Environ. Sci. Technol. lQQ3,27, 2745-2753
Identification of Carbonyl Compounds in Environmental Samples Richard M. Le Lacheur,'vt Lucinda B. Sonnenberg? Philip C. Slnger,t Russell F. Christman: and M. Judith Charles?
Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7400,and Institute of Paper Science and Technology, 500 10th Street NW, Atlanta, Georgia 30318-5794 ~~
Carbonyl compounds play an important role in many environmental oxidation processes, but the identification of unknown carbonyl compounds can be difficult using existingtechniques. We have developed an approach using derivatization with 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) followed by gas chromatography/mass spectrometry (GUMS) analysis for the identification of unknown carbonyl compounds. Electron ionization, electron-capture negative chemical ionization, and positive chemical ionization mass spectrometry have all been examined using model compounds. Methods for identifying molecular weight are described, as well as methods for differentiating between different types of carbonyl compounds. GC/MS analysis of compounds containing carboxylic acid or hydroxyl groups in addition to the carbonyl group can be conducted by using PFBHA derivatization in conjugation with methylation and silylation. Electron ionization mass spectrometric analysis of the derivatives will usually provide for adequate molecular weight and structural information. The methods developed are demonstrated for three different types of samples.
that the identity of the molecule is known and that a standard exists. In practice, the mass spectra of the PFBHA derivatives frequently do not provide adequate information for the determination of molecular weight or of compound structure (5, 6). We report here an approach for the identification of single and polyfunctional carbonyl-containing compounds. The approach is based on derivatization with PFBHA and subsequent derivatization with methylating or silylating reagents for the polyfunctional compounds. Mass spectrometric analyses using electron ionization, positive chemical ionization, and electron-capture negative chemical ionization were evaluated. Experimental Section
I. Model Compound Studies. Model compounds (Table I) were chosen for their relevance to aquatic and atmospheric systems and for structural variety. Saturated aldehydes and ketones (group I) have been shown to be major byproducts in the ozonation of water (5-81, and unsaturated carbonyl compounds may be formed during the photooxidation of isoprene (11, 12). The polyfunctional compounds (group 11) are models of potential byproducts of the oxidation processes in atmospheric and aquatic systems and include compounds with hydroxy and Introduction carbonyl groups and compounds with carboxylic acid and Carbonyl compounds have been implicated as mutagens carbonyl groups. and possible carcinogens (1, 2) and may comprise a 11. Derivatization of Model Compounds. A. Oxime significant portion of the organic carbon balance in both Formation and Extraction. The model compounds aquatic and atmospheric oxidation processes. For examlisted in Table I were derivatized in deionized, distilled ple, the carbonyl compounds formaldehyde, acetaldehyde, water with 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine glyoxal, and methylglyoxal are major byproducts in the hydrochloride (PFBHA, Aldrich Chemical Co, Milwaukee, ozonation of natural waters (3-8),and the polyfunctional WI). The concentration of the model compounds varied carbonyl compounds Z-2-chloro-3-(dichloromethyl)-4-oxfrom 100 to 10000pg/L. A 10-mL aliquot of the water was obutenoic acid (MX) and E-2-chloro-3-(dichloromethyl)taken, and 5-10 drops of a 1M solution of pH 7 phosphate 4-oxobutenoic acid (EMX) have been found to be responbuffer was added. A minimum 10-fold molar excess of sible for 35% of the mutagenic activity in a chloraminated PFBHA was added to the water to enhance derivatization fulvic acid extract (9) and for up to 40% of the mutagenic yields, and the mixture was allowed to react at room activity in a chlorinated fulvic acid extract (10). In temperature for 24 h. Concentrated HC1 was then added atmospheric systems, carbonyl compounds may account to the aqueous solution until a pH
