Long-term stability of synthetic cathinones in dried blood spots and whole blood samples: a comparative study

Dried matrix spots in forensic toxicology

Dried matrix spots (DMS) has gained the attention of different professionals in different fields, including toxicology. Investigations have been carried out in order to assess the potential of using DMS for the analysis of illicit substances, the main interest of forensic toxicologists. This technique uses minimal volumes of samples and solvents, resulting in simple and rapid extraction procedures. Furthermore, it has proved to increase analyte stability, improving storage and transportation. However, DMS presents some limitations: the hematocrit influencing accuracy and inconsistencies regarding the means of spotting samples and adding internal standard on paper. Thus, we provide an overview of analytical methodologies with forensic applications focusing on drugs of abuse and discussing the main particularities, limitations and achievements.

Stability of synthetic cathinones in clinical and forensic toxicological analysis-Where are we now?

Understanding the stability of analyzed drugs in biological samples is a crucial part for an appropriate interpretation of the analytical findings. Synthetic cathinones, as psychoactive stimulants, belong to a major class of new psychoactive substances. As they are subject to several degradation pathways, they are known to clinical and forensic toxicologists as unstable analytes in biological samples. When interpreting analytical data of synthetic cathinones in biological samples, analysts must be aware that the concentration of analytes may not accurately reflect the levels at the time they were acquired owing to many factors. This review provides (i) an overview of the current scientific knowledge on the stability of synthetic cathinones and/or metabolites in various human biological samples with a focus on factors that may deteriorate their stability-such as storage temperature, length of storage, matrix, pH, type of preservatives, concentration of analytes, and the chemistry of the analytes-and (ii) possible solutions on how to avoid such degradation. The PubMed database as well as Google Scholar was thoroughly searched to find published studies on the stability of synthetic cathinones since 2007 by searching specific keywords. A total of 23 articles met the inclusion criteria and were included in this review. Synthetic cathinones that carry methylenedioxy or N-pyrrolidine ring showed higher degradation resistance over other substituted groups. Acidification of samples pH plays a crucial role at increasing the stability of cathinones even with analytes that were frequently considered as poorly stable. This review also provides several recommendations for best practice in planning the experimental design, preservation, and storage conditions in order to minimize synthetic cathinones' degradation in human biological samples.

Extended Stability Evaluation of Selected Cathinones

Understanding the stability of drugs in a forensic toxicology setting is critical for the evaluation of drug concentrations. Synthetic cathinones are new psychoactive substances structurally derived from cathinone, the psychoactive component of Catha edulis ("khat"), a shrub that is indigenous to the Middle East and East Africa. Previous research has evaluated the stability of synthetic cathinones in biological matrices, including blood preserved with the combination of NaF and K2C2O4 used in gray-top tubes. However, it does not assess their stability in blood preserved with Na2EDTA, used for some clinical samples. Further, stability in unpreserved urine samples was only studied for two weeks. This research evaluates the stabilities of four Schedule I synthetic cathinones: mephedrone, MDPV (3,4-methylenedioxypyrovalerone), naphyrone, and α-PVP (alpha-pyrrolidinopentiophenone) at 20°C (room temperature), 4°C (refrigerator), and -20°C (freezer). Stability was assessed in methanolic and acetonitrile solutions, as well as in Na2EDTA-preserved blood and unpreserved urine. Solutions (1 mg/L) of each drug in each matrix stored in aliquots (100 μL, solvents; 1.2 mL, biological samples; n = 12) at each of the three temperatures for triplicate analysis on days 3, 7, 14, and 30. On day 0 of each study, three additional aliquots of each solution were analyzed. Biological samples underwent solid-phase extraction before analysis. All samples were analyzed in full-scan by gas chromatography-mass spectrometry (GC-MS). The results of this study show that under room temperature and refrigerator storage conditions, mephedrone, naphyrone, and MDPV will degrade in methanol. This degradation starts are early as day 3. Additionally, all four drugs will degrade in Na2EDTA-preserved human whole blood samples in at least one evaluated storage environment. However, when in acetonitrile-based working solutions and unpreserved urine samples, they proved to be more stable. Methanolic working solutions and samples of Na2EDTA-preserved blood containing these cathinones should be stored in the freezer and used or tested with urgency to ensure that quantitative sample analysis is as accurate as possible in forensic casework.

