Field Evaluation of N-Methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) Coated Silica Gel Cartridges for the Measurement of Lower Carbonyls in Air

Abstract

Formaldehyde, acetaldehyde and acetone were measured in ambient air after they were simultaneously collected at 0.8 L min⁻¹ on two parallel silica gel cartridges coated with 2,4-dinitrophenylhydrazine (DNPH) and N-methyl-4-hydrazino-2-nitrobenzofurazan (MNBDH), respectively. By reaction with the two reagents, the three carbonyls were derivatized to the corresponding hydrazones, which were then separated, identified and quantified by HPLC with UV/visible detection. The limits of detection for HCHO, CH₃CHO and CH₃COCH₃ ranged between 0.14 and 0.29 ppbv for 100 L (2h) air sampled on MNBDH-coated cartridges. The comparison between the two chromatographic methods under field sampling conditions showed that only HCHO appeared to have been collected on MNBDH cartridges, whilst CH₃CHO and CH₃COCH₃ were almost completely lost. Moreover, a not very satisfactory consistency between the HCHO mixing ratios provided by the two types of cartridges (R²=0.57) was observed.