Highly Selective Coated–wire Potentiometric Sensor for Determination of Oxycodone in Plasma and Urine

The construction and electrochemical response characteristics of polyvinyl chloride (PVC) membrane sensor for the determination of oxycodone are described. An ion–pair of oxycodone–sodium tetraphenyl borate was used as an electroactive material and dibutyl phthalate (DBP) as an anion excluder in a PVC matrix in the percentage ratio of 2.70:61.30:36.00 (w/w). This potentiometric sensor exhibits a linear response to oxycodone in a concentration range of 1.0×10–6 to 1.0×10−2 M with a limit of detection of 9.4×10−7 M and with a slope of -56.10 mV/decade over the pH range 4.0–9.0. The selectivity coefficients of the sensor for oxycodone relative to a numbers of potential interfering compounds were investigated. The sensor is highly selective for oxycodone over a large number of similar compounds. The new sensor showing a fast response time of 15 s and was used over a period of 2 month with a good reproducibility. The sensor was successfully applied to determine oxycodone in urine and blood serum samples with satisfactory results.