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Abstract
The emergence in recent years of potentially dangerous new psychoactive substances
(NPS) that are not under international control has led to the development of multi-analyte
procedures for their unequivocal quantification. A fast ultra-performance liquid chromatography-tandem
mass spectrometry method (UPLC-MS/MS), in combination with a sample pretreatment based
on microextraction by packed sorbent (MEPS), was for the first time used in this work
for the simultaneous determination of NPS in oral fluid. This matrix is an effective
alternative to typical biological samples for drug control in substitution therapy
programs, and also for the prevention and reduction of traffic accidents. The proposed
method allowed the separation and quantification of eleven synthetic cathinones, six
opiates, scopolamine, cocaine and two metabolites in less than 3.0min by using appropriate
isotope-labelled internal standards. The MEPS procedure, which is a miniaturized version
of the SPE technique, is completed within 15min. The influence of variables such as
the washing solution and eluent volumes, phase type, number of aspirate-dispense cycles
and pH was investigated by using a 3441//16 asymmetric screening design and a response
surface methodology based on a Doehlert design. The MEPS process performed optimally
with a mixed-mode C8/SCX sorbent and a sample pH of 9. The proposed method was validated
according to major guidelines and found to span the linear concentration range 0.5-500ngmL-1
(R2 ≥ 0.9903), and to be selective and precise (within- and between-day precision
as %RSD were both lower than 13.7%). The accuracy, in terms of analyte extraction
recovery, ranged from 75% to 125% for most of the analytes. The MEPS-UPLC-MS/MS method
was successfully used to analyse twelve real samples from patients on a drug detoxification
programme and proved an effective tool for drug monitoring.