Analysis of biofluids by paper spray-MS in forensic toxicology

Direct ambient ionization techniques have been developed with the aim to reduce the complexity of mass spectrometry analysis by minimizing sample preparation and chromatographic separation. In this context, paper spray-MS (PS-MS) is an innovative approach that provides faster and cheaper analysis of biofluids by the addition of the sample directly to a paper. In forensic toxicology, the analytical workflow for the detection and quantification of drugs of abuse is onerous, including sample treatment, extraction and clean up, especially regarding complex biological matrices. PS-MS allows the detection of analytes of toxicological interest in blood, plasma and urine using low sample volume. This review aims to discuss the potential use, advances and challenges of PS-MS in forensic toxicology.

Screening of 104 New Psychoactive Substances (NPS) and Other Drugs of Abuse in Oral Fluid by LC–MS-MS

New psychoactive substances (NPS) are a major public health problem, primarily due to the increased number of acute poisoning cases. Detection of these substances is a challenge. The aim of this research was to develop and validate a sensitive screening method for 104 drugs of abuse, including synthetic cannabinoids, synthetic cathinones, fentanyl analogues, phenethylamines and other abused psychoactive compounds (i.e., THC, MDMA, LSD and their metabolites) in oral fluid by liquid chromatography–tandem mass spectrometry (LC–MS-MS). The Quantisal™ oral fluid device was used to collect oral fluid samples. The oral fluid–elution buffer mixture (500-μL sample) was extracted with t-butyl methyl ether, and chromatographic separation was performed on a Raptor™ biphenyl column (100 × 2.1 mm ID, 2.7 μm), with a total run time of 13.5 min. Limits of detection were established at three concentrations (0.05, 0.1 or 1 ng/mL) for most analytes, except for acetyl norfentanyl and mescaline (5 ng/mL). Matrix effects were generally <20% and overall extraction recoveries >60%. The highest matrix effect was observed within the synthetic cannabinoid group (PB22, −55.5%). Lower recoveries were observed for 2C-T (47.2%) and JWH-175 (58.7%). Recoveries from the Quantisal™ device were also evaluated for all analytes (56.7–127%), with lower recoveries noted for 25I-NBOMe, valerylfentanyl and mCPP (56.7, 63.0 and 69.9%, respectively). Drug stability in oral fluid was evaluated at 15, 60 and 90 days and at 25, 4 and −20°C. As expected, greater stability was observed when samples were stored at −20°C, but even when frozen, some NPS (e.g., synthetic cannabinoids) showed more than 20% degradation. The method was successfully applied to the analysis of seven authentic oral fluid samples positive for 17 different analytes. The method achieved good sensitivity and simultaneous detection of a wide range of NPS.

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

The Stability of 4-Chloromethcathinone in Blood and Vitreous Humor

We present results of our study on the stability of 4-chloromethcathinone (4-CMC) in authentic postmortem peripheral blood and vitreous humor samples. The stability of 4-CMC was determined in postmortem blood samples (for a period of 90 days) and vitreous humor (30 days) at three different temperatures: -15°C, +4°C, and + 23°C. The analyses were carried out using ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). In both materials, the lowest 4-CMC stability was demonstrated at room temperature. The blood samples stored in a freezer (-15°C) showed stability for the entire study period (90 days), while in the case of the vitreous humor sample stored at the same temperature the concentration of the substance decreased by 53% after 30 days. The study carried out in authentic postmortem blood and vitreous humor samples confirms the previous reports of 4-CMC instability in biological material. Authors suggest that the biological material should be stored frozen until analyses are carried out as soon as possible after collection of the material.