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Three neurotransmitter sensors for dopamine, serotonin, and epinephrine have been developed. Potentiometric sensors for serotonin and epinephrine are novel and first to be introduced. The neurotransmitter potentiometric sensors are based on using dibenzo-30-crown-10 (DB30C10), dibenzo-24-crown-8 (DB24C8), and dibenzo-18-crown-6 (DB18C6) as ionophores and neutral carriers incorporating in poly(vinyl chloride) matrix membrane plasticized with o-nitrophenyl octyl ether. Sensors based on dibenzo-30-crown-10 show good responses for the dopamine, serotonin, and epinephrine (Type I–III, respectively) with a cationic slope of 57.9 mV decade−1 and detection limit of 4.0×10−5 mol L−1 dopamine, cationic slope of 55.9 mV decade−1 and detection limit of 4.0×10−5 mol L−1 serotonin, and cationic slope of 54.4 mV decade−1 and detection limit of 2.0×10−5 mol L−1 epinephrine. The sensors based on DB24C8 and DB18C6 (Types IV–IX) show poor responses in terms of calibration range and slope. The effect of the interferents on the response of the sensors reveals a high selectivity for the neurotransmitters over many inorganic cations, ascorbic and uric acids. The useful pH range for the three sensors is 3–7, the response time is fast (11 s), and the life span is long (2.5 months). Sensors (Types I and III) are successfully used for the quantification of dopamine and adrenaline in pharmaceutical preparations.

The characteristics, performance and application of ion-selective electrodes for bromate ion based on rhodamine B and tetrahexyl ammonium bromide as electrode-active substances are described for the first time. These electrodes respond with sensitivities of (58.0±1.0) and (61.0±2.0) mV decade−1 over the range 1.0×10−8–1.0×10−2 mol l−1 at pH 4–9 and 4–8 and a detection limit of 6.0×10−8 and 4.0×10−8 mol l−1 for rhodamine B and tetrahexyl ammonium bromide sensors, respectively. The electrodes are easily constructed at a relatively low cost, have a fast response time and can be used for a period of 3 months without any considerable divergence in potential. The proposed sensors displayed good selectivity for bromate ion in the presence of several substances and inorganic anions. Sensors were used for the direct assay of bromate ion in drinking water samples.

The present article reports for the first time the use of Aliquat 336S-atorvastatin as an electroactive material in a poly(vinyl chloride) matrix membrane sensor plasticized with ortho-nitrophenyl-octylether (o-NPOE) or dioctylphthalate (DOP) for determination of atorvastatin in biological samples (human plasma) and in pharmaceutical preparations. The sensor shows fast, stable and reproducible response over the concentration range of 1.0×10−7–1.0×10−2 mol L−1 atorvastatin with anionic slopes of 60.94±0.2 and 58.22±0.2 and pH range of 5.0–9.0 for o-NPOE and DOP plasticized based membrane sensors, respectively. The response time of the sensor is stable and fast (10 s). Results were achieved with average recoveries of 99.5 % and 99.3 % and mean standard deviations of ±1.1 % and ±1.4 % for o-NPOE and DOP plasticized based membrane sensors, respectively. The sensor exhibits high selectivity towards atorvastatin in the presence of many anions, drug excipients and diluents. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of the drug.

Simple, selective and accurate sensors were developed for the determination of melatonin and oxomemazine in biological samples (urine) and in pharmaceutical preparations. Potentiometric measurements were based on bismus tetraiodate-drug ion-pair as novel electroactive materials incorporating a plasticized PVC membrane with o-nitrophenyl octyl ether or dioctyl phthalate. Each sensor was conditioned for at least two days in 0.1 M drug solution before use. It exhibited fast and stable Nernstian response for melatonin and oxomemazine over the concentration range of 1.0×10−6–1.0×10−2 M and 1.0×10−5–1.0×10−2 M, pH range of 3.0–6.5 and 3.5–6.0 for melatonin and oxomemazine sensors, respectively. Results with an average recovery not more than 101 % and a mean standard deviation less than 1.0 % of the nominal were obtained for the four sensors. The sensors showed reasonable selectivity towards investigated drugs in presence of many cations.