Hematocrit-independent recovery of immunosuppressants from DBS using heated flow-through desorption.

BACKGROUND: We applied our concept for automated flow-through desorption of DBS to investigate the effect of desorption temperature on recovery. For this purpose, a method has been developed for the determination of four immunosuppressants in DBS. RESULTS: We compared recoveries of four immunosuppressants for measurements with and without temperature-enhanced desorption at different hematocrit (Ht) levels. Temperature-enhanced desorption increased recovery substantially for tacrolimus, sirolimus and everolimus at all Ht values and for cyclosporine At high Ht. In addition, recovery became largely independent from Ht variations. Under the optimized conditions, a brief validation using spiked blood samples showed that the method complies with acceptance criteria for quantitative bioanalysis. CONCLUSION: This method enables a quantitative analysis of immunosuppressants in DBS independent from the Ht.

Exploration of a new concept for automated dried blood spot analysis using flow-through desorption and online SPE-MS/MS.

BACKGROUND: A new concept for simple and generic automation of dried blood spot (DBS) analysis is evaluated. Flow-through desorption of the blood spot is coupled online to SPE and MS/MS without using a LC column. Blood, spiked with a mixture of test compounds is spotted on paper, dried and then desorbed by means of a prototype clamping device. RESULTS: Conditions for extraction and chromatography on a single SPE cartridge were optimized with respect to clean-up, separation and ionization suppression. Addition of internal standard using loop-injection upstream of the clamped blood spot was examined and proved to be simple and reliable. Validation results for the 1-1000 ng/ml range are well within acceptance criteria for bioanalysis. CONCLUSION: Results demonstrate feasibility of the DBS SPE-MS/MS concept for efficient automation of the entire DBS analysis workflow.