A new approach for decreasing the detection limit for a ketamine(I) ion-selective electrode

Our endeavors of lowering the detection limit for a ketamine(I) ion-selective electrode were described. The paper stresses the electrode which showed best results for determination of ketamine ion. The present electrode incorporates ketamine-phosphomolybdate (KT-PM) as ion-exchanger combined with the lipophilic anionic additive (Na-TPB) dissolved in dibutyl phthalate (DBP) as a plasticizer. The characteristics of the electrode were elaborately measured and its performance was tested in various samples and urine. It has favorable features as it provides measurements of the potential with a near-Nernstian slope of 56.6 +/- 0.3 mV/decade over the concentration range of 1.5 x 10(-6)-1.0 x 10(-2) M over the pH range 3.0-6.8 in a short response time (7 s). Importantly, it has a low detection limit of 1.2 x 10(-7) M and its life-span is 22 days. Moreover, it displayed notable selectivity for ketamine ion over other species such as inorganic and organic cations and different excipients which may be present in pharmaceutical preparations. The sensor was applied for determination of KT ions in urine and pharmaceutical preparations using potentiometric determination, standard addition and the calibration curve methods. The standard deviation computed on the results indicated excellent repeatability of the measurements. Overall, it showed satisfactory results with excellent percentage recovery comparable to and sometimes better than those obtained by other routine methods for the assay. (C) 2015 Elsevier B.V. All rights reserved.