ABSTRACT
Bis(2-hydroxyacetophenone)butane-2,3-dihydrazone (BHAB) was used as new N-N Schiffs base which plays the role of an excellent ion carrier in the construction of a Cu(II) membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 55% o-nitrophenyloctyl ether (NPOE), 7% BHAB and 8% oleic acid (OA). This sensor shows very good selectivity and sensitivity towards copper ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition and pH and influence of additive anionic on the response properties of electrode were investigated. The electrode exhibits a Nernstian behavior (with slope of 29.6mV per decade) over a very wide concentration range (5.0x10(-8) to 1.0x10(-2)molL(-1)) with a detection limit of 3.0x10(-8)molL(-1) (2.56ngmL(-1)). It shows relatively fast response time, in whole concentration range (<15s), and can be used for at least 12 weeks in the pH range of 2.8-5.8. The proposed sensor was successfully used to determination of copper in different water samples and as indicator electrode in potentiometric titration of copper ion with EDTA.
ABSTRACT
A highly selective poly(vinyl chloride) (PVC) membrane electrode based on butane -2,3-dione bis(salicylhydrazonato) zinc(II) [Zn (BDSH)] complex as carrier for thiocyanate-selective electrode is reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The sensor responds to thiocyanate in linear range from 1.0x10(-6) to 1.0x10(-1)M with a slope -56.5+/-1.1mVdecade(-1), over a wide pH range of 3.5-8.5. The limit of detection of the electrode was 7.0x10(-7)M SCN(-). Selectivity coefficients determined with fixed interference method (FIM) indicate a good discriminating ability towards SCN(-) ion in comparison to other anions. The proposed sensor has a fast response time of about 5-15s and can be used for at least 3 months without any considerable divergence in potential. It was applied as indicator electrode in titration of thiocyanate with Ag(+) and in potentiometric determination of thiocyanate in saliva and urine samples.
ABSTRACT
A sol-gel electrode and a coated wire ion-selective poly(vinyl chloride) membrane, based on thiosemicarbazone as a neutral carrier, were successfully developed for the detection of Cu (II) in aqueous solutions. The sol-gel electrode and coated electrode exhibited linear response with Nernstian slopes of 29.2 and 28.1 mV per decade respectively, within the copper ion concentration ranges 1.0 x 10(-5) - 1.0 x 10(-1) M and 6.0 x 10(-6) - 1.0 x 10(-1) M for coated and sol-gel sensors. The coated and sol-gel electrodes show detection limits of 3.0 x 10(-6) and 6.0 x 10(-6) M respectively. The electrodes exhibited good selectivities for a number of alkali, alkaline earth, transition and heavy metal ions. The proposed electrodes have response times ranging from 10-50 s to achieve a 95% steady potential for Cu2+ concentration. The electrodes are suitable for use in aqueous solutions over a wide pH range (4-7.5). Applications of these electrodes for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu2+ ion using EDTA, are reported. The lifetimes of the electrodes were tested over a period of six months to investigate their stability. No significant change in the performance of the sol-gel electrode was observed over this period, but after two months the coated wire copper-selective electrode exhibited a gradual decrease in the slope. The selectivity of the sol-gel electrode was found to be better than that of the coated wire copper-selective electrode. Based on these results, a novel sol-gel copper-selective electrode is proposed for the determination of copper, and applied to real sample assays.
ABSTRACT
A salicylate PVC-based membrane (SPME) and a coated graphite membrane (SCGE) electrodes by using a new tetracoordinate organonickel complex as ion carrier were prepared. Both sensors show a Nernstian response to salicylate ions over a very wide concentration ranges (1.0x10(-5)-1.0x10(-1) M for SPME and 1.0x10(-6)-1.0x10(-2) M for SCGE) in the pH of 7.0. The best selectivities were obtained for the membrane incorporating 30% PVC, 63% plasticizer, 2% cationic additive and 5% ionophore. The electrodes possess satisfactory reproducibility, very short response time ( approximately 10 s) in the whole concentration ranges, and excellent discriminating ability for salicylate ions with respect to the most common organic and inorganic anions. The detection limits of proposed sensors are 5.0x10(-6) and 7.0x10(-7) M for SPME and SCGE, respectively. The electrodes were successfully used for determination of salicylate in biological samples.
