A NEW ANALYTICAL METHOD FOR THE ASSAY OF BENZOTHIAZOLES IN HUMAN SALIVA BASED ON SOLID PHASE MICROEXTRACTION–GAS CHROMATOGRAPHY–TANDEM MASS SPECTROMETRY

Introduction

The use of BTs in a number of consumer products has resulted in increased human exposition. Their widespread use has led to ubiquitous occurrence in several environmental compartments, while a natural source of BTs has been identified in tobacco smoke. Saliva represents a valid alternative to conventional biological fluids due to its simplicity of collection, non-invasiveness, and cost-effectiveness. Trying to meet the growing demand for new analytical approaches amenable to reducing organic solvent consumption, a new protocol for the extraction of five benzothiazoles in human saliva, based on solid phase microextraction followed by gas chromatography–tandem mass spectrometry analysis (SPME-GC-MS/MS), was proposed.

Methods

Preliminary tests were conducted by comparing the headspace and immersion extraction mode. A derivatization step was tested to increase the volatility of some analytes. The SPME fiber was selected by comparing six commercially available fibers while other SPME variables were optimized with the experimental design. Method validation was conducted in accordance with the FDA guidelines.

Results

The highest extraction efficiency for all analytes investigated was obtained in immersion mode. PDMS/DVB/PDMS coating gave the best results in terms of chromatographic signal and peak asymmetry. The other SPME parameters optimized appeared to work at 40°C for 45 min, with a dilution buffer ratio of 1:1 with a saliva matrix, and a NaCl percentage of 10%. Linearity, intra- and inter-day precision, and accuracy showed satisfactory results.

Conclusions

In this work, a simple, automated, and environmentally friendly analytical method for the assessment of five BTs in human saliva was developed and validated. The use of GC coupled with triple quadrupole mass spectrometry allowed us to combine the high separation efficiency of GC with the high selectivity and sensitivity of MS/MS. A multivariate experimental design approach allowed for the simultaneous variation of multiple factors and, therefore, enabled a more comprehensive optimization process.