Application of surfactant assisted dispersive liquid–liquid microextraction as an efficient sample treatment technique for preconcentration and trace detection of zonisamide and carbamazepine in urine and plasma samples

• The preconcentration of CBZ and ZNS with surfactant assisted dispersive liquid–liquid microextraction is optimized.
• Water with low concentration of surfactant is used as dispersed solvent.
• Simultaneous trace determination of carbamazepine and zonisamide in biological samples.
• The proposed method is simple, rapid, cheap and environmentally friendly.

A simple, rapid, and efficient method, based on surfactant assisted dispersive liquid–liquid microextraction (SA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for simultaneous preconcentration and trace detection of zonisamide and carbamazepine in biological samples. A conventional cationic surfactant called cethyltrimethyl ammonium bromide (CTAB) was used as a disperser agent in the proposed approach. 1.5 mL of CTAB (0.45 mmol L−1) (disperser solvent) containing 50.0 μL of 1-octanol (extraction solvent) was injected rapidly into the 7.0 mL of water or diluted plasma or urine. A cloudy solution (water, 1-octanol, and CTAB) was formed in the test tube. After formation of cloudy solution, the mixture was centrifuged and 20 μL of collected phase was injected into HPLC for subsequent analysis. Some parameters such as the type and volume of the extraction solvent, the type and concentration of surfactant, pH, ionic strength and centrifugation time were evaluated and optimized. Under optimum extraction conditions, the limits of detections (LODs) were 2.1 and 1.5 μg L−1 (based on 3Sb/m) for urine samples, and 2.3 and 1.6 μg L−1 for plasma samples. Linear dynamic range of 5–300 and 5–200 μg L−1 were obtained for zonisamide and carbamazepine in all samples. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine and plasma samples.