Alkalimetric microassay of cephalosporins

Alkalimetric pH-stat titrations of cephalosporin C, cephacetril and their deacetyl derivatives using an acetyl esterase and beta-lactamase are described. The esterase was used to assay highly purified samples of cephalosporin C and cephacetril, and also to prepare analytically defined solutions of the deacetyl cephalosporins. Lactamase-catalyzed hydrolysis of the parent compounds was then found to generate exactly 2 equivalents of acid per mole; that of the deacetyl derivatives exactly 1 equivalent.