An organic-reagent-free method for determination of chromium(VI) in steel alloys, sewage sludge and wastewater

One of the active areas of green chemistry research and development is in the development of new analytical methods and techniques that reduce and eliminate the use and generation of hazardous substances. In this work, a rapid and organic-regent-free method was developed for the determination of chromium(VI) by sequential injection analysis (SIA). The method was based on the detection of a blue unstable intermediate compound resulting from the reaction of Cr(VI) with hydrogen peroxide (H2O2) in acidic medium. H2O2 and its reaction products were environmentally friendly, and chromogenic reagents and organic solvents were not used in the proposed method. Different SIA parameters have been optimized and used to obtain the analytical figures of merit. Under the optimum experimental conditions, the linear range for Cr(VI) was 0.5–100.0 μg mL−1, and the detection limit was 0.16 μg mL−1. The sample throughput was 80 h−1, and the total volume of only 145 μL was consumed in each determination of Cr(VI). The method was applied for the determination of Cr(VI) in seven real samples, including alloy steel, sewage sludge and wastewater samples, and the results were compared with those obtained by atomic absorption spectrometry as well as with the certified value of Cr(VI) in standard reference material. Statistical analysis revealed that there was no significant difference at 95% confidence level.