Iván Álvarez

Determination of direct alcohol markers: a review

Alcohol is the most popular legal drug used in our society today, and its consumption by pregnant women remains an important public health problem. Gestational alcohol consumption can result in a continuum of adverse fetal outcomes known as fetal alcohol spectrum disorder (FASD). Effective strategies are needed to prevent the increasing adoption of risky drinking behaviors. Because ethanol itself is only measurable for a few hours after ethanol intake in conventional matrices including blood, urine, and sweat, these matrices are only useful to detect recent ethanol exposure. Since approximately early 2000, the non-oxidative ethanol metabolites have received increasing attention because of their specificity and, in some cases, wide time window of detection in non-conventional matrices including hair and meconium. In the attempt to update analytical methods for the determination of non-oxidative markers of alcohol, the objective of this study is to review published studies that measure fatty-acid ethyl esters (FAEE), ethyl glucuronide (EtG), and phosphatidylethanol (PEth) in alternative biological matrices, focusing on the extraction and detection methods and full analytical conditions used.

Optimization of ultrasound assisted dispersive liquid-liquid microextraction of six antidepressants in human plasma using experimental design

A simple Ultrasounds Assisted-Dispersive Liquid Liquid Microextraction (UA-DLLME) method is presented for the simultaneous determination of six second-generation antidepressants in plasma by Ultra Performance Liquid Chromatography with Photodiode Array Detector (UPLC-PDA). The main factors that potentially affect to DLLME were optimized by a screening design followed by a response surface design and desirability functions. The optimal conditions were 2.5 mL of acetonitrile as dispersant solvent, 0.2 mL of chloroform as extractant solvent, 3 min of ultrasounds stirring and extraction pH 9.8.Under optimized conditions, the UPLC-PDA method showed good separation of antidepressants in 2.5 min and good linearity in the range of 0.02-4 μg mL(-1), with determination coefficients higher than 0.998. The limits of detection were in the range 4-5 ng mL(-1). The method precision (n=5) was evaluated showing relative standard deviations (RSD) lower than 8.1% for all compounds. The average recoveries ranged from 92.5% for fluoxetine to 110% for mirtazapine. The applicability of DLLME/UPLC-PDA was successfully tested in twenty nine plasma samples from antidepressant consumers. Real samples were analyzed by the proposed method and the results were successfully submitted to comparison with those obtained by a Liquid Liquid Extraction-Gas Chromatography - Mass Spectrometry (LLE-GC-MS) method. The results confirmed the presence of venlafaxine in most cases (19 cases), followed by sertraline (3 cases) and fluoxetine (3 cases) at concentrations below toxic levels.

Determination of Cocaine and Heroin with Their Respective Metabolites in Human Hair using Gas Chromatography‐Mass Spectrometry

Abstract This paper describes a gas chromatography‐mass spectrometry method for the simultaneous detection of opiates, cocaine, and benzoylecgonine from human hair samples. Conditioning samples were extracted with Waters Oasis HLB (hydrophilic‐lipophilic balance) cartridges. The detector response was linear for the drugs studied over the range 0.5–20 ng/mg. The limits of quantitation and detection were found to be acceptable. Intra‐ and interbatch coefficients of variation oscillated between 0.2 and 17.9%, and mean relative errors were in the range of 0.04–18.2%. The recoveries were higher than 66.7% in all cases. Finally, the method was applied to 20 hair samples from drug users, obtaining positive results in all cases.

Analysis of Fatty Acid Ethyl Esters in Hair by Headspace Solid-Phase Microextraction (HS-SPME) and Gas Chromatography-Mass Spectrometry (GC-MS)

Abstract Fatty acid ethyl esters (FAEE) can be used as alcohol markers in hair. The purpose of this study was to validate a new method for the detection of FAEE in hair, reducing the extraction time. Hair samples were analyzed by gas chromatography-mass spectrometry after headspace solid-phase microextraction with deuterated internal standards. Linear curves for ethyl myristate, palmitate and stearate were obtained in the range considered. The limits of detection were 0.8, 0.005, and 0.01 and the lower limits of quantification were 1.8, 0.01, and 0.4 for ethyl myristate, palmitate and stearate, respectively. Intra- and inter-assay precision and accuracy were less than 12.5% and 16.1%, respectively. Recoveries were higher than 13.5% in all cases. Finally, the method was applied to analyze hair of alcoholics, social drinkers, and teetotallers.

Determination of fentanyl, metabolite and analogs in urine by GC/MS

A rapid and sensitive method for the simultaneous determination of alfentanyl, sufentanyl and fentanyl (and its major metabolite norfentanyl) in urine was developed and validated. The method involved a liquid–liquid extraction in alkaline conditions, derivatization with pentafluoropropionic anhydride to improve the sensitivity for norfentanyl and subsequent analysis in GC/MS. The LODs are 0.08 ng ml−1 for all substances (0.04 ng ml−1 for alfentanyl). Intra‐ and inter‐day precision coefficient of variation was always below 15%; mean relative error (accuracy) was always below 15%. The method was linear for all analytes, with quadratic regression of calibration curves always higher than 0.99. The method was applied to real samples of subjects who had received therapeutic doses of fentanyl, showing its suitability for the determination of low levels of these substances. The method was also applied to a subject whose death was attributed to fentanyl overdose. Copyright

Simultaneous Determination of Methadone, Heroin, Cocaine and their Metabolites in Urine by GC‐MS

Abstract A gas chromatographic‐mass spectrometric (GC‐MS) method for the determination of methadone, heroin, cocaine, and their metabolites in urine using Selected Ion Monitoring (SIM) was developed. Following a liquid‐liquid extraction with Toxitubes A® and using their deuterated analogs as internal standards, the analytes were derivatized with 99:1 (v/v) N,O‐bis‐trimethylsilyl‐trifluoroacetamide/trimethylchlorosilane and injected by hand, in the splitless mode, at 240°C and a purging time of 0.75 min. The mass selective detector was kept at 300°C and molecules were ionized in the electron impact mode, using an energy of 70 eV. The detector response was linear for all drugs studied over the range 50–1000 ng/mL.

Chromatographic determination of benzodiazepines in vitreous humor after microwave-assisted extraction

An analytical method was developed for the simultaneous determination of bromazepam, alprazolam, lorazepam, lormetazepam, diazepam and tetrazepam in vitreous humor, using microwave-assisted extraction (MAE) optimized by a central composite design followed by desirability functions, and high performance liquid chromatography coupled to a photodiode array detector (HPLC-PDA). The optimal conditions were 98 °C for the extraction temperature, 10 min for the extraction time, and ethyl acetate (10 mL) as the solvent. The extract was evaporated to dryness, redissolved in 100 μL of mobile phase, and injected (30 μL) into a XBridge™ Shield RP18 column (250 × 4.6 mm id, 5 μm particle size). The mobile phase, composed of acetonitrile and 0.02 M phosphate buffer pH 6, was eluted at a flow rate of 0.8 mL min−1 in gradient mode. The response of the detector was linear in the range of 0.05 to 5 μg mL−1 vitreous humor, the limits of detection ranged between 10 and 13 ng mL−1, and the coefficients of variation were always lower than 10%. The mean recoveries oscillated between 87.6% for diazepam and 101.2% for lormetazepam. Finally, the MAE/HPLC-PDA method was successfully applied to 16 vitreous humor samples from individuals intoxicated with benzodiazepines, with alprazolam, lormetazepam and diazepam being the most frequently found of these substances.