Determination of aldehydes and ketones in ambient air by micellar electrokinetic capillary chromatography

Abstract

A new analytical method was developed for determining 14 aldehydes and ketones of environmental interest in ambient air. The method uses 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges for sampling, acetonitrile for preconcentration, and micellar electrokinetic capillary chromatography for separation and quantitation. With hydrodynamic sampling of 8.5 cm cartridge for 30 s, applied voltage of 25 kV, detection at 360 nm, and separation in a 60 cm long, 50 μm id fused silica column at ambient temperature (25° ± 1 °C) within an electrophoretic buffer (20 mM borate/50 mM sodium dodecyl sulfate at pH 9.2 in 20% [v/v] methanol), baseline separation was obtained for DNPH derivatives of formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, butanone, crotonaldehyde, isobutyraldehyde/butyraldehyde, 2-pentenaldehyde, isovaleraldehyde, valeraldehyde, benzaldehyde, and hexaldehyde. Detection limits [signal-to-noise (S/N) ratio = 2] ranged from 0.10 to 0.77 mg/L, the working range was 0.3-86 mg/L, and the precision as indicated by the relative standard deviation ranged from 2.3 to 6.6% (n = 3). With 1 h sampling at 0.25 L/min and a 1000-fold enrichment, most carbonyl compounds in ambient air can be determined with detection limits ranging from 0.008 to 0.1 mg/m3 and a working range of 0.04-11 μg/m3. The developed method was successfully applied to the determination of carbonyl compounds in a chemical laboratory and at street level.