Determination of N-methyl-N′-nitro-N-nitrosoguanidine in aerosol by differential pulse polarography

Abstract

The application of a sensitive electroanalytical technique for the analysis of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in aerosol was investigated. Cyclic voltammetric studies of the reduction of MNNG in acidic media showed three reduction waves. The first reduction step was assigned to be the reduction of the nitroso group and the second and third steps the reduction of the nitro group. The second peak was selected for the analysis as it was found to give a constant high current at pH below 1 and it was stable up to 40 days under normal daylight exposure and bubbling air at slow flow rate. Optimised parameters for the sensitive differential pulse polarographic technique were determined and the sampling conditions were investigated. The standard addition method was used to reduce the marix interference and the peak current was measured by the difference of current before and after UV irradiation so as to eliminate the interference caused by trace metals and electroactive and UV stable organic compounds present in air. The developed method was used to analyse MNNG aerosol in an animal room. The detection limit was found to be about 3 μg/m3 for a sampling period of 48 h with a flow rate of 100 ml/min for the scrubbing method, whereas for the membrane filter method it was about 0.1 μg/m3 for a sampling period of 8h at a flow rate of 4.9 l/min.