Semi-automated direct elution of dried blood spots for the quantitative determination of guanfacine in human blood

Background: Direct analysis of dried blood spot (DBS) samples was investigated using a prototype semi-automated robotic device that allows the direct elution of sample spots from a DBS paper card to an online SPE cartridge. The eluted SPE samples were analyzed with high-performance LC–MS/MS. Results: A LLOQ of 0.01 ng/ml was achieved with a linear calibration range from 0.01 to 25 ng/ml. Optimal performance data were obtained from spotting the internal standard solution on the card before blood spotting. Internal standard addition from the system injector loop produced intra-assay inaccuracy of -9.0–7.3% and precision of 1.3–8.2%, and inter-assay inaccuracy of...