Quantitative determination of carbonyl compounds in rendering emissions by reversed-phase high-performance liquid chromatography of the 2,4-dinitrophenylhydrazones

Abstract

A simple and rapid method for the determination of volatile carbonyl compounds in air has been developed. The method is applied to the quantitation of C₁–C₉ aldehydes and acetone in rendering emissions.

Carbonyl compounds are sampled by absorption in a 2 × 10^–4M 2,4-dinitrophenylhydrazine solution at pH 1 and the resulting hydrazones are extracted with 2,2,4-trimethylpentane, concentrated and analysed by HPLC on a 10-µm RP-C₁₈ column with a water - acetonitrile gradient as the eluent. The hydrazones are then spectrophotometrically detected at 356 nm. The micro-scale conversion of carbonyls into 2,4-dinitrophenylhydrazones is investigated, the separation of hydrazones is improved and the sampling conditions are tested in order to achieve quantitative sampling at an air flow rate of 1 l min^–1. Quantitation is possible for concentrations as low as 15 p.p.b. (formaldehyde) and 2 p.p.b. (nonanal). The over-all coefficient of variation (taken over sampling, conversion and analyses) is less than 10%.