Interferences in a high pressure liquid chromatographic assay of theophylline.
Interference by salicylic acid was noted in a high pressure liquid chromatographic assay of theophylline in serum. The acid eluted very close to theophylline in a mobile phase consisting of 0.01 M acetate buffer, pH 4.0, containing 28% methanol on a C-18 reverse-phase column. The two peaks could be resolved by switching to a mobile phase containing 18% methanol, 1.6% acetonitrile, and 1.6% acetic acid in water. However, in this mobile phase traces of the extracting solvent, ethyl acetate, caused a sharpening of the theophylline peak leading to spuriously high results. The problem was overcome by using chloroform to extract the theophylline from serum.
D000085:Acetates / Q000097:blood; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D012459:Salicylates / Q000097:blood; D020156:Salicylic Acid; D013806:Theophylline / Q000097:blood*
D000085:Acetates; D012459:Salicylates; C007650:ethyl acetate; D013806:Theophylline; D020156:Salicylic Acid