Microdialysis sampling and high-performance liquid chromatography with chemiluminescence detection for in-vivo on-line determination and study of the pharmacokinetics of levodopa in blood

A simple, reliable, and reproducible method for in-vivo on-line separation and determination of levodopa has been based on microdialysis then high-performance liquid chromatography with chemiluminescence detection. The perfusate is perfused at a flow rate of 5 μL min−1. The concentration of levodopa in the dialysate is determined on line with a chemiluminescence system. The dialysate sample volume is approximately 20 μL. The response of the system is linearly related to the concentration of levodopa in the range 1×10−8 to 1×10−6 g mL−1 (r2=0.9995) with a detection limit (3σ) of 3×10−9 g mL−1 and sample throughput of 12 h−1; RSD is 2.8% (n=11). The method has been successfully used to study the pharmacokinetics of levodopa in vivo; the values of the pharmacokinetics parameters Cmax, AUC0–t and Tmax were 16.60, 20.92 ng mL−1, and 90 min, respectively.