A Novel, Simple, and Reliable Spectrophotometric Determination of Total Hexavalent Chromium by Complexation with a New Reagent of Thiazole Linked to 2H-Chromen-2-One

Abstract

Hexavalent chromium is a known environmental contaminant and carcinogen. In the current work, a simple, rapid, and reliable direct spectrophotometric method was used for the determination of total Cr (VI) in environmental samples. Acid-base equilibria and ionization constant (pKa) of the new reagent 3-(2-(2-(4-(trifluoromethyl)benzylidene)hydrazineyl) thiazol-4-yl)-2H-chromen-2-one (thiazole linked to 2H-chromen-2-one, TFZ) were investigated. The value of pKa for the reagent was found to be 7.6 which was initially reported. The reaction of the TFZ ligand with Cr (VI) was optimized to produce a highly absorbent complex at 370 nm and pH 7.0 within 1 min. With a correlation coefficient of 0.9994, the linear concentration range ranges from 2 to 20,000 ng·mL−1. The detection limit and quantification limit were 0.73 and 2.43 ng·mL−1, respectively. The method has high precision with relative standard deviations less than 1.0 and high accuracy with recovery of 100 ± 2%. A large excess of cations and anions did not interfere with the determination of Cr (VI). The proposed method was successfully applied to the determination of Cr (VI) in cement samples. The current method could be useful for the routine analysis of Cr (VI) in environmental labs.