.5 ml for amphetamine. Intra- and inter-day coefficients of variations for both stimulants were not greater than 10.8%. The data obtained from actual determination of methamphetamine and amphetamine in autopsy urine samples are also presented for validation of the method.