Determination of quaternary ammonium surfactants in pharmaceutical formulations by the hypochromic effect.
A spectrophotometric procedure for determination of the quaternary ammonium salts cetrimide (N,N,N-trimethyl-l-hexadecylammonium bromide), cetylpyridinium chloride (l-hexadecyl-pyridinium chloride) and sapamine [N-(2-dimethylaminoethyl)oleamide acetate] in bulk form and some pharmaceutical formulations, such as eye-drops, disinfectant solutions, creams and tablets, is described. Following TLC separation when necessary, addition of an aqueous solution of the active surfactant to a standard amount of Bromothymol Blue, buffered at pH 7.5, leads to an equivalent decrease of the absorbance at 610 nm, which can be taken as an analytical measure of the drug concentration. Good mean recoveries have been obtained for standard additions of these analytes to pharmaceutical formulations containing them.
El-Khateeb
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SZ
King Saud University, College of Pharmacy, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
Abdel-Moety
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EM