Masaru Terada

Case report: Etizolam and its major metabolites in two unnatural death cases

A simultaneous analytical method for etizolam and its main metabolites (alpha-hydroxyetizolam and 8-hydroxyetizolam) in whole blood was developed using solid-phase extraction, TMS derivatization and ion trap gas chromatography tandem mass spectrometry (GC-MS/MS). Separation of etizolam, TMS derivatives of alpha-hydroxyetizolam and 8-hydroxyetizolam and fludiazepam as internal standard was performed within about 17 min. The inter-day precision evaluated at the concentration of 50 ng/mL etizolam, alpha-hydroxyetizolam and 8-hydroxyetizolam was evaluated 8.6, 6.4 and 8.0% respectively. Linearity occurred over the range in 5-50 ng/mL. This method is satisfactory for clinical and forensic purposes. This method was applied to two unnatural death cases suspected to involve etizolam. Etizolam and its two metabolites were detected in these cases.

Determination of dextromethorphan in human plasma using pipette tip solid-phase extraction and gas chromatography-mass spectrometry.

Dextromethorphan was extracted from human plasma samples (100xa0μL) using MonoTip C18 tips, which are packed with C18-bonded monolithic silica gel that is attached to the inside of the tip. The samples, which contained dextromethorphan and trimeprazine as an internal standard (IS), were mixed with 200xa0μL of distilled water and 50xa0μL of 1xa0mol/L glycine–sodium hydroxide buffer (pHxa010). The mixture was extracted to the C18 phase of the tip by 20 sequential aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five sequential aspirating/dispensing cycles. The eluate was injected directly into a gas chromatograph and detected by a mass spectrometer with selected ion monitoring in positive electron ionization mode. An Equity-5 fused silica capillary column (30xa0mu2009×u20090.32xa0mm i.d., film thickness 0.5xa0μm) gave adequate separation of the dextromethorphan, IS, and impurities. The recoveries of dextromethorphan and the IS spiked into plasma were >87.4%. The regression equation for dextromethorphan showed excellent linearity from 2.5 to 320xa0ng/mL of plasma, and the limit of detection was 1.25xa0ng/mL of plasma. The intraday and interday coefficients of variation were less than 10.5% and 14.7%, respectively. The accuracy ranged from 91.9% to 107%. The validated method was successfully used to quantify the plasma concentration of dextromethorphan in a human subject after oral administration of the drug.

Time-of-flight mass spectrometry (TOF-MS) exact mass database for benzodiazepine screening

Time-of-flight mass spectrometry coupled with liquid chromatography (TOF-MS) has been developed for screening and determination of benzodiazepines with an exact mass database. Benzodiazepines display similar chemical structures and molecular weights, and thus show similar mass spectra and protonated molecule ions. Discrimination of mass spectrometry at low resolving power using single liquid chromatography mass spectrometry (LC-MS) is commonly difficult. TOF-MS analysis was performed using a 1100 TOF (Agilent Technologies) equipped with a Zorbax C18 Extend column. Purine and fluorine compound solution was always introduced into the ion source, and real-time mass adjusting was performed. Specimens were prepared utilizing the liquid-liquid extraction procedure with 1-chlorobutane. Benzodiazepines are widely used in medical practice in Japan, and data acquired from TOF-MS measurements of 41 benzodiazepines, including active metabolites, were used to create an exact mass database. This database comprised molecular formulae, calculated exact masses and retention times. Calibrations were also included in a database. Precision for the 41 drugs was considered sufficient for quantitative analysis. In analysis of samples from patient who had taken > or =2 benzodiazepines, selectivity was improved using the TOF-MS exact mass database. TOF-MS is effective for forensic toxicology in discriminating between benzodiazepines with similar structure and metabolites.

