New gas chromatographic electron-capture detection method for the determination of atmospheric aldehydes and ketones based on cartridge sampling and derivatization with 2,4,6-trichlorophenylhydrazine

The derivatizing reagent 2,4,6-trichlorophenylhydrazine (TCPH) was applied for the first time to the determination of atmospheric aldehydes and ketones using gas chromatography (GC) with electron-capture detection. TCPH is volatile enough to be used with GC without the problems of thermal decomposition or complex procedures associated with other derivatives such as 2,4-dinitrophenylhydrazine. Small cartridges packed with octadecyl silica impregnated with TCPH had collection efficiencies greater than 99% for all carbonyls tested, except for acetaldehyde and propionaldehyde which had collection efficiencies of 80 and 94%, respectively. TCPH requires only 6 min at 100 degrees C for complete reaction with low-molecular-mass carbonyls in the absence of an acid catalyst. Detection limits were determined by the blank and were 0.1 ppb (v/v) for formaldehyde in a 10-1 sample and much lower (typically 0.02-0.03 ppb, v/v) for many other carbonyls. As with other cartridge methods, a negative interference from ozone at 300 ppb (v/v) was found for the reagent and positive interferences were found for several other carbonyls. These interferences were eliminated through the use of sodium thiosulfate as an ozone scavenger.