Development of a Dispersive Liquid-Liquid Microextraction for Synthetic Cathinones in Biological Fluids Based on Principles of Green Analytical Toxicology.

Abstract

The present work describes a practical application of Green Analytical Toxicology (GAT) during the development of an eco-friendly dispersive liquid-liquid microextraction (DLLME) avoiding the use of highly toxic chlorinated solvents that are commonly used in this type of the technique. The purpose was to further consolidate GAT guidelines during method development. Thus, a full method optimization using a multivariate statistical approach and validation were performed. To that end, synthetic cathinones (SCs), one of the major classes of new psychoactive substances, were the target analytes due to their relevance and chemical diversity. Furthermore, whole blood and urine samples were the matrices of choice due to their clinical relevance. The sample preparation step prior to DLLME consisted of protein precipitation of whole blood samples, while urine specimens were centrifuged and diluted with ultrapure water. Then, borate buffer, sodium chloride and ethyl acetate:acetonitrile were added and vortexed. Finally, vials were centrifuged and the organic layer was transferred to autosampler vials, evaporated to dryness and resuspended with mobile phase prior to injection into the ultra-high performance liquid chromatography-tandem mass spectrometry system. Once optimized, the proposed DLLME was fully validated: 0.2 and 1 ng/mL as the limit of detection and 1 and 10 ng/mL as the limit of quantitation for urine and blood samples, respectively. The linear range was established as 1-100 and 10-1,000 ng/mL for urine and blood samples, respectively (r2 > 0.99), while the bias and precision were within acceptable limits (≥80%). The matrix effect was of 1.9-260.2% and -12.3-139.6%; while the recovery was of 27.4-60.0% and 13.0-55.2%; the process efficiency ranged from 45.0% to 192.0% and 17.9% to 58.4% for whole blood and urine, respectively. Finally, the method was applied to real case samples as proof of applicability. Thus, a simple, cheap and fast eco-friendly technique to analyze SCs in two biological specimens was described.