Paper electrophoresis in the study of mixed ligand complexes in solution. The system Fe(III)- and Cr(III)-methyl cysteine-penicillamine

Paper electrophoretic determination of the stability constants of binary and ternary complexes of copper(II) and cobalt(II) with nitrilotriacetate and cysteine

A paper ionophoretic method is described for the study of equilibria in mixed ligand (nitrilotriacetate-cysteine) complex system in solution. The proportion of ionic species of nitrilotriacetate (NTA) and cysteine were varied by changing the pH of background electrolyte. The stability constants of Cu(II)-NTA-cysteine and Co(II)-NTA-cysteine complexes were found to be 6.35+/-0.05 and 5.45+/-0.02 (logarithm stability constant values), respectively, at ionic strength 0.1 M and a temperature of 35 degrees C.

Spectrophotometric estimation of D-penicillamine in bulk and dosage forms using 2,6-dichloroquinone-4-chlorimide (DCQ)

A simple colorimetric method for the determination of D-penicillamine in pure form and pharmaceutical formulations is described. The method is based on coupling between D-penicillamine and 2,6-dichloroquinone-4-chlorimide (DCQ) in dimethylsulphoxide. The optimum conditions for the reaction were investigated and incorporated into the procedure. The reaction forms a yellow 1:1 complex with maximum absorbance at 431 nm (epsilon = 3,700). Regression analysis of Beer's plot showed good correlation (r = 0.9998) and the calibration graph was rectilinear over the range 4-20 microg/ml(-1) with a detection limit of 0.15 microg/ml(-1) . The average recovery for the commercial capsules was 101.66% with an RSD of 1.57%. The results obtained were sufficiently accurate, reproducible and in accordance with those given by the official method. The method is specific for the intact drug, and can be adopted in the presence of some interfering substances.