Electrochemical reduction and determination of Cibacron Blue F3GA at poly-l-lysine modified glassy carbon electrode

The oxidation of a reactive dye, Cibacron Blue F3GA, CB, (C.I. 61211), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode occurs in two steps at 2.0 < pH < 10 involving one electron transfer each to the amine group leading to the imide derivative. Stable films of poly-l-lysine (PLL) in the presence of glutaraldehyde (GA) 97.5%:2.5% on glassy carbon electrode can be used to detect low levels of dye using its oxidation peak at +0.75 V by voltammetry. Linear calibration graphs were obtained for the CB reactive dye, from 1.0 × 10−6 to 1.0 × 10−5 mol L−1 in B–R buffer, pH 2.0, using a pre-concentration off-line during 10 min. The detection limit (3σ/slope) was calculated to be 4.5 × 10−8 mol L−1. Films of PLL can readily be applied for the determination of CB dye bearing aminoanthraquinone as chromophore and chlorotriazinyl as reactive group at concentrations at least 100 times lesser than using a glassy carbon electrode without modification. The method described was applied for the determination of CB dye in tap water and raw water collected from the municipal treatment plant with a recovery of 89.2% ± 5.4 and 88.0% ± 6.5, respectively.