A new method for quantitative determination of dimemorfan in human plasma using monolithic silica solid-phase extraction tips

Dimemorfan was extracted from human plasma samples (100 μL) using MonoTip C(18) tips, which were packed with a C(18)-bonded monolithic silica gel attached to the inside of the tip. The samples, which contained dimemorfan and trimeprazine as an internal standard (IS), were mixed with 300 μL of distilled water and 50 μL of 1M glycine-sodium hydroxide buffer (pH 10). The mixture was extracted onto the C(18) phase of the tip by 20 sequential aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C(18) phase were then eluted with methanol by five sequential aspirating/dispensing cycles. The eluate was injected directly into a gas chromatograph and detected by a mass spectrometer with selected ion monitoring in positive electron ionization mode. An Equity-5 fused silica capillary column (30 m × 0.32 mm i.d., film thickness 0.25 μm) gave adequate separation of the dimemorfan, IS, and impurities. The recoveries of dimemorfan and the IS spiked into plasma were ≥83%. The regression equation for dimemorfan showed excellent linearity from 0.25 to 32.0 ng/100 μL of plasma, and the limit of detection was 0.125 ng/100 μL of plasma. The maximum intra-day and inter-day relative standard deviations were 13%, while accuracy ranged from 88% to 105%. Dimemorfan was stable for at least 12 h at 4°C, 4 weeks at -80°C, and three freeze-thaw cycles in plasma. This new method is expected to have application as a pretreatment for the rapid, simple, and quantitative determination of dimemorfan in plasma samples.

Relationship between the matrix effect and the physicochemical properties of analytes in gas chromatography

The phenomenon “matrix-induced chromatographic response enhancement” (matrix effect) causes quantitative errors in gas chromatography (GC) analyses. This effect varies according to the analyte nature, matrix type and concentration, and GC-system parameters. By focusing on the physicochemical properties of analytes, a predictive model was developed for the matrix effect using quantitative structure–property relationships. Experimental values of the matrix effect were determined for 58 compounds in a serum extract obtained from solid-phase extraction as the matrix. Eight molecular descriptors were selected, and the matrix-effect model was developed by multiple linear regression. The developed model predicted values for the matrix effect without any further experimental measurements. It also indicated that the molecular polarity (particularly H-bond donors) and volume of the analyte increase the matrix effect, while hydrophobicity and increasing number of nonpolar carbon atoms in the analyte decrease the matrix effect. The model was applied to the analysis of barbiturates. The predicted values indicated that N-methylation decreases the matrix effect, and the relative predicted values were effective for the selection of an internal standard. The obtained insight into the matrix effect and the prediction data will be helpful for developing quantitative analysis strategies.

Simultaneous determination for oxicam non-steroidal anti-inflammatory drugs in human serum by liquid chromatography–tandem mass spectrometry

A high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) technique was developed for the simultaneous determination of five non-steroidal anti-inflammatory oxicam drugs (ampiroxicam, tenoxicam, piroxicam, meloxicam and lornoxicam) in human plasma. These five oxicam drugs and isoxicam (internal standard) were extracted from human plasma with an Oasis(®) MAX cartridge column and analysed on a Unison UK-C18 column (2.0 mm × 100 mm, 3 μm) with an acetonitrile:10mM formic ammonium buffer (pH 3.0) (50:50) mobile phase at 0.20 ml/min at 37°C. The analytes were detected using a tandem mass spectrometer, equipped with an electrospray ion source (ESI). The instrument was used in multiple-reaction-monitoring (MRM) mode. The extraction yields from a 200 μl human plasma sample (containing 10 ng of each drugs) with the Oasis(®) MAX cartridge column were 93.3-102.5%. The detection limits were 0.01-6.5 ng/ml (S/N=3). Our developed method is very useful for the simultaneous determination of five oxicam (non-steroidal anti-inflammatory) drugs in human plasma by LC/MS/MS.

An in vitro study on the interaction between ethanol and imipramine at

Imipramine is a tricyclic antidepressant that is widely used for the treatment of major depression. There is a possibility that toxic interactions occur following combined use of imipramine and intake of alcohol. In this study, we investigated the in vitro interaction between ethanol and imipramine at high concentrations by observing a mixed-function oxidation reaction using human liver microsomes. Imipramine and its three main metabolites (desipramine; 2-hydroxyimipramine, 2-OHI; 2-hydroxydesipramine, 2-OHD) were measured by high-performance liquid chromatography with ultraviolet detection. The production of 2-OHD, the main metabolite of imipramine, was significantly inhibited, by 15%–50% (P < 0.05), by ethanol, but that of desipramine or 2-OHI was not. These results suggest that enhanced toxicity is attained by simultaneous use of ethanol and high dose of imipramine in the human body.

