A High-throughput Novel Approach for the Determination of Cresols in Wastewater Based on Stir Bar Sorptive Extraction Along with Thermal Desorption GC-MS/MS

In this study, stir bar sorptive extraction as an easy to use, solventless, and novel sample enrichment technique combined with thermal desorption (TD)-gas chromatography triple quadrupole mass spectrometry (GC-MS/MS) was applied to determine cresols in wastewater samples for the first time. The analytical method is based on effortless extraction followed by TD-GC-MS/MS detection not requiring derivatization. The design of experiment procedure was utilized for improved extraction and analytical conditions. In this regard, the major sample extraction parameters (extraction time, salt addition, methanol content, pH, and stirring rate) and TD parameters (desorption flow, desorption temperature, desorption time, and cryo-focusing inlet temperature) were scrutinized and optimized. The fractional factorial design showed that stirring rate, extraction time, and methanol content were the major influential factors for extraction. While desorption flow, desorption temperature, and cryo-focusing inlet temperature significantly affected the instrumental analysis conditions. The optimized methodological conditions for the stir bar coated with polydimethylsiloxane were as follows: sample volume of 20 mL, methanol addition of 10%, stirring rate of 1200 rpm, desorption time of 10 min, desorption temperature of 240 degrees C, desorption flow of 20 mL/min, and cryo-focusing inlet temperature of -20 degrees C. The analytical characteristic of the proposed methodology presents good linearity (0.9909-0.9918), repeatability (11.5-15.1%), recovery (104.78 +/- 0.27 to 106.19 +/- 0.16%), and low detection limits (0.020-0.04 ng/mL). The established method was employed to measure trace levels of cresols in several wastewater samples taken from Istanbul.