Influence of Biological Matrix on Retention Behaviour and Identification Possibilities of Selected Neutral and Acidic Drugs in Thin Layer Chromatography. An Interlaboratory Investigation

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Abstract
Samples of autopsy blood and liver were spiked individually with aminophenazone, p-aminosalicylic acid, clordiazepoxide, clonazepam, cyclobarbital, furosemide, medazepam, phenacetin, phenazone, and phenobarbital and extracted with diethyl ether at pH 5. The extracts, as well as solutions of pure drugs, were developed in three thin layer chromatographic systems: chloroform:acetone (80:20), ethyl acetate:methanol:ammonia (85:10:5) and chloroform:methanol (90:10). The investigations performed in parallel in two laboratories showed that the intra- and inter-laboratory variability of RF values is larger for drugs extracted from liver. The biological matrix affected both precision and accuracy of results. The number of analysts involved in TLC procedures also affected the intra-laboratory precision.