A Comparative Study of the Extraction Methods for the Simultaneous Detection of NPS Groups from Urine

Introduction

New psychoactive substances (NPS) has become a global issue with 134 countries and territories reporting seizures of at least one or more substances from every continent. A total of 1,127 NPS have been reported worldwide as of 2022. The increasing chemical diversity and unprecedented substance numbers of NPS make this phenomenon even more difficult to detect, monitor and understand analytically. These synthetic substances containing more than one substance, pose a global threat for public health and cause challenges for analytical chemists, toxicologists, and clinicians due to their ever-changing chemical structure. Urine as the most common used matrix for analytical toxicology studies, is an invasive biological sample and allows a longer detection time for the parent drugs and their metabolites. Considering that the NPS recovered throughout Turkey are predominantly synthetic cannabinoids and that these substances are constantly changing, it is a necessity to develop an effective extraction method for urine which covers the currently consumed synthetic cannabinoids. In view of sample extraction techniques having a noteworthy contribution to analysis results, the aim of this study was to compare the efficiency of the two most widely used techniques, liquid-liquid (LLE) and solid-phase extraction (SPE) on the detection of NPS focusing mostly on synthetic cannabinoids. In this study, the comparison of extraction techniques was performed from urine by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) system.

Methods

In order to compare the efficiency of the extraction, different LLE and SPE procedures were evaluated in terms of recovery efficiency, accuracy, and precision. A 10-point calibration was prepared in methanol. The reference standards of synthetic cannabinoids and their metabolites, synthetic cathinones, a tryptamine, and a phencyclidine-type substance were spiked at 0.5 ng/L (low) and 5 ng/L (high) levels. Each sample was analyzed in triplicate using an LC-MS/MS system equipped with an electrospray ionization source operating in positive ion mode. The selected SPE procedure was applied to 20 authentic urine samples taken from volunteers.

Results

The optimized extraction method was validated in terms of selectivity, linearity, the limit of detection, the limit of quantification, accuracy, and precision. The linear range was achieved between 0.05-5 ng/L, and correlation coefficient values of analytes were ≥0.999. Accuracy and precision studies were satisfactory for most of the substances. Results showed that the developed extraction method was suitable not only for synthetic cannabinoids but also for synthetic cathinones, tryptamine (5-MeO-Mipt) and phencyclidine type substance (ketamine) as well.

Conclusions

NPS creates societal challenges that need to be addressed greatly due to its widespread use and the speed of production-marketing-sales processes. Understanding the cultural, economic, legal and medical aspects is important for adequate health and/or policy interventions. To achieve all these, effective, simultaneous extraction techniques and analytical methods are in need as the compounds in the NPS market change. As a conclusion, the developed extraction procedure is enabled the simultaneous determination of NPS and their metabolites and also facilitates the practical monitoring of substance use for toxicologists.