A Sensitive Method for the Determination of Methadone in Biological Samples Using Nano-Structured α-Carboxy Polypyrrol as a Sorbent of SPME

Nano-structured alpha-carboxy polypyrrol (PPy- alpha-COOH) was used as a coating of solid-phase microextraction (SPME) fiber to increase the extraction efficiency of headspace solid phase microextraction (HS-SPME) of methadone (MDN) in biological samples. The carboxy-endcapped polypyrrole film was prepared via electrochemical deposition on a platinum wire. A nano-fibrous structure of PPy-alpha-COOH with a diameter of 120 nm was obtained. The porous surface structure of the film, revealed by scanning electron microscopy, provided high surface areas and allowed for high extraction efficiency of methadone. Then the analysis of the extracts was carried out by a gas chromatography-flame ionization detector. In order to achieve maximum extraction efficiency, different parameters affecting the extraction conditions were optimized. Under the optimized conditions, the limit of detections and the limit of quantifications of the method in the range of 0.02-0.035 and 0.06-0.10 mu g L-1 were obtained for different matrices. The relative recoveries in different samples were in the range of 95-97%. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of MDN in human urine and plasma samples in the range of microgram per liter, and suitable results were obtained (RSDs < 5.3%).