Determination of Clozapine by Air Assisted Dispersive Liquid-Liquid Microextraction Based on Solidification of Organic Droplet Followed by HPLC in Human Serum

Due to the challenges of maintaining serum levels in a safe therapeutic range (1–3 μM), Clozapine is one of the most promising medications for managing schizophrenia. Recently the barrier to the broader use of clozapine has been recognized to be the measurement of clozapine levels, which is however challenging due to the complexity of serum samples. The determination of clozapine is mainly conducted through a novel, simple, rapid and sensitive air assisted dispersive liquid-liquid microextraction based on solidification of organic droplet method that has been developed and validated by high-performance liquid chromatography with UV detection in human serum. In this method, due to the usage of an organic solvent with a low density and appropriate melting point, no microsyringe or fiber is required to support the organic microdrop. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1-Undecanol was selected as extraction. The optimization of Parameters that influence extraction efficiency, i.e., volumes of extracting solvent, pH, and salt effect, were performed using a factor by factor approach. Enrichment factor for clozapine under optimal conditions was 128. The limit of detection was 1.34 ng/mL in serum sample. The proposed method was successfully applied to the determination of clozapine in serum samples of a person under clozapine therapy.