Voltammetric determination of trinitrotoluene (TNT) at antimony-modified glassy carbon paste electrode in polluted soil sample collected in an industrial area

Abstract

2,4,6-trinitrotoluene (TNT) in polluted soil sampled in the area of a factory producing industrial explosives could be determined using an antimony film pre-plated ex-situ onto a glassy carbon paste electrode (SbF-GCPE) in combination with square-wave cathodic stripping voltammetry (SWCSV). For electrochemical measurements in Britton-Robinson buffer (BRB, pH 9), the substance of interest had to be transferred from solid sample into the solution by extracting with aqueous or water / methanolic media of chosen composition and adjusted pH, in some cases, followed by neutralising the extracts with solid NaHCO3. A comparison of the results from analyses of four different solutions has allowed us to evaluate the most effective extracting agent, which was the case of a mixture of 0.5 M CH3COOH in 30% CH3OH neutralised with solid NaHCO3, and further diluted with BRB (pH 9) in order to yield pH ~ 8. In this medium, the SWCSV analysis with SbF-GCPE has resulted in the content of 3.77 μg TNT in 10 mL extract, which corresponded to the same contents in mg per 1 kg of dried soil. This has represented ca. 85% recovery with the result obtained with GC-MS, which can still be considered as acceptable agreement.