Quantitative assay of diclofenac in biological material by gas-liquid chromatography

Diclofenac and an internal standard are isolated from biological samples by acid-specific extraction and converted into the corresponding indolones with 0.5% sulphuric acid in 2,2,2-trifluorethanol. The neutral derivatives are isolated by solvent extraction and subjected to gas-liquid chromatography. The use of an electron capture detector permits the assay of diclofenac at levels down to 2 ng per sample.