The estimation of acetylsalicylic acid and salicylate in biological fluids by gas-liquid chromatography

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Abstract
A gas‐liquid chromatographic method is described for the simultaneous separation and determination of acetylsalicylic acid (ASA) and salicylic acid (SA) in biological fluids. The salicylates are completely extracted from deproteinized plasma or urine at pH 2 with ether containing p‐toluic acid as the internal standard. The silylated derivatives are formed using bis(trimethylsilyl) trifluoroacetamide and separated at 150° on preconditioned 100–120 mesh Gas‐Chrom Q coated with 5% OV17 packed into a 6 ft, 1/4 inch o.d. glass column in a gas chromatograph with a flame ionization detector and integrator. Detector response is linear over the range from 0–2 mg ml−1 for SA and from 0–100 μg ml−1 for ASA. The time required for the analysis of SA alone or with ASA is about 80 min, the analysis of ASA alone requires about 20 min. The precision of the method is 1 % or better for drug concentrations above 10 μg ml−1. The limits of detectability for SA and ASA are 1 and 2 μg ml, respectively.