Simple and rapid gas-chromatographic determination of trace amounts of lower aliphatic carbonyl compounds in exhaust gases from some odour sources

Abstract

A simple and rapid gas-liquid-solid chromatographic method for the determination of trace amounts of the lower aliphatic carbonyl compounds (C₂—C₅) in free forms in the exhaust gases from some odour sources was developed using the cold-trapping method with liquid argon. In the main analytical column the conditions were as follows: stationary phase, 1,2,3-tris-2-cyanoethoxypropane (TCEP), 5%; support, Carbopack B (60–80 mesh); glass column, 1.5 m × 3 mm i.d.; column temperature, 70 °C; carrier gas, nitrogen, flow-rate 50 ml min^–1.

In the cold-trapping pre-column the conditions were as follows: stationary phase, TCEP (25%); support, Shimalite (AW, DMCS)(60–80 mesh); glass column, 31 cm × 4 mm i.d., operating temperature for trapping, –186 °C (liquid argon); operating temperature for injection of the condensed sample into the gas chromatograph, increased from –186 °C to 120 °C in 3.5 min and maintained at this temperature for 30 s. The peaks due to lower aliphatic carbonyl compounds were identified by the disappearance method using a reaction pre-column of 2,4-dinitrophenylhydrazine (0.05 g)-orthophosphoric acid (0.1 ml) on glass beads.

The method has been applied to the determination of lower aliphatic carbonyl compounds in real samples (the exhaust gases from a poultry manure dryer, a metal paint dryer and a pig manure dryer). The volume of sample gas required is as low as about 0.41 and the method is sensitive [detection limit about 10 p.p.b. (parts per 10⁹)] and rapid (for the concentration and analysis of one sample about 30 min are required). The coefficient of variation is less than 10%. Propionaldehyde, acrolein and acetone (compounds each with three carbon atoms) were completely separated within about 7 min without tailing.