Electrochemically controlled in-tube solid phase microextraction of naproxen from urine samples using an experimental design

A new in-tube solid phase microextraction approach named electrochemically controlled in-tube solid phase microextraction (EC in-tube SPME) has been reported. In this approach, in which electrochemistry and in-tube SPME were combined, the total analysis time was decreased and the sensitivity was increased. After electropolymerization of pyrrole on the inner surface of a stainless steel tube, the polypyrrole (PPy)-coated in-tube SPME was coupled on-line to high performance liquid chromatography (HPLC) to achieve automated in-tube SPME-HPLC analysis. After the completion of the EC-in-tube SPME-HPLC system, the PPy-coated tube was used as a working electrode for the uptake of naproxen. It was found that the extraction efficiency could be significantly enhanced using the constant potential. Plackett-Burman design was employed for screening, to determine the variables significantly affecting the extraction efficiency. The significant factors were then optimized using a Box-Behnken design. The linear range and detection limit (S/N = 3) were 0.5-1000 and 0.07 mu g L-1, respectively. Urine samples were successfully analyzed by the proposed method.