Colorimetric determination of disulfiram in tablets: collaborative study

The colorimetric reaction of cuprous iodide and disulfiram has been collaboratively studied in 8 laboratories to determine the drug in tablet form at 2 dosage levels. The disulfiram was extracted from the tablet matrix with methylene chloride. After a basic wash with 1 M NaOH, an aliquot of the methylene chloride solution was reacted with solid cuprous iodide, and the absorbance of the resulting color was measured. Single assays on 2 synthetic preparations of known disulfiram content were performed with average recoveries of 98.4 and 99.2% for 93.3 and 105.3 mg, respectively. Duplicate determinations on 2 commercial tablet preparations declared at 250 and 500 mg gave mean and standard deviation values of 246.6 +/- 6.40 and 493.6 +/- 12.0 mg, respectively. The results agreed closely with those obtained by the author using the NF iodometric titration procedure. The method has been adopted official first action.