Automated Liquid Extraction Surface Analysis (LESA) from a Dried Blood Spot Card Holder via Chip-Based Nanoelectrospray

This report describes a novel dried blood spot (DBS) card holder equipped with four defined surface extraction areas suitable for automated liquid extraction surface analysis (LESA) of dried biological sample spots. In brief, a commercially available DBS card containing four spotted whole blood samples is manually inserted into the card holder while a hinged cover containing a sequence of four circular ridges is clamped directly onto the sample substrate surface to define four constrained surface extraction regions for each sample. The LESA technique is then implemented by sequentially delivering a pipette tip containing a sample extraction/electrospray solvent to the sample surface. Analytes extracted from the DBS sample are then analysed directly by infusion nanoelectrospray mass spectrometry. Amlodipine and its tetradeuterated internal standard produced a linear calibration curve from 10 ng/mL to 10,000 ng/mL from fortified human whole blood with acceptable accuracy and precision using this approach.