Voltammetric Determination of Selected Nitro Compounds at a Polished Silver Solid Amalgam Composite Electrode

Voltammetric behavior of selected biologically active organic nitro compounds, namely 2-nitrofluorene, picric acid (2,4,6-trinitrophenol) and metronidazole, has been investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a polished silver solid amalgam composite electrode (p-AgSA-CE). The optimum conditions have been found for their determination in a 1:1 mixture of methanol and aqueous Britton-Robinson buffer of pH 5.0 for 2-nitrofluorene and in the aqueous Britton-Robinson buffer solutions of pH 2.0 and 4.0 for picric acid and metronidazole, respectively, with the limits of quantification (L(Q)s) 4, 0.1 and 2 mu molL(-1) (DCV at p-AgSA-CE) and 3, 1 and 4 mu molL(-1) (DPV at p-AgSA-CE) for 2-nitrofluorene, picric acid and metronidazole, respectively. An attempt to increase the sensitivity using adsorptive stripping voltammetry was not successful for all three test substances. For comparison, the UV-vis spectrophotometric determinations of studied compounds have also been carried out in methanol for 2-nitrofluorene (L-Q approximate to 1 mu molL(-1)) and in deionized water for picric acid (L-Q approximate to 3 mu molL(-1)) and metronidazole (L-Q approximate to 2 mu molL(-1)). Practical applicability of the newly developed voltammetric methods was verified on direct determination of the studied compounds in drinking and river waters with L(Q)s around 10(-6) molL(-1) for all the studied compounds.