Detection of hexavalent chromium in solutions using optode membrane: fabrication and methods validation

Abstract Heavy metal pollution, such as chromium hexavalent in water, can pose a threat to human health, thus requiring a fast and efficient detection method. This research aims to build an alternative method and validate it through a cellulose triacetate (CTA)-based optode membrane that is selective for Cr(VI). The optode membrane was prepared by mixing CTA, plasticizers, aliquat 336, and selective reagents 1,5-diphenylcarbazide for Cr(VI). The optode membrane was evaluated based on validation parameters. The Cr(VI) optode membrane had average thickness of 0.028 mm, determination coefficient of 0.992 ± 0.003 at a concentration range of 0.02–0.40 mg/L, with a detection limit of 0.006 mg/L and quantitation limit of 0.017 mg/L, RSD for precision 3.03 ± 4.00 × 10 −3 %, an accuracy of 96.10 ± 5.45 %. The optode membrane exhibited good sensitivity, selectivity, and stability with sensitivity 7.8 × 10 6 M −1 cm −1 , selectivity to Fe 3+ −0.037 and Pb 2+ −0.049, stability of colour result %RSD 4.52 %. Application on water samples showed no significant difference between the results of the standard method and the optode membrane method ( α = 0.05). These results confirm that optodes can be used as an alternative method for detecting hexavalent chromium below the regulation of the WHO maximum allowable limit drinking and sanitation water.