Determination of antibiotic drug concentrations in circulating human blood by means of solid phase micro-extraction

BackgroundPromising results in animals have shown the diagnostic potential of polypyrrole coated SPME fibres introduced directly into the blood stream. This study was intended to extend this technique to a clinically relevant antibiotic drug under close to physiological conditions in human blood.MethodsAn artificial vein system was built up from heart and lung machine components. Determination of Linezolid (0–15 μg/mL) was performed by SPME from the flowing system (“online”, flow velocities 2–50 cm/s), from blood withdrawn from the system (“offline”) and by means of a SPE/HPLC method. SPME was done using new fibres (“new”) for each analysis, and in the way that one fibre was reused (“re”) for one series of measurements.ResultsDrug SPME did not depend on blood flow velocities. Linear regression of data (concentration vs. amount extracted) yielded R2 = 0.998 for SPE/HPLC, R2 = 0.955 for SPMEonline_new, 0.929 for SPMEonline_re, 0.929 SPMEoffline_new, 0.973 for SPMEoffline_re, RSD were 52% (SPMEonline_new), 10% (SPMEonline_re), 47% (SPMEoffline_new), 18% (SPMEoffline_re), 8% (SPE/HPLC).ConclusionsIn-vein SPME has the potential to minimize blood requirement for diagnostic purposes and to speed up analysis of clinically relevant drugs, if inter-fibre variation can be reduced through standardized manufacturing.