Penicillin in Broths and Finished Products

Abstract

ence between the corrected lines. Thus, by the ferricyanide method, it is permissible to determine procaine penicillin as penicillin and divide the results by 2 if an aliquot containing approsimately 1 mg. of procaine penicillin is used.Results of the analysis of procaine penicillin by this method are compared in Table I1 nith results by the bioassay and iodometric methods. The mean difference between the bioassay and ferricyanide methods is 37 units, and between the bioassay arid iodometric methods it is 239 units. It is obvious that the ferricyanide method can be used for the analysis of procaine penicillins only while they retain their full potency. If a loss in potency is suspected, the compound should be analyzed before and after the addition of penicillinase. The penicillinase prepared in this laboratory ( 2 ) does not interfere with the determination nor affect procaine. Although penicillinase destroys completely the biological activity of penicillin, it does not destroy all its chemical activity as measured by the ferricyanide method. The loss in activity varies with the conditions under which the penicillinase acts but is relatively constant under given conditions. Once this loss has been determined for the given conditions, the difference in the ferricyanide assay before and after the action of penicillinase will give a good estimate of the potency. CONCLUSIOhSThe ferricyanide method possesses several advantages. I t is rapid; determinations require less than 30 minutes. I t is sensitive, using less than 1 mg. of penicillin per determination. I t is simple and needs only a minimum of standard equipment. The number of standard reagents necessary is reduced to one which is stable.The chief disadvantage of the method is that it may be applied only to crystalline penicillin. Many penicillin preparations contain substances that interfere with the procedure. 4CKIOWLEDGMENTSGifts of crystalline sodium penicillin G were received from Merck & Company of Montreal, and Ayerst, McKenna and Harrison of Montreal.Bioassays were carried out under the direction of Ruth Thomas. Frances Connell made the iodometric determinations. LITERATURE CITED(1) Alicino,

Determination of Phenylacetic Acid and Phenylacetamides in Samples from Penicillin Fermentations

“…The first attempt in the present study consisted of a search for a convenient method for the determination of penicilloic acid. The iodometric titration (1) or the alkaline reduction of ferricyanide (S, 9) can obviously serve this purpose. However, the titration method is as a rule not as sensitive and simple as many colorimetric procedures while the reduction of ferricyanide is not considered specific enough for samples from penicillin fermentations.…”

Chromatography

“…An increasing number of examples shows that many combinations of solvents and absorbents may be employed for resolution of one kind of solute-for example, mixtures of organic acids may be resolved by absorption in columns of ion exchangers with water or with organic liquids as solvents, a variation that may lead to inversion of the adsorption sequence (107). They may be separated in columns of silica gel with chloroform or iso-octane as solvent (50,103), in columns of Celite plus strong sulfuric acid and with benzene or butanol as solvent (55,94), in columns of charcoal with various solvents (56), in columns of alumina with various solvents (37,69,186), and in paper with water, aqueous phenol, or butanol as solvent (21,79).…”

“…Mixtures of various lower fatty acids have been resolved in columns of siliceous earth impregnated with methanol (103), with strong sulfuric acid (94), and with strong sulfuric acid plus phosphoric acid (55). Silica columns have also been employed for isolation of radioactive citric acid (101).…”