Ultrasensitive catalytic assessment of chromium(VI) using digital imaging

Abstract

Simple, selective and highly sensitive methods of assessment of Chromium (VI) as a critical environmental pollutant are highly desirable at lower cost, especially under resource limited settings. Therefore, herein we describe for the first time the coupling of digital imaging with catalytic analysis for the extremely sensitive determination of Cr(VI) using its catalysis of the borax activated and micellar sensitized 2-aminophenol (AP) - hydrogen peroxide reaction. The fixed time kinetic measurement was applied by following the oxidation product after 10 min of mixing the reactants using a digital camera or spectrophotometrically at 435 nm. The optimized conditions were: 5 mmol L−1AP, 200 mmol L−1 H2O2, 1.1 v/v% Tween-60, 90 mmol L−1 borax, and 5 mmol L−1citrate at pH = 6.45 ± 0.05 and 45 °C. The linear calibration graph extended for up to 12.0 ng mL−1 of Cr(VI) with a detection limit (3Sb) of 0.1 ng mL−1, both by digital imaging and spectrophotometrically. The implemented method was successfully applied to various natural and polluted industrial waste waters. The analytical data were statistically in excellent agreement with those obtained following the standard GFAAS method. The developed method is two orders of magnitude more sensitive than the standard diphenylcarbazide spectrophotometric method.