pH-resistant titania hybrid organic–inorganic coating for stir bar sorptive extraction of drugs of abuse in urine samples followed by high performance liquid chromatography–ultraviolet visible detection

An organic–inorganic hybrid titania-hydroxy-terminated silicone oil (titania-OH-TSO) stir bar coating was prepared by sol–gel method. The extraction performance of titania-OH-TSO coated stir bar was evaluated and compared with poly(dimethysiloxane) (PDMS), poly(dimethysiloxane)–divinylbenzene (PDMS–DVB), poly(dimethysiloxane)–β-cyclodextrin (PDMS–β-CD) and C18 coated stir bar with five polar drugs of abuse including amphetamine (PA), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and ketamine (Ke) as the model analytes. The experimental results revealed that the titania-OH-TSO coated stir bar exhibited highly pH-resistant ability, good preparation reproducibility, superior selectivity and high extraction efficiency for the target compounds. Based on this fact, a new method of titania-OH-TSO coated stir bar sorptive extraction (SBSE) combined with high performance liquid chromatography (HPLC)–ultraviolet visible (UV) detection was developed for the analysis of five drugs of abuse in urine samples. The factors affecting the extraction efficiency of SBSE such as sample pH, desorption solvent, sample volume, extraction time, desorption time, stirring rate and ionic strength were investigated and the optimal extraction conditions were established. Under the optimized conditions, the limits of detection (LODs) for titania-OH-TSO coated SBSE–HPLC–UV determination of five polar drugs of abuse were in the range of 2.3–9.1 μg/L with relative standard deviations (RSDs) ranging from 7.3 to 8.9% (c = 300 μg/L, n = 6), and all of the target compounds exhibited good linearity over a concentration range of 30–3000 μg/L. The developed method was applied to the determination of amphetamines and Ke in urine samples of drug abusers with satisfactory results.