[59] Extraction and thin-layer chromatography of arachidonic acid metabolites

This chapter discusses the extraction and thin-layer chromatography of arachidonic acid metabolites. In some cases prostaglandins may be determined directly in aqueous samples (e.g., radioimmunoassay or bioassay of tissue perfusates and cell culture fluids) without recourse to extraction, but more usually, extraction into an organic solvent is a prerequisite to separation and/or quantitation. The advantages of extraction are that it eliminates protein, imparts some specificity to the assay and, by concentrating material, improves the sensitivity of the analysis. The choice of any particular extraction technique is governed by its efficiency, specificity, reproducibility, and practicability. The extraction procedures efficiently remove all fatty acids, prostaglandins, and other hydroxy acids, but obviously if specific analysis of a particular compound is required some further purification is necessary. Many chromatographic procedures can be employed for analysis of prostaglandins, but thin layer chromatography has much to commend it in terms of efficiency, simplicity, and economy of money and effort.