Ion transfer stripping voltammetry to detect nanomolar concentrations of Cr (VI) in drinking water

Abstract

A double polymer membrane modified glass carbon electrode with poly (3-octylthiophene) (POT) was developed for trace analysis of Cr (VI) in the form of hydrogen chromate ions (HCrO4−) in an acidic solution (pH2.0). POT was electrochemically polymerized on glassy carbon (GC) electrode surfaces by cyclic voltammetry (−0.1–2.5V, 100mVs−1, four cycles). Subsequently, a 5μL plasticized poly (vinyl chloride) (PVC) was drop cast onto the POT as a second polymer, forming a double-polymer membrane. This modified electrode's stripping voltammetric current demonstrated an enhanced response to the hydrogen chromate ion, achieving a lower limit of detection of 12nM (nanomolar). Operated in the stripping voltammetric mode, this GC - POT/PVC - modified electrode had a linear current response between 30nM and 1300nM in drinking water. The electrode demonstrates good selectivity relative to ClO4− and NO3− ions; the lower limit of detection of hydrogen chromate was 20 and 16nM for ClO4− and NO3− ions, respectively. All solutions were prepared in tap water, which contains Cl−, F−, and CO32– ions at mg levels. These measurements could provide information on the lipophilicity of different toxins, leading to a better understanding of their environmental toxicity and the risks they pose to humans.