Sorbent-less dried blood spot microsampling

Abstract

Dried blood spots (DBSs) are typically sampled on porous sorbents, which may retain analytes in their structure during DBS rehydration but also release various species into the eluates and contaminate them. To eliminate the eluate contamination, a novel concept for sorbent-less DBS microsampling was suggested, and a comprehensive study was carried out investigating the effect of the novel and the standard DBS sampling procedures on the contamination. In the novel concept, a small drop of capillary blood with a known volume was quantitatively pipetted into a non-porous polypropylene vial (compatible with capillary electrophoresis (CE) instruments for subsequent analysis) without being absorbed by any sorbent. All procedures, including DBS sampling, drying, rehydration, and homogenization, were done directly in-vial, and the blood drying time was < 3 h. By neglecting the porous sorbent, contamination of the resulting DBS eluates by sorbent-borne species was eliminated, which was demonstrated by the CE determination of inorganic cations/anions and organic anions. The ionic composition of the rehydrated sorbent-less DBSs showed no statistical difference from the original liquid capillary blood. On the contrary, all commercial sorbents released considerable levels of ions into the eluates (Ca2+, Mg2+, Na+ and Cl-, NO3-, SO42-, HCOO- being the major cationic and anionic contaminants, respectively), resulting in up to 3.5-fold higher concentrations in standard vs. sorbent-less DBS samples and having a detrimental effect on quantitative DBS analyses. Moreover, additional ionic contamination was observed for DBSs sampled on pre-impregnated sorbents and/or by volumetric devices treated with anticoagulants. Consequently, a simple, precise, and accurate procedure was presented for sorbent-less DBS microsampling in medical as well as patient-centric conditions. The most convenient and economical DBS sampling was achieved by a low-cost micropipette with adjustable volume, resulting in precision and accuracy of 1.7 and 1.4%, respectively, for quantitative blood transfers, and CE analyses repeatability of 7.2%, after the whole DBS processing.