Utilizing the amphoteric nature of most sulfonamides, a simple extraction method followed by the colorimetric development, based on the diazotization-coupling reaction with N-(l-naphthyl) ethylenediamine dihydrochloride, is described for the determination of sulfonamides alone and in combination with procaine penicillin G in milk. Recoveries for the ten sulfonamides studied ranged from 81 to 100% recovery at the 100-p.p.b. level.

Previous studies o n the degradation of barbiturates have indicated that the products of hydrolysis of the ionic and nonionic forms might be different. During the course of a study o n the analysis of phenobarbital it was discovered that one of the postulated products (phenylethylacetylurea) could be determined in the presence of phenobarbital. Experiments were therefore undertaken to follow the breakdown of phenobarbital and the ureide at different p H values. The pseudo first-order rate constants for phenobarbital and the ureide were then determined. Analysis of equilibria phenomena and series first-order reaction kinetics show that the fraction decomposing by the ureide path is dependent o n the concentration of the ionic form as previously postulated. REVIOUS WORK on the degradation of barbit-Purates (1) EXPERIMENTALReagents and Apparatus.-Phenobarbital, U.S.P. grade was recrystallized from dilute ethanol, m.p. 176-178'. Phenylethylacetylurea was prepared by thermal degradation of a 5% aqueous solution of phenobarbital and isolation of the precipitate. The ureide was recrystallized from dilute ethanol, m.p. 147-149" (3-5).Ammonia buffer solutions (0.2, 0.4, 0.6, and 0.8 total molarity NH3 and NHa+) a t pH values of 8.0, 8.5, 9.0, and 0.8 M a t a pH of 8.2, 8.7, and 9.5 were used. The total ionic strength was adjusted to 1.0 with potassium chloride in each case. A Beckman model DU spectrophotometer and a Beckman zeromatic pH meter were used.Assays.-The concentration of phenobarbital was followed by determining the change in absorbance at 241 mp in the following manner: a 10-ml. sample was diluted to 100 ml. with ammonia buffer (pH

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The fluorescent property of metoserpate after reaction with nitrous acid is utilized for its determination in biological systems. The procedure can easily detect 5 p.p.b. of drug. A general procedure is given for tissues (kidney, liver, muscle, and fat) which is applicable with slight modifications to eggs and blood. Average recoveries were greater than 64% in fat and greater than 74% in all other biological systems. The average controls gave an apparent metoserpate concentration of 0 p.p.b. for eggs, 2 p.p.b. for blood, while the highest average control from tissue was 2 p.p.b.