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A sensitive method was developed for the simultaneous determination of midazolam and propofol in human plasma samples via modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction for their analysis by gas chromatography–tandem mass spectrometry (GC–MS/MS). Detailed optimization and validation experiments were conducted; plasma quality control samples spiked with two drugs and two internal standards (ISs) were extracted using the QuEChERS technique and determined by GC–MS/MS. The present method was applied to the measurements in an actual clinical case. The regression equations for midazolam and propofol in plasma displayed good linearity (r > 0.9978) from 10 to 1000 ng/mL with a limit of quantification of 10 ng/mL. The intra- and interday precisions for both drugs were not greater than 8.6%. The accuracies of quantitation ranged from 98 to 110%. The extraction efficiencies of midazolam and propofol for plasma were 93 to 117%. The method was successfully applied to the analyses of plasma midazolam and propofol concentrations in a brain-injured patient subjected to hypothermia, which validated the present methodology. In this study, the authors have successfully established the detailed procedure for GC–MS/MS analysis of midazolam and propofol in human plasma. The sensitivity and specificity of the present method for the drugs were almost comparable to those by the standard liquid chromatography–tandem mass spectrometry. To their knowledge, this is the first report for analysis of midazolam/propofol by GC–MS/MS.

Forensic toxicological analyses of drugs and their metabolites in human specimens usually require extractive pretreatment for successful analysis of substances from the matrix. In the present study, a high-throughput method was developed to analyze flunitrazepam, 7-aminoflunitrazepam, 7-acetamidoflunitrazepam, 7-acetamido-3-hydroxyflunitrazepam, and 3-hydroxyflunitrazepam in human plasma and urine samples using a new Monolithic C18 gel-packed SpinTip and ultra-performance liquid chromatography (UPLC)–quadrupole time-of-flight (Q-ToF) mass spectrometry (MS). Plasma (20 µL) or urine (100 µL) samples spiked with each component were extracted using a Monolithic C18 SPE SpinTip and quantified by UPLC–Q-Tof–MS with positive-ion electrospray ionization (ESI). Good separation, with clear peak shapes of flunitrazepam and its metabolites, was achieved within an analysis time of 6 min, including the extraction time. Recoveries of flunitrazepam and 7-aminoflunitrazepam for plasma and urine samples were 93.5–118% and 97.7–109%, respectively. The regression equations for flunitrazepam and 7-aminoflunitrazepam showed excellent linearity in the range of 0.5–250 ng/mL for plasma and 0.4–500 ng/mL for urine, with detection limits of 0.2–0.5 ng/mL. Intra- and inter-day coefficients of variations for two drugs are smaller than 13.5%. The accuracy of quantitation was 89–110%. The method was successfully applied to determine the level of flunitrazepam and its metabolites in human plasma and urine, respectively, after oral administration to a volunteer.

A high-throughput method was developed for determinations of eight barbiturates (barbital, allobarbital, phenobarbital, cyclobarbital, amobarbital, secobarbital, thiopental, and thiamylal) in human plasma by on-line column-switching ultra-fast liquid chromatography–tandem mass spectrometry (MS–MS). Plasma samples (100 μl) spiked with the eight barbiturates and 5-(4-methylphenyl)-5-phenylhydantoin (internal standard) were diluted with 300 μl of 13.3 mM ammonium acetate/acetonitrile (33:67, v/v). After centrifugation and filtration, the clear supernatant was injected directly onto the extraction column (Oasis HLB cartridge column). The following procedure was fully automated. The analytes retained on the extraction column were eluted by backflushing of the extraction column and introduced onto the analytical column (Phenomenex Onyx monolithic C18 column, 100 mm × 4.6 mm i.d.) by column switching. Quantification was performed by multiple reaction monitoring with negative-ion atmospheric pressure chemical ionization. Good peak separation and peak shapes of the eight drugs were achieved within an analysis time of 3 min, including the extraction time. All drugs spiked into plasma showed recoveries of 80–93 %. The regression equations for the eight drugs showed excellent linearities in the range of 10–5000 ng/ml of plasma, and the limits of detection ranged from 1.0 to 10 ng/ml. The lower and upper limits of quantitation were 10–50 ng/ml and 5000 ng/ml, respectively. Intraday and interday coefficients of variation for all the drugs were not >9.1 %. The accuracies of quantitation were 92.0–108 %. The method was successfully applied to determination of the level of amobarbital in human plasma after its oral administration to a volunteer.