Sensitive liquid chromatography/tandem mass spectrometry method for the simultaneous determination of nine local anesthetic drugs.

A high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) with electrospray ionization (ESI) procedure for the simultaneous determination of nine local anesthetic drugs (procaine, mepivacaine, lidocaine, ropivacaine, oxybuprocaine, tetracaine, bupivacaine, T-caine and dibucaine) in human serum is described. The chromatographic separation was performed on a Mightysil-RP-18 GP II column (2.0mm×150mm, particle size 5μm). The mobile phase consisted of 10mM acetic ammonium buffer (pH 5.4) and acetonitrile and was delivered at a flow rate of 0.20mL/min. The triple quadrupole mass spectrometer was operated in positive ion mode, and multiple reaction monitoring was used for drug quantification. Solid-phase extraction of the nine local anesthetic drugs added to the human serum was performed with an Oasis(®) HLB extraction cartridges column. The method was linear for the investigated drugs over the concentration range of 10-100ng/mL. The recoveries of these drugs were in the range of 81.4-144%. The standard deviation (SD) values for all analytes were <0.10 for both intraday and interday accuracy and precision. The selectivity, accuracy and precision of this method are satisfactory for clinical and forensic applications. The sensitive and selective method offers the opportunity for the simultaneous screening and quantification, for clinical and forensic purposes, of almost all local anesthetics available in Japan.

Analysis of quazepam and its metabolites in human urine by gas chromatography-mass spectrometry: application to a forensic case.

A sensitive method for the simultaneous determination of quazepam and two of its metabolites, 2-oxoquazepam and 3-hydroxy-2-oxoquazepam, in human urine was developed using gas chromatography-mass spectrometry (GC/MS) with an Rtx-5MS capillary column. The quazepam and its metabolites were extracted from human urine using a simple solid-phase extraction Oasis(®) HLB cartridge column, and the 3-hydroxy-2-oxoquazepam was derivatised using BSTFA/1%TMCS and pyridine at 60 °C for 30 min. The mass spectrometric detection of the analytes was performed in the full scan mode, m/z 60-480, and selected ion monitoring (SIM) mode, m/z 386, for quazepam; m/z 342, for 2-oxoquazepam; m/z 429, for 3-hydroxy-2-oxoquazepam-TMS; and m/z 284, for alprazolam-d5 (internal standard), by electron ionization. The calibration curves of quazepam and its metabolites in urine showed good linearity in the concentration range of 2.5-500 ng/0.2 ml of urine. The average recoveries of quazepam and its metabolites from 0.2 ml of urine containing 500 ng and 50 ng of each drug were 71-83% and 88-90%, respectively. The limits of detection of quazepam, 2-oxoquazepam and 3-hydroxy-2-quazepam in urine by the selected ion monitoring mode were 0.096-0.37 ng/ml. This method would be applicable to other forensic biological materials containing low concentrations of quazepam and its metabolites.

Rapid and simple analysis of oxazolobenzodiazepine drugs in sera by wide-bore capillary gas chromatography with nitrogen-phosphorus detection using on-column methylation

A rapid and simple method for determination of oxazolobenzodiazepines (oxazolam, haloxazolam, mexazolam, cloxazolam, and flutazolam) in sera was developed by gas chromatography (GC) using nitrogen-phosphorus detection (NPD) and a methyl silicone fused-silica wide-bore capillary (DB-1) column. Underivatized oxazolobenzodiazepine drugs gave relatively low sensitivity, because of decomposition during their passage through the column. On the other hand, on-column methylation of the oxazolobenzodiazepines with 0.4 mM trimethylanilium hydroxide in methanolic solution resulted in higher sensitivity; detection was possible at levels at least two to eight times lower than those without derivatization. The average recoveries of five oxazolobenzodiazepines from 0.5-ml volumes of sera containing 1.0 or 0.1 μg of each drug were 88–101% and 66–106%, respectively. The limits of detection of methylated oxazolobenzodiazepines by wide-bore capillary GC-NPD were 50–100pg on column. This method could be used for determination of the drugs in actual serum specimens with concentrations as low as 25–70ng/ml.