Titrimetric micro-determination of therapeutically active phenothiazines using periodate

Two new simple, accurate and precise titrimetric micro-procedures are described for the analysis of phenothiazines in pure sample, tablets, injections and syrup using periodate as the oxidant. The first method is based on the oxidation of phenothiazines with periodate in acid medium and the iodate formed in the reaction is determined by reacting it with iodide and titrating the liberated iodine with thiosulfate after masking the excess of periodate with molybdate. In the second procedure, the unreacted (excess) periodate is determined iodometrically under basic conditions. The reaction conditions have been optimised and the stoichiometry of the reaction has been evaluated. A linear relationship exists between the amount of the drug and the titration end-point as shown by the values of correlation coefficient, r (0.9991-0.9999). The slope of the linear relationship has been calculated and found to be in the range, 0.1457-0.3120. The methods were applied to the analysis of dosage forms with results comparable to those given by the official methods. Both the methods are indirect visual titration methods, and are simpler than, and superior to, many existing methods for the assay of phenothiazines.

Application of potassium dichromate and iron-thiocyanate in the spectrophotometric investigations of phenothiazines

A spectrophotometric procedure for the determination of phenothiazines in pure form and in a number of their pharmaceutical preparations has been developed that offers the advantages of simplicity, accuracy, precision and sensitivity over many other methods. The method is based on the oxidation of phenothiazines by a known excess amount of potassium dichromate followed by the estimation of unreacted amount of dichromate by reacting with excess of iron(II) and measuring the iron(III) formed by complexing with thiocyanate. The reacted oxidant corresponds to the drug content. Different variables affecting the reaction between drugs and dichromate were studied and optimized. At the maximum absorption of 480 nm, Beer's law is obeyed in the range 2.5-29.75 microg/ml. The molar absorptivity and Sandell sensitivity of the procedure were calculated in addition to detection limit. Statistical treatment of the experimental results indicates that the procedure is precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedure. The reliability of the method was established by parallel determination against the official BP methods. The procedure described was successfully applied to the determination of the bulk drugs and in pharmaceutical formulations.

A highly sensitive spectrophotometric method for the determination of some phenothiazine antipsychotics using chloramine-T and indigocarmine

A new simple, accurate and precise spectrophotometric method for the determination of six phenothiazine drugs in pure form and in dosage forms is described. The method is based on the oxidation of the studied drugs by a known excess of Chloramine-T in hydrochloric acid medium and subsequent determination of the unreacted oxidant by reacting it with indigocarmine in the same acid medium. The reacted oxidant corresponds to the drug content. The colored species exhibits maximum absorption at 610 nm. The apparent molar absorptivity values and Sandell sensitivity values are in the range 1.53 x 10(4)-2.96 x 10(4) l mol-1 cm-1 and 13.75-37.15 ng cm-2, respectively. The method is highly sensitive and suitable for 1-15 micrograms ml-1 concentrations with the detection limits being in the range, 0.0651-0.1724 microgram ml-1. The method was successfully applied to the studied drugs in their dosage forms. The results are reproducible within +/- 1% and compare favorably with those obtained by the procedures of the British Pharmacopeia.

Quantitation of pharmaceutically important phenothiazines by oxidimetry

A new spectrophotometric method for the assay of phenothiazines in pure form as well as in pharmaceutical formulations with the chromium(VI)-metol-sulfanilic acid system has been developed. The method is based on the oxidation of the drugs by a known excess of chromium(VI) and subsequent determination of the unreacted oxidant by interacting with metol and sulfanilic acid. The reacted oxidant corresponds to the drug content. The coloured species exhibits maximum absorbance at 530 nm. Beer's law is obeyed over the concentration range 5-60 micrograms ml-1 and the relative standard deviation is found to be less than 2%. The apparent molar absorptivities are in the range 3.77 x 10(3)-3.98 x 10(3) l mol-1 cm-1, the detection limits being in the range 0.6133-1.1349 micrograms ml-1. The method was successfully applied to the determination of the studied drugs in their formulations and the mean percentage recoveries were found to be 97.32-102.80%.