The presence of organic matter in the atmosphere is gcncrally recognized. Until quite recently, however, analytical methods for the study of such mater&& have been limited to a relatively few direct methods for individual compounds. With the development of gas chromatography, a powerful tool for the dctcction and dctermination of gaseous organic pollutants has been made available. Infrared spectroscopy has also proved very useful in some studies. Still, the identification and estimation of air-borne organic particulates remains a real problemr. However, as demonstrated by the present studies, the combination of the spot test and the ring oven techniques holds promise for solving this problem.
Although no special significance is attached to the presence of caffeine in air at this time, the fact that its presence had already been shown1 influenced its choice as the substance for initial study on the ring oven. WEST and coworkers2 have previously described the ring oven technique,as a tool for studying inorganic air-borne particulates, and the same general procedures now apply to the study of organic particles.
A number of sensitive color reactions are available for the detection of caffeine. However, most of these give similar color reactions with the other purines, the most common interferences resulting from theobromine and thcophylline. WACHSMUTH AND VAN KOECKHOVENJ obtained a reaction for caffeine with an alkaline solution of acetylacetone and an acidic solution of p-dimethylaminobcnzaldehydc in which a blue solution formed upon the addition of water. The reaction can be used for the spectrophotometric determination of caffeine and has now been adapted for use in the estimation of traces of caffeine by means of the ring oven technique. The method is free of interferences from theobromine, theophylline and other purine-containing compounds. Application to the study of air-borne organic particulates is suggested.
Solution -4 is a freshly prepared solution of 0.5 ml of acetylacctone in 5 ml of 2 N sodium hydroxide.
Solution B is a freshly prepared solution of 0.05 g of fi-dimethylaminobenzaldehyde in z ml of 12 h' hydrochloric acid. Aml. Chittt. fiCtU. 30 (1964) 227--233 228 F. ORDOVEZA, I'. W. WEST A fifiaratus Wcisx ring oven. Capillary pipets calibrated to I pl and 5 ~1. Schleichcr and Schuell analytical filter paper No. 595, 5.5 cm diameter.