Determination of airborne carbonyls via pentafluorophenylhydrazine derivatisation by GC–MS and its comparison with HPLC method

Abstract

The classical analytical method for gaseous carbonyl measurements based on solid sorbent coated with 2,4-dinitrophenylhydrazine (DNPH) and analysis by HPLC/UV suffers from limited resolution of carbonyls with similar molecular structures and high molecular weights. In this paper, we report the development of a sensitive and reliable analytical method for simultaneous determination of 21 airborne carbonyls within the C1–C9 range. Carbonyls were collected on a sampling tube filled with 100mg Tenax TA (60–80 mesh) sorbent coated with 1μmol pentafluorophenyl hydrazine (PFPH), followed by solvent desorption and analysis by gas chromatography (GC)/mass spectrometry (MS). Common carbonyl gases including formaldehyde, acetaldehyde, butyraldehyde, hexaldehyde and benzaldehyde at ppbv levels were collected with efficiency greater than 90% onto sampling tubes at a flow rate of 100mLmin−1. The limits of detection (LODs, signal/noise=3) of the tested carbonyls were in the range of 0.08–0.20ppbv for a sampled volume of 24.0L. These limits are less than or comparable with those that can be obtained using the DNPH–HPLC method. The method has been field-tested both in ambient air of York and in diluted cigarette smoke. Comparing field tests with the classical DNPH–HPLC method, good agreement was displayed between the two methods for the same carbonyls, but with more carbonyl species detected by the PFPH–GC/MS method. The PFPH–GC/MS method provides better molecular separation for carbonyls with similar structures, is highly sensitivity and gives confirmation of identification by structures when detected using MS.