Sulfonated polyvinyl chloride microparticles onto stainless-steel sheets: A cationic-exchanger planar phase for extraction of basic drugs in saliva samples.

Polymer materials are widely used as sorptive phase due to their great availability, variety and widely modification possibilities. The latter includes the introduction of different interactions between the sorbent and analytes or the enhancement of existing ones, thus increasing the extraction efficiency, selectivity, or both. This article describes a simple one-step modification of commercial polyvinyl chloride (PVC) to introduce sulfonic groups into its structure. As a result, the modified particles acquired mixed-mode sorption capacity (combination of cation-exchange and hydrophobic interactions), being confirmed by X-ray fluorescence and infrared spectroscopy. Modified PVC particles were immobilized on a stainless-steel sheet using double-sided adhesive tape, and the resulting sorptive phase was used to extract opioids (codeine, methadone, oxycodone, and tramadol) from saliva samples. During the study, key parameters affecting the extraction process (sample pH, eluent type, stirring speed, and extraction and elution times) were optimized. The procedure was combined with direct infusion tandem mass spectrometry and validated, yielding satisfactory results in terms of precision (intra-day relative standard deviation ≤ 13.4 %, inter-day relative standard deviation ≤ 9.7 %) and accuracy (intra-day relative recovery in the range of 82-111 %, inter-day relative recovery between 82 and 104 %). The scope of the developed method covers concentrations of the tested opioids found in actual saliva samples, which makes it suitable for use in drug monitoring and abuse control programs.