Phenobarbital in pharmaceutical tablets by modified conductimetrical analysis

A simple and reliable assay for Phenobarbital in tablets, by modified conductimetric titration was developed. The use of ammonium hydroxide addition enhanced the acidity of Phenobarbital and allowed its indirect determination, with NaOH as titrant. Optimal Work conditions were established to perform assays with tablets containing 100 mg of phenobarbital provided by the Medical Plant of Corrientes (PLAMECOR) Argentina. The proposed method was found to be highly precise, having a relative standard deviation (CV) below 2.0% in repeatability and intermediate precision studies. Using this approach the calibration curve showed r 2 = 0.9996 with a linearity range from 50 to 150 mg. Accuracy based on the average recovery of known amounts of drug in placebo was 100.15% ± 1.31, value included inside the limits established by USP. Trivial signal in titration of placebo demonstrated the high specificity of this method. Measurements were compared with determinations by the reference method (HPLC), using two tails Student`s statistical t-test. It C. M. Monzon et al. 102 was established with a 95% confidence level, that there are no significant differences among results obtained with both methods. The modified conductimetric titration method is preferred due to its simplicity, ease, low cost and absence of pre-treatment procedures of the samples