USE OF AN IMPROVED VERSION OF C8+SCX MIXED-MODE SOLID PHASEEXTRACTION MATERIAL FOR CLEAN EXTRACTION AND RECOVERY OFBASIC, ZWITTERIONS, NEUTRAL AND ACIDIC COMPOUNDS FROMBIOLOGICAL FLUIDS

摘要

Reliable and reproducible screening and isolation of drugs, their metabolites as well as poisons fromrnbiological matrices is the first, the most important and the most critical step in pre-clinical, clinical andrnforensic analyses (1,2). Among various extraction methods, silica-based mixed-mode SPE cartridges andrn96-wells, containing reversed-phase and cation-exchange compositions, is one of the most versatile SPErnproducts in the market because of owning generic extraction methods, and a number of successfulrnapplications for cleaner extraction of basic compounds from biological fluids as well as acidiceutral/basicrndrug screens (1-3). However, in spite of these obvious advantages, the products from the currentrnmanufacturers may have some serious problems. Several authors have claimed that very differentrnrecoveries, up to complete failure of the extraction, are observed for the same or different lots and vendors.rnThe present study offers evidence that the products from current vendors have the risk for losing weaklyrnand polar basic compounds, and polar zwitterions compounds during the extraction. In addition, somernzwitterions compounds co-exist in both the neutral/acid fraction and the basic fraction, making the furtherrnanalysis complicated. This is primarily due to the low ion-exchange capacity inherent with current phasesrncommercially available. When the cation-exchange capacity is lower than a critical value, any changesrnregarding the types and the amount of the elution solvents, the total amount of SPE material used, thernvariation of ion-exchange capacity from lot-to-lot, and other experimental factors will affect thernreproducibility. Since the same columns and the same elution protocols are used, the reproducibility is stillrnpoor sometimes, evidenced by 2-aminopyridine, cytosine and other examples described in the presentation.rnIn this presentation, we describe the use of the next generation of C8+SCX mixed-mode SPE product inrnwhich SCX coverage has been optimized. As a major characterization data, the cation-exchange capacityrnof the novel product is 1.5-4 times higher than those from the current vendors. Three generic extractionrnprotocols have been determined. The first protocol offers superior selectivity when recovering non-polar to