Speciation of chromium in water samples and lettuce extracts in the unified bioaccessibility method (UBM) saliva solution by vortex assisted-dispersive solid phase microextraction

In this study, a new sulfonamide based polymeric adsorbent (5ATT-CSPS) was prepared with reaction between 5-Amino-1,3,4-thiadiazole-2-thiol and chlorosulfonated polystyrene resin and characterized by FT-IR, FESEM-EDX, XPS, zeta potential. It was used for the first time as an adsorbent for speciation of chromium in various water samples and lettuce extracts in UBM saliva by dispersive solid phase micro extraction (D-SPµE). The total chromium concentration was determined by F AAS. The parameters affecting the recovery of Cr(III) such as pH, contact times, elution conditions, sample volume, co-existing ions and adsorption capacity were optimized. The adsorbent demonstrated a good performance for adsorption of Cr(III) (R%≥95). It was quantitatively adsorbed in the range of pH 2.0–4.0 whereas Cr(VI) was not adsorbed in the pH range of 2.0–8.0. Therefore Cr(VI) concentration was calculated indirectly. The elution was achieved by 5 mL of 2 mol L⁻¹ HNO₃. Adsorption and elution contact times of the adsorbent were 3 min and 2 min, respectively. The preconcentration factor of the method was found to be 8. Considering optimal conditions, limit of detection was found to be 2.9 µg L⁻¹, and precision of the method (as RSD%) was found to be ≤ 4.3%. The adsorption capacity of the 5ATT-CSPS for Cr(III) was 25 mg g⁻¹. The accuracy of this method was verified by analyzing TMDA-70 certified reference material and by recovery studies in spiked water samples and lettuce extracts in the unified bioaccessibility method (UBM) saliva.