Application of molecular imprinted polymers based stir bar for selective extraction and pre-concentration of carbamazepine in biological samples

Carbamazepine(CBZ), 5-H-dibenze[b,f]azepine-5-carboxamide, is the most frequently prescribed first-line drug for the treatment of simple and complex partial seizures and psychiatric diseases [1]. It is almost completely metabolized in the body and only small traces are excreted unchanged in urine. The pharmacokinetic characteristics of CBZ are complex; there is no simple relationship between the dose of CBZ and concentration of the drug in body fluids. Therapeutic concentrations have been reported to be 2–12 μg/ml, although considerable variations may arise [2]. As we know, analysis of most of drugs in the biological samples are challenging due to the complexity of these matrices. The presence of endogenous interferences, such as proteins in plasma, serum and inorganic salts in urine demands sample pretreatment prior to the analytical determination. So, the sample preparation procedures are an undeniable step in drug analysis [3, 4]. In this work, we synthesized and developed a selective molecular imprinted polymer (MIP) based stir bar for pre-concentration of low level of CBZ in biological samples especially urine and serum. The capability of the developed selective stir bar for pre-concentration of CBZ as an analyte, were investigated with a magnetic solid-phase extraction method. In this method, a stir bar coated with polyamide was placed in the 2 mL sample solution containing CBZ in desired concentration and the sorption was carried out for 20 min while stirring at 900 rpm. After extraction, the stir bar was removed from the sample solution with tweezers and the analyte desorbed into 500 μl vial containing 10% (v/v) acetic acid/methanol. Desorption of the CBZ was performed stirring for 15 min. 50 µL of the extract solution were injected into the HPLC-UV system. Chromatographic separation was achieved in approximately 10 min on a reversed-phase C18 column using a ternary mixture of potassium dihydrogen phosphate buffer (pH 6.0)/acetonitrile/2-propanol (63:22:15, v/v) as the mobile phase, at a flow rate of 1.0 mL/min. The UV detector was set at 220 nm. Calibration curves were linear with regression coefficients greater than 0.992 over the concentration ranges 0.1–12 μg/mL for CBZ. Applying this adsorbent enables access to accurate and precious information about CBZ levels in the body fluids and it seems to be a simple and suitable tool for routine therapeutic drug monitoring.