Determination of aldehydes in air and water by the PFBHA solid sorbent method.

摘要

Low molecular weight aldehydes have been serious concerns because of their ubiquitous occurrence and the fact that such aldehydes are regarded as carcinogenic to animals, especially formaldehyde, acetaldehyde, crotonaldehyde, and furfural. OSHA considers the low molecular weight aldehydes as potential occupational carcinogens. The aldehydes are also irritants to the mucous membranes. The US Environmental Protection Agency is still developing regulations for disinfection by-products (DBPs) in its Drinking Water Act amendments. Because of the high vapor pressure, aldehydes not only exist in water but also in air. The aim of this study was to use O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) as a derivatizing reagent with solid phase sorbents to develop efficient, fast, and accurate methods to concentrate the aldehydes and ketones in the air and the water. The selected straight chain aldehydes were from C1 to C10 plus glyoxal and methylglyoxal found in ozonated drinking water. The syntheses of the PFBHA O-oximes were accomplished with >80% yield for all. The O-Oximes were utilized to generate internal standard curves for each aldehyde and mixture to obtain gas chromatography/electron capture detector analysis conditions to resolve all 12 derivatives. The instrumental detection limit ranged from 0.4 to 1 ppb aldehyde in 20 ml water. Initial work revealed high concentrations of C1 and C2 aldehydes in Millipore distilled water which led to an investigation to minimize the aldehyde background. The optimum two treatments (42% removal efficiency of C1) were acid KMnO4 distillation under nitrogen, and an acid conditioning anion exchange method, with the acid KMnO4 distillation being more precise (CV, 9.5%). This allowed reagent solutions to be prepared with minimum background. Three liquid-liquid extraction (LLE) methods (ultrasonication, microwave, reference EPA) were compared with three solid sorbent methods (cation exchange; C18; C18+ PFBHA coated sorbents) for aldehyde concentrations from 10 ppb to 1000 ppb (w/v). The best method relative to aldehyde and recovery criteria was the microwave method. Air sampling with 10% (w/w) PFBBHA coated Tenax TA (80/100 mesh) was shown to be quantitative down to 500 ppb (v/v) of aldehydes in air, with adequate recovery down to 25 ppb (v/v) for some aldehydes. Passive sampling was also shown to be possible to the low ppb (v/v) level with efficiencies relative to calculated diffusion coefficients being variable with aldehyde. Thus the practical lower limits for the water and air sampling methods were defined by these studies for use in environmental studies.