Colorimetric determination of a polymeric quaternary ammonium antimicrobial preservative in an ophthalmic solution.
A simple colorimetric method is presented for the determination of Polyquad, a polymeric quaternary ammonium antimicrobial preservative, in an ophthalmic solution. Polyquad and magnesium are coprecipitated by ion pairing with Ponceau S, a highly colored sulfonate dye, at an acidic pH. The sample is centrifuged and the supernate analyzed spectrophotometrically. The concentration of Polyquad is determined by the decrease in dye concentration. Formulation excipients such as disodium edetate, dextran, and hydroxypropylmethylcellulose did not interfere with the quantitation. The method is specific, accurate, precise, and stability-indicating for the quantitation of 10 ppm Polyquad.
Alcon Laboratories, Inc., Fort Worth, TX 76115.
R M
RM
Good
J C
JC
Liao
M J
MJ
Hook
C L
CL
Punko
D003124:Colorimetry; D007202:Indicators and Reagents; D009883:Ophthalmic Solutions / Q000032:analysis*; D010592:Pharmaceutic Aids / Q000032:analysis*; D011108:Polymers; D011310:Preservatives, Pharmaceutical / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis*
D007202:Indicators and Reagents; D009883:Ophthalmic Solutions; D010592:Pharmaceutic Aids; D011108:Polymers; D011310:Preservatives, Pharmaceutical; D000644:Quaternary Ammonium Compounds