Isolation, separation, and detection of enkephalins: A review of methods for high performance liquid chromatog-raphy and capillary electrophoresis

High Performance Liquid Chromatography(HPLC) and Capillary Electrophoresis (CE) are valuable analytical techniques for the determination of neuropeptides in biological fluids. A crucial aspect of HPLC and CE analyses is the preparation of samples. This review outlines sample preparation protocols for HPLC and CE methods that have been used for this determination, with a focus on enkephalins. Sample preparation protocols have ranged from simple techniques of extraction and centrifugation to solid phase extraction (SPE) and ultrafiltration. Additionally, this review also discusses the final determinant steps of HPLC and CE using various modes of detection. Detection modes for the HPLC methods included ultraviolet (UV), fluorometry, electrochemical and mass spectrometry (MS). Modes of detection when using CE for this determination have been more limited, focusing on UV and MS detection modes.