SPECTROPHOTOMETRIC DETERMINATION OF BENZALKONIUM CHLORIDE IN DOSAGE FORMS THROUGH CHARGE-TRANSFER COMPLEXATION

Two simple and sensitive spectrophotometric methods are described for the determination of benzalkonium chloride which is added as a preserv ative in certain dosage forms. The methods are based on the formation of highly coloured stable radical anions between benzalkonium chloride as n-electron donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ) or 2, 3-dichloro-5,6dicyano-p-benzoquinone (DDQ) as n-electron accepters. Be er's Law is obeyed over the concentration range 0.5 - 8 and 1 - 8 mu g ml(-l) for TCNQ and DDQ respectively. The optimum experimental parame ters for colour production with both reagents were studied and incorpo rated into procedures. The percentage recoveries obtained were in acco rdance with those given by the official method. The proposed methods a re characterized by high sensitivity, satisfactory accuracy and precis ion.