Use of Charge-Transfer Complexation in the Spectro-photometric and Spectrodensitometric Analysis of Cephalothin Sodium and Cephradine

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Abstract
Two rapid and simple spectrophotometric methods as well as a selective and sensitive spectrodensitometric procedure are described for the determination of cephalothin sodium (CT) and cephradine (CD). The spectrophotometric methods are based on the charge-transfer complex formation between these derivatives as n-donors and iodine, the o-acceptor or 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ, π-acceptor). The obtained charge-transfer complex with iodine shows two maxima at 295 and 365 nm in 1.2-dichloroethane while it shows a single maximum at 460 nm wih DDQ in methanol. Beer's law is obeyed in a concentration range of 2–30 and 2–16 μg/ml with iodine; 10–120 and 30–270 μg/ml with DDQ for CT and CD respectively. In the spectrodensitometric method, cephalosporin derivatives are separated from their degradation or additive products on high performance thin-layer silica gel G plates. The plates were then developed, air dried, exposed to iodine vapour and measured on a spectrodensitometer at 290 and 360 nm for CD and CT respectively. The proposed methods are successfully applied to the analysis of CT and CD dosage forms.