Diclofenac Sodium Assay – Acidification–Extraction Method
The acidification–extraction assay method for Diclofenac Sodium is a widely used analytical procedure in pharmaceutical quality control laboratories. This method is based on converting Diclofenac Sodium into its free acid form through acidification, followed by extraction into an organic solvent and quantitative determination. It is especially useful for evaluating the purity and potency of raw materials and finished pharmaceutical formulations.
Diclofenac Sodium is the sodium salt of diclofenac, a nonsteroidal anti-inflammatory drug (NSAID) commonly used to relieve pain, inflammation, and swelling. Since the compound is soluble in water in its sodium salt form, acidification with a mineral acid such as hydrochloric acid converts it into diclofenac acid, which is less water-soluble and more soluble in organic solvents like chloroform or ethyl acetate.
In this assay, a measured quantity of Diclofenac Sodium sample is dissolved in distilled water. The solution is then acidified carefully using dilute hydrochloric acid until the pH reaches an acidic range, usually around pH 2. Upon acidification, diclofenac precipitates or becomes extractable into an organic phase. The mixture is transferred into a separating funnel, and extraction is performed multiple times using a suitable organic solvent to ensure complete recovery of the drug.
The combined organic extracts are filtered and evaporated to dryness or analyzed directly depending on the analytical protocol. Quantitative determination may be carried out gravimetrically, spectrophotometrically, or by titration. The assay result is calculated based on the amount of diclofenac recovered compared to the labeled or theoretical amount.
This method provides reliable accuracy and reproducibility when performed under controlled laboratory conditions. Proper pH adjustment, efficient extraction, and complete solvent removal are critical factors influencing the assay outcome. The acidification–extraction technique remains an effective and economical method for routine pharmaceutical analysis of Diclofenac Sodium.