Determination of Heterocyclic Tertiary Amines in Air

Abstract

A method has been developed for air sampling of two heterocyclic tertiary amines: N-methylimidazole (MI) and triethylenediamine (TEDA), which also is named 1, 4-diazabicyclo[2.2.2]octane (DABCO). Sampling of the gaseous amines was performed at three different air levels (0.5, 5, and 25 ppm) and at both 20 and 85 percent relative air humidity (RH) at each level. The amines were desorbed by solvent extraction (5% ethanol in ethyl acetate) prior to analysis by capillary gas chromatography with flame ionization (FID) or nitrogen-phosphorus detection (NPD). The gas chromatographic detection limits of the standard amines were 15 ng (FID) and 50 pg (NPD) for MI and 10 ng (FID) and 23 pg (NPD) for TEDA. The recoveries were ≥ 86 percent (20% RH) and ≥ 91 percent (85% RH) for MI and ≥ 93 percent (20% RH) and ≥83 percent (85% RH) for TEDA. Sample storage for two weeks at room temperature in darkness had no appreciable effect on recovery.

Industrial samples were collected to ascertain that no other air impurities interfered with the analysis. Samples of MI were collected at an epoxy industrial plant. The MI air levels were < 0.5 ppm. TEDA samples were collected at a polyurethane industrial plant, where the highest air level was 1 ppm. The amines in the industrial samples were determined by gas chromatography (NPD) and by gas chromatography-mass spectrometry.