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a two-pen recorder allows t h e two responses t o b e ratioed, t h u s adding confidence to t h e qualitative d e t e r m i nation. T h r e e to five p p b by volume of VCM can confidently be detected with this analytical scheme when only 300 cc of air is sampled. T h e sample t u b e s are versatile enough to be used for t h e concentration of a variety of c o m p o u n d s . Caution should be exercised if t h e t u b e s are to be used for collection of benzene or toluene, because h e a t desorbing of T e n a x routinely results in peaks a t t h e retention times of those c o m p o u n d s . Some investigators have developed rigorous clean-up procedures which prevent this problem (8, 9). T h e r e are m a n y examples of a mult i i n s t r u m e n t a p p r o a c h t o analysis of samples. Our laboratory was involved in sampling a n d analyzing for nitrobenzene, which was suspected of originating from waste oils t h a t h a d been applied to public roads in several communities. Originally, water samples from t h e ditches of the affected area were s u b m i t t e d . T h e s e were r a t h e r dirty a n d could n o t be directly analyzed by G C / M S without clean-up a n d concentration. High pressure liquid c h r o m a t o g r a p h y was employed t o hasten t h e d e t e r m i n a t i o n of nitrobenzene's presence. G C / M S was t h e n used for confirmation of the suspected

peak. After determining t h a t nitrobenzene was indeed p r e s e n t in t h e runoff, t r u e a m b i e n t air samples were obtained by absorption in ethylene glycol a n d by using t h e previously described concentration t u b e s with s u b sequent GC analysis. H P L C became the t e c h n i q u e of choice for t h e analysis of these samples because of the simplicity of the analytical scheme. Monitoring continued until t h e oil h a d been removed from t h e area. T h e complexity of a m b i e n t air samples often requires a m u l t i i n s t r u m e n tal a p p r o a c h if t h e sample is t o be qualitatively a n d quantitatively analyzed so t h a t t h e information can be used for corrective action or t o identify potential problems of air pollution. Competency in staff proficiency m u s t be m a i n t a i n e d , a n d sophisticated ins t r u m e n t a t i o n m u s t be available. T h e need for effective a n d efficient sample concentration techniques c a n n o t be overlooked. It is a n area which needs to be pursued, a n d advantages a n d limitations of a particular procedure should be identified before it is routinely used for t h e collection a n d conc e n t r a t i o n of a m b i e n t air contaminants.

Acknowledgment T h e generous s u p p o r t of the Texas Air Control Board a n d t h e contribu-

tions a n d assistance provided by our staff a n d a d m i n i s t r a t i o n in t h e preparation of this presentation are gratefully acknowledged.

References (1) J. R. Rhodes, Am. Lab., (7), 57 (1973). (2) J. R. Rhodes, A. H. Pradzynski, C. B. Hunter, J. S. Payne, and J. L. Lindgren, Environ. Sci. and TechnoL, 6 (10), 922 (1972). (3) J. S. Mgebroff and J. S. Payne, "The Determination of Trace Elements in Fuel Oil by Energy Dispersive X-ray Fluorescence Analysis," presented at the 29th Annual Meeting of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. (4) J. L. Lindgren, H. J. Krauss, and J. S. Payne, "Determination of Pesticides in Environmental Samples: Substituting HPLC for GC," presented at the 30th Annual Meeting of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. (5) J. L. Lindgren, H. J. Krauss, and M. A. Fox, Journal of the Air Pollution Control Association, 30 (2), 166 (1980). (6) W. Bertsch, R. C. Chang, and A. Zlatkis, J. Chromatogr. Sci., 12 (4) 175 (1974). (7) J. L. Lindgren and G. Speller, "Determination of Vinyl Chloride Monomer in the Ambient Air Near Point Source Emissions," presented at the 30th Annual Meeting of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. (8) E. D. Pelizzari, private communication. (9) L. T. Freeland, private communication.

PHENOLS AND AROMATIC AMINES? We're the specialists in liquid c h r o m a t o g raphy for trace organic determinations. Let us know your problem. We will provide detailed applications support and a selection of instrumentation which will do your job in the most cost effective manner. LC systems based on ultraviolet a n d / o r electrochemical detection are tailor made for environmental analysis. Temperature control, gradient elution, automated trace enrichment, and column switching are options which may be adapted to your needs. Circle the bingo card for general information, but if you want specific answers, write to our Environmental Services Department and tell them what y o u can about your samples.

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1078 A · ANALYTICAL CHEMISTRY, VOL. 52, NO. 9, AUGUST 1980