o-Phthalaldehyde based spectrophotometric determination of sulfonamides.
o-Phthalaldehyde (OPA) reacts with primary amino group in a compound in presence of a thiol (RSH) and in an alkaline medium to give a soluble product called isoindole. This is a fluorescent compound, yet it has been exploited for spectrophotometric study by measuring the absorbance at 340 nm which is the wavelength for excitation of the molecule. The spectrophotometric method has successfully been employed in the quantitative estimation of sulfonamides such as sulfadiazine, sulfanilamide and sulfamethoxazole, all containing a primary amino group. The detection ranges from 0.01 to 0.24 mg/ml of the active ingredient in different samples containing sulfonamides. The respective standard curves were linear in the given range and the relative standard deviation of the mean response factor ranged from 1.95-2.08%. 2-methyl-2-propane thiol (2MPT) has been used in the derivatization reaction for the formation of OPA-adduct and borate buffer of pH 10.0 has been used to maintain the medium alkaline.
Vaid
Faiyaz H M
FH
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Karachi, Karachi.
Aminuddin
M
M
Mehmood
Karamat
K