Development of an efficient capillary electrophoresis method for the analysis of salting-out assisted liquid-liquid...

A novel method based on salting-out assisted liquid-liquid extraction (SALLE) combined with capillary electrophoresis coupled to UV detection (CE-UV) was developed for the analysis of anticancer drugs in plasma samples. The SALLE technique allowed efficiently extraction of anticancer drugs from plasma into the organic phase, which was further analyzed by CE-UV. However, first experiments revealed instability in current profiles and UV electropherograms affected the performances of the SALLE-CE-UV method. To address these issues, different background electrolytes (BGEs) were tested to improve the stability and performance of the method. In parallel, microfluidic devices were also used to study the mixing between SALLE-extracted plasma samples and BGEs within the silica capillary. This approach provided key insights into SALLE-CE-UV optimization, highlighting issues such as phase separation, precipitation, and air bubble formation. These were mitigated by introducing an intermediate plug (2-fold diluted BGE) between the SALLE sample and the 100 mM pH 2.0 citric acid/ε-aminocaproic acid BGE, which significantly improved current stability. Further optimization of voltage ramp times (4 min from 0 to +15 kV) and temperature conditions (40 °C) improved method performances. The optimized procedure, applied to three tyrosine kinase inhibitors (TKIs), imatinib mesylate (IMA), axitinib (AXI), and erlotinib hydrochloride (ERL), used for the treatment of malignant tumors, demonstrated excellent linearity (coefficient of determination (R²) ≥ 0.995 from 0.15 to 0.75 mg/L), (R² ≥ 0.994 from 30 to 80 % of the injected volume to the detection window) repeatability (Relative standard deviation (RSD) ≤ 3.2 and 4.3 % on migration times and corrected peak areas), and sensitivity (Limit of detection (LOD) of IMA, ERL and AXI: 40.3, 79.3 and 40.6 ng/mL respectively) with UV detection at 254 nm.