Cotton fibers functionalized with β-cyclodextrins as selectivity enhancer for the direct infusion mass spectrometric determination of cocaine and methamphetamine in saliva samples.

Cotton is a natural material with good mechanical and chemical properties. It presents a hydrophilic surface that must be modified by the introduction of appropriate groups, if semi-polar or non-polar analytes are intended to be isolated from an aqueous matrix. In this article, cotton is modified with β-cyclodextrins, which presents a hydrophobic cavity where target molecules can be hosted. The cavity size restricts the access of larger or less accessible molecules due to their conformation, thus improving the extraction selectivity. The modified cotton fibers are packed in a disposable syringe device where all the steps of the extraction take place. The ensuing fibers were evaluated for the extraction of several drugs providing the best results for cocaine (CO) and methamphetamine (MTA). These targets were extracted from saliva samples and finally determined by direct infusion mass spectrometry. The method provides limits of detection and quantification of 0.6 and 2 μg L-1 for CO and 0.8 and 2.7 μg L-1 for MTA, with precision values at the quantification level better than the 9% (expressed as relative standard deviation). Also, relative recoveries ranged from 115% to 111% for CO and MTA, respectively, demonstrating the applicability of the proposed method. Matrix effect, which has been statistically evaluated, is not significant, showing that the extraction selectivity can compensate the circumvent of the chromatographic separation.