Three tetracyclic antidepressants, mianserin, mirtazapine, and setiptiline, were extracted from human plasma samples using a new micropipette solid-phase extraction tip containing a monolithic silica gel packing material, the MonoTip C18. The plasma samples (0.1 ml), which contained mianserin, mirtazapine, and setiptiline, were mixed with 330 μl of distilled water and 50 μl of 0.5 M glycine–sodium hydroxide buffer solution (pH 8). After centrifugation, the supernatant was extracted onto the C18 phase of the tip (pipette tip volume, 200 μl) by 25 sequential aspirating/dispensing cycles. The three analytes retained in the C18 phase were eluted with methanol by 5 aspirating/dispensing cycles. The eluate was subjected to measurements by gas chromatography (GC) with nitrogen–phosphorus detection (NPD). The recoveries of the three antidepressants were 84.6–99.6% and the limits of detection for each drug were between 2.4 and 15 ng/ml of plasma. The maximum intraday and interday coefficients of variation for the drugs was below 10.6%. Regression equations for the three drugs showed excellent linearity in the range of 50–5000 ng/ml for mianserin and mirtazapine and 50–10 000 ng/ml for setiptiline. The antidepressants were stable for at least 12 h at 4°C, 4 weeks at −80°C, and through three freeze–thaw cycles in plasma. The validated method was successfully used to quantify the plasma concentrations of mirtazapine in a human subject after oral administration of the drug. Although we achieved analyte detection with GC-NPD, the present monolithic micropipette extraction method for tetracyclic antidepressants seems to be very useful for combining it with GC–mass spectrometry (MS) and/or liquid chromatography–tandem MS to secure high simplicity, purification, reproducibility, and sensitivity.

Six nonsteroidal anti-inflammatory drugs (NSAIDs) in human plasma samples were analyzed by liquid chromatography (LC)-electrospray ionizationtandem mass spectrometry (MS-MS) using a hydrophilic polymer column (MSpak GF-310 4B), which enabled direct injection of crude biological samples. Separation of the six NSAIDs, alminoprofen, flurbiprofen, ibuprofen, pranoprofen, tiaprofenic acid, and zaltoprofen, was carried out using gradient elution with 10 mM ammonium acetate/acetonitrile. The mass spectra obtained by LC-single stage MS showed base peak ions due to [M+H]+ for alminoprofen, zaltoprofen, tiaprofenic acid, and pranoprofen, and [M-H]- for ibuprofen and flurbiprofen. Product ions were produced from each [M+H]+ or [M-H]- ion in the tandem mode. Quantitation was performed by multiple reaction monitoring with switching from positive to negative ion mode and vice versa. All drugs spiked into plasma showed recoveries of 77.0%–88.2%. The regression equations for the six drugs showed excellent linearity in the range of 0.01–25 μg/ml of plasma, and limits of detection were in the range of 0.002–0.005 μg/ml. Limits of quantitation were 0.01–0.02 μg/ml. Intraday and interday coeffi cients of variation for all drugs in plasma were not greater than 8.1%. The accuracy of quantitating the six drugs was in the range of 94.5%–110%. Data obtained from actual determinations of the levels of alminoprofen, pranoprofen, and ibuprofen in human plasma after oral administration are also presented.

For forensic toxicological analysis of human specimens, extractive pretreatments are critical for successful analysis of target compounds. Nowadays, solidphase extraction (SPE) cartridges or columns packed with silica-type or polymer-type spherical particles are most widely used. In recent years, monolithic sorbent products, which have sponge-like structures, have been developed for SPE. The most significant advantage of the monolithic sorbent is that it allows very fast flow through the sorbent structure. Utilizing this property, pipette tips and spin columns packed with the monolithic sorbent have become commercially available. In this review, we present some details of SPE techniques using the monolithic pipette tips and spin columns, and discuss their advantages. The recent development of molecularly imprinted polymers (MIPs), which can selectively trap target compounds and act as an SPE sorbent, is also discussed with consideration of their advantages and disadvantages in SPE.

Methamphetamine and amphetamine were extracted from human whole blood samples using pipette tip solid-phase extraction (SPE) with MonoTip C(18) tips, on which C(18)-bonded monolithic silica gel was fixed. Human whole blood (0.1 mL) containing methamphetamine and amphetamine, with N-methylbenzylamine as an internal standard, was mixed with 0.4 mL of distilled water and 50 microL of 5 M sodium hydroxide solution. After centrifugation, the supernatant was extracted to the C(18) phase of the tip (pipette tip volume, 200 microL) by 25 repeated aspirating/dispensing cycles using a manual micropipettor. Analytes retained in the C(18) phase were 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 and amphetamine spiked into whole blood were more than 87.6 and 81.7%, respectively. Regression equations for methamphetamine and amphetamine showed excellent linearity in the range of 0.5-100 ng/0.1 mL. The limits of detection for methamphetamine and amphetamine were 0.15 and 0.11 ng/0.1 mL, respectively. Intra- and interday coefficients of variation for both stimulants were not greater than 9.6 and 13.8%, respectively. The determination of methamphetamine and amphetamine in autopsy whole blood samples is presented, and was shown to validate the present methodology.