MEASUREMENT OF SALICYLSALICYLIC ACID AND SALICYLIC-ACID IN PLASMA BY HIGH-PRESSURE LIQUID-CHROMATOGRAPHY

  • 1 January 1979
    • journal article
    • research article
    • Vol. 9  (6) , 501-510
Abstract
The analgesics salicylsalicylic acid (SS) and salicylic acid (SA) appear in plasma after the oral ingestion of SS. They can be estimated in the presence of each other after extraction into dichloromethane using high pressure liquid chromatography. SS is unstable in human plasma, being converted to SA in vitro. Conversion can be prevented by using EDTA as an anticoagulant and carrying out the extraction in the cold. An aliquot of the extract is dried and dissolved in methanol. Weak solutions of SS in methanol are unstable at room temperature. Methanolysis can be prevented by the addition of dilute HCl. By adding phenylbutazone to the plasma as an internal standard, variations in extraction and sample application are nullified. Quality control is achieved by concurrent extraction of 2 different plasma standards containing SS and SA in known amounts. About 40 ng of SS and SA can be detected; reproducibility at 200 ng and above is better than 6.5%.