Extraction of Various Arachidonic Acid Metabolites from Minimal Amounts of Biological Fluid with a New Generation of Miniaturized Solid Phase Extraction Cartridges

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Abstract
Miniaturized solid phase extraction cartridges containing phenyl silyl (PHS), ethyl silyl silica (ESS) and octadodecyl silyl silica (ODS) were compared in their applicability for efficient extraction of 5-lipoxygenase products comprising peptido-leukotrienes (p-LT's), N-acetyl LTE., LTB., the Mono-HETE's (5/12/15), and the cyclooxgenase products TXB2, PGE2, PGI2 and from minimal samples of biological fluid. Recovery rates for radiolabelled eicosanoids were standardized using 100 μ1 human serum or rat bile. Concurrent extraction and chemical integrity of extracted substances were monitored by RP-HPLC and RIA. Whereas ESS allowed 80%86% recovery of prostanoids, LTB4 and 15-HETE ODS yielded 10–20% higher recoveries. Recoveries of 12-HETE and 5-HETE were 93% and 98%, respectively, and comparable results were obtained with ODS as well as in direct recovery of p-LT's, but RP-HPLC revealed loss of radioactivity under the authentic LTC4 peak due to the PHS-protocol. Practical applicability of the cartridges is demonstrated by bedside preparation of suction blister fluid from irritated human skin and processing rat bile continouusly obtained from the cannulated bile duct.