A highly sensitive colorimetric assessment of hexavalent chromium using a digital camera
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A highly sensitive colorimetric assessment of hexavalent chromium using a digital camera Ashraf A. Mohamed
&
Ethar M. Ismail
&
Samah Ali
Received: 13 May 2020 / Accepted: 16 September 2020 # Springer Nature Switzerland AG 2020
Abstract Simple, low-cost, and sensitive methods for the assessment of hexavalent chromium as an important environmental pollutant are highly desirable, especially under resource-limited settings. Therefore, herein we propose an original approach for the simple, low-cost, selective, and extremely sensitive assessment of Cr(VI) utilizing its catalysis of the micellar sensitized o-dianisidine (DA)–hydrogen peroxide reaction. The initial rate of the amended reaction is monitored by tracing the oxidation product, either by a digital camera video recording or spectrophotometrically at 440 nm, for 120 s from mixing the reactants. The optimized reaction conditions were 5 mmol L−1 DA, 0.6 mol L−1 H2O2, 2.0 v/v% Tween 20, and 10 mmol L−1 chloroacetate buffer (pH 4.5 ± 0.1), at 30 °C. The linear calibration graph extends to 90.0 ng mL−1 Cr(VI) with detection limits (3Sb) of 0.8 and 1.0 ng mL−1, for the video recording and spectrophotometric procedures, A. A. Mohamed (*) : E. M. Ismail Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo 11566, Egypt e-mail: [email protected]
E. M. Ismail e-mail: [email protected] S. Ali Chemistry Department, Faculty of Science, Taibah University, Al-Madinah, Saudi Arabia e-mail: [email protected] S. Ali The National Organization for Drug Control and Research, Al-Agouzah, Giza, Egypt
respectively. The amended method was successfully applied to the assessment of Cr(IV) in natural and polluted industrial wastewaters. The analytical data were in excellent statistical harmony with those of the standard ETAAS method. The proposed method is two orders of magnitude more sensitive than the diphenylcarbazide standard spectrophotometric method.
Keywords Digital camera sensing . Video recording . Catalytic determination of Cr(VI) . Dianisidine– hydrogen peroxide reaction . Natural and wastewaters
Introduction There are two settled oxidation states for chromium: the trivalent that is important for human, as a micronutrient, and the hexavalent that is highly toxic (ATSDR 2012). According to the International Agency for Research on Cancer (IARC), Cr(VI) is categorized under group one carcinogens for humans so that the WHO guidelines for drinking water quality specified a maximum contaminant level (MCL) of 50 ng mL−1 Cr(VI) (ATSDR 2012). Therefore, the development of low-cost and precise methods for the highly sensitive assessment of Cr(VI) is very important for environmental, chemical, and health concerns. Popular methods for the assessment of ultra-trace amounts of Cr(VI) include flame atomic absorption spectrometry (FAAS) (Islam et al. 2015; Zhan et al. 2019; Sharma et al. 2017), electrothermal atomic absorption spectrometry (ETAAS) (Nafti et al.
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2019; Procházková et al. 2019; Kazi et al. 2019; Yao et al. 20
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