Automated Sequential Injection-Capillary Electrophoresis for DriedBlood Spot Analysis: A Proof-of-Concept Study

A hyphenated analytical platform that enables fully automated analyses of dried blood spots (DBSs) is proposed bythe at-line coupling of sequential injection (SI) to capillary electrophoresis (CE). The SI system, exploited herein for thefirst timefor unattended DBS handling, serves as the"front end"mesofluidic platform for facilitating exhaustive elution of the entire DBS byflow programming. The DBS eluates are thus free from hematocrit and nonhomogeneity biases. The SI pump transfers the resultingDBS eluates into CE sample vials through an internal port of the CE instrument and homogenizes the eluates, whereupon the elutedblood compounds are automatically injected, separated, and quantified by the CE instrument. The SI and CE are commerciallyavailable off-the-shelf instruments and are interconnected through standard nuts, ferrules, and tubing without additional instrumentaladjustments. They are controlled by dedicated software and are synchronized for a fully autonomous operation. The directdetermination of endogenous (potassium and sodium) and exogenous (lithium as a model drug) inorganic cations in DBS sampleshas been used for the proof-of-concept demonstration. The hyphenated SI-CE platform provides excellent precision of the analyticalmethod with relative standard deviation (RSD) values of peak areas below 1.5 and 3.5% for intraday and interday analyses,respectively, of the endogenous concentrations of the two inorganic cations. For the determination of lithium, calibration is linear ina typical clinical range of the drug (R2better than 0.9993 for 2-20 mg/L), RSD values of peak areas are below 4.5% (in the entirecalibration range), the limit of detection (0.4 mg/L) and the limit of quantification (1.3 mg/L) are well below the drug's minimumtherapeutic concentration (4 mg/L), and total analysis time is shorter than 5 min. The SI-CE platform reflects the actual trends inthe automation of analytical methods, offers rapid and highlyflexible DBS elution/analysis processes, and might thus provide ageneral solution to modern clinical analysis as it can be applied to a broad range of analytes and dried biological materials.