Voltammetric determination of 2-nitrobiphenyl and 4-nitrobiphenyl using a mercury meniscus modified silver solid amalgam electrode

Direct current voltammetry (DCV), differential pulse voltammetry (DPV), and differential pulse adsorptive stripping voltammetry (DPAdSV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) were used for the determination of trace amounts of carcinogenic 2-nitrobiphenyl (2-NBP) and 4-nitrobiphenyl (4-NBP) in buffered aqueous-methanolic solutions (for 2-NBP: 0.01 mol L^-1 LiOH (pH 12.0) - methanol (9:1), for 4-NBP: 0.25 mol L^-1 acetate buffer (AB) of pH 4.8-methanol (7:3)). Both nitrobiphenyls (NBPs) can be determined by DCV and DPV in the concentration range 0.2-100 μmol L^-1 (limit of quantification (LQ) of both NBPs for DCV is 0.2 μmol L^-1, LQ of 2-NBP and 4-NBP for DPV is 0.1 and 0.2 μmol L^-1, respectively). An attempt to decrease the LQ using DPAdSV was not successful, probably due to some competitive adsorption. The optimal medium for the simultaneous determination of 2-NBP and 4-NBP by DPV at the m-AgSAE was: 0.10 mol L^-1 AB of pH 6.0-methanol (7:3). The dependences of the peak current on the concentration of individual NBPs in the mixture were linear in the 10^-6 and 10^-7 mol L^-1 concentration ranges. The practical applicability of the newly developed methods was verified using model samples of drinking and river water.