LC-MS/MS Quantitation of Isradipine by Supported Liquid Extraction (SLE) and Dried Blood Spot (DBS) Sampling

摘要

An Isradipine 96-well solid supported liquid extraction (SLE) has been validated in human plasma from 50 to 10,000 pg/mL employing Tomtec~(~R) Quadra automation and a Sciex~(~R) API 4000. The assay has been successfully used for the analysis of many thousands of clinical samples. A dried blood spot assay was developed on DMPK-C cards over the same analytical range employing a liquid/liquid extraction technique. Spot to spot reproducibility was found to be very good and comparable to volumetric sampling techniques. The DBS LLOQ signal intensity was adequate, however, lower than the SLE method due to the lower sample volume available; approximately 12 (mu)L/6 mm spot. The extraction of two, 6 mm spots doubled the signal intensity. Spots of isradipine were found to be stable when stored at room temperature in open air for at least 11 days with no observed degradation. This work illustrates the ease by which a plasma assay may be converted to a DBS method. The limits of quantitation were sufficient to support clinical sample analysis and the performance of the assay was comparable to the plasma assay. This then provides an opportunity for clinical costs to be reduced for sample collection and shipping.