Alginate and chitosan foam combined with electromembrane extraction for dried blood spot analysis

Samples of 10 μL of whole blood containing citalopram, loperamide, methadone, and sertraline as model substances were spotted on alginate and chitosan foams as sampling media. After drying and storage at room temperature, the punched out dried blood spot and the foam was dissolved in 300 μL of 1 mM HCl. With alginate foam as sampling medium, the analytes dissolved completely after 3 min. Enrichment and cleanup was performed with electromembrane extraction for 10 min. The analytes were collected in 21 μL of 10 mM formic acid as the acceptor phase, and the extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS). Sample preparation of blood spots on commercial cards was also performed (Whatman FTA DMPK and Agilent Bond Elut DMS) using elution procedures recommended by the manufacturers. The recoveries obtained with the commercial cards were lower for most of the model analytes compared to the recoveries obtained with alginate and chitosan foams as sampling media. The procedure used for Agilent Bond Elut DMS showed higher recoveries than the procedure used for Whatman FTA DMPK-A, but the time needed for sample preparation was significantly longer (nearly 2 h). The stability of the model substances on the alginate foam was acceptable within 50 days of storage. The limit of quantification (LOQ) defined as S/N = 10, was 1.2, 5.5, 2.0, and 5.3 ng/mL for citalopram, loperamide, methadone, and sertraline, respectively. Linear calibration graphs were obtained in the range 17.5-560 ng/mL with r(2) values 0.983-0.995, and the relative standard deviations were below 20%.