Monolith-coated microcentrifuge tubes for the easy extraction of psychoactive substances from urine samples and liquid chromatography-tandem mass spectrometry determination.

BACKGROUND: Sample extraction is one of the most critical steps in most of the analytical processes. Nowadays, there is a demand for simple approaches that can effectively extract and concentrate target analytes from complex matrices, like biofluids, with accurate and reliable results. RESULTS: A porous monolith of poly(methacrylic acid-co-ethylene glycol dimethacrylate) has been immobilized on the inner wall of a 2 mL commercial polypropylene microcentrifuge tube through radical photopolymerization, using bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as radical initiator and 405 nm laser pointer activation. Photopolymerization parameters were adjusted to obtain a continuous and homogeneous polymer layer (0.16 mm wet polymer thickness and 31 mg dry polymer weight) in the inner tube surface. Extraction efficiency of twelve psychoactive substances was assessed by the evaluation of the effect of sample pH, extraction and desorption times, and desorption solvent volume. Moreover, matrix effect, reusability and stability of monolith-coated microcentrifuge tubes were studied. Sample extracts were measured by liquid chromatography-tandem mass spectrometry, providing limits of quantification (LOQ) from 0.2 to 2.7 µg L-1, recoveries from 80 to 118 %, relative standard deviations lower than 17 %, and a linear range from LOQ to 500 µg L-1. SIGNIFICANCE: The proposed device is suitable for the easy and simple extraction of psychoactive substances from urine samples with a high portability, reduced solvent consumption, low cost, and low environmental impact.

Development of paper-immobilized molecularly imprinted polymers by laser pointer activation for methamphetamine extraction with analysis by ion mobility spectrometry.

A fast, simple, cheap, and versatile strategy has been proposed for the synthesis of paper-immobilized molecularly imprinted polymers (MIPs) by photoactivated bulk polymerization over a piece of nitrocellulose using a 405 nm laser pointer. Polymerization was carried out using a mixture of methacrylic acid and ethylene glycol dimethacrylate, using methamphetamine as template molecule and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as radical initiator. After investigation of different polymerization parameters, the following experimental conditions were found to give best results: size of nitrocellulose strip (13.5 × 4.0 × 0.8 mm), type of porogen (acetonitrile), polymerization mixture volume (75 µL), and irradiation times (10 min). Experimental conditions (such as sample pH, extraction and desorption time, and type and volume of desorption solvent) were also adjusted for the extraction of methamphetamine using the proposed paper-MIP. Methamphetamine determination was carried out by ion mobility spectrometry providing a limit of detection of 14 µg L-1 and quantitative recoveries from 81 to 95% using spiked urine and oral fluid samples. The proposed paper-immobilized MIP device allows a simple and selective sample extraction procedure for the determination of methamphetamine in oral fluids and urine with a high portability, minimal solvent consumption, and reduced costs compared to other conventional approaches.

Paper-based monolith extraction of psychoactive substances from biological fluids.

A monolith of poly(methacrylic acid-co-ethylene glycol dimethacrylate) has been immobilised to a nitrocellulose strip by radical photopolymerisation to be used in the extraction of psychoactive substances in biological fluids. Codeine, methylone, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, butylone, norketamine, ketamine, heroin, cocaine, lysergic acid diethylamide and fentanyl were employed as model drugs and final extracts were analysed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Polymerisation parameters were adjusted in order to obtain a stable and homogeneous layer of monolith onto the nitrocellulose strip. The resulting sorptive phase was characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Extraction conditions were investigated by the evaluation of sample pH, extraction and desorption times and desorption solvent volume, providing enrichment factor values ranging from 5.3 to 39.9. The proposed methodology provided limit of quantification values from 0.013 µg L-1 for methylone to 0.057 µg L-1 for amphetamine, and recoveries from 64 to 120%. Urine and serum certified reference materials were employed in the validation of the proposed methodology, providing results statistically comparable. The developed approach is simple and straightforward for the determination of psychoactive substances in urine and serum samples.