New spectrophotometric method for the determination of some drugs with iodine and wool fast blue BL.

A simple, sensitive and selective method is proposed for the spectrophotometric determination of drugs, viz. ampicillin, penicillin V, amoxycillin, cloxacillin, cefadroxil, ceftezoxime, griseofulvin, streptomycin, nicoumalone and acebutolol HCl, based on their reactivity with iodine. The method involves the addition of excess iodine of known concentration to the drug in the presence of NaOH and the unreacted iodine is determined by the measurement of the decrease in the absorbance of the dye wool fast blue BL (lambda(max)=540 nm) which was found to be the most suitable of several dyes tested. This method was applied for the determination of drug contents in pharmaceutical formulations and enabled the determination of the drugs in microgram quantities (0.8-9.6 mug ml(-1)). No interferences were observed from excipients and the validity of the method was tested against reference methods.

Spectrophotometric determination of bio-active compounds with chloramine-T and gallocyanine.

A simple, sensitive and selective method for the spectrophotometric determination of drugs, viz., sulphamethoxazole, tetracycline HCl, amidopyrine, nifurtimox and isoniazid and biologically important amino acids, cysteine, aspartic acid and arginine based on their reactivity with chloramine-T (CAT) is proposed. The method involves the addition of excess CAT of a known concentration in the presence of 0.25 M HCl and the determination of the unreacted CAT by measurement of the decrease in the absorbance of the dye, gallocyanine (lambda(max): 540 nm), the most suitable of several dyes that were tested. This method was applied to the determination of drug contents in pharmaceutical formulations and to the measurement of the aspartic acid content of some protein hydrolysates. The method is useful for the determination of the target compounds in microgram quantities from 0.4-5.6 microg mL(-1) with the exceptions of arginine (1.0-8.0 microg mL(-1)) and nifurtimox (0.8-5.6 microg mL(-1)). Standard deviations were typically 0.5 mg per dose (RSD 0.5-1.2%). No interferences were observed from common excipients in formulations, and detailed interference studies of other amino acids in the determination of cysteine, aspartic acid and arginine are reported. The validity of the method was tested against spectrophotometric and titrimetric reference methods. Recoveries were 99.8-102.1%.