جستجوی مقالات مرتبط با کلیدواژه « liquid membrane » در نشریات گروه « علوم پایه »

The present work aimed at comparing the capabilities and efficiency of symmetric and asymmetric electrodes for potentiometric detection of Cu2+. Initially, we synthesized N-(benzothiazol-2-ylcarbamothioyl)benzamide, and 1H-NMR, 13C-NMR, and FT-IR spectroscopy approaches were used for characterization. Subsequently, it was employed as an ionophore to fabricate asymmetric electrodes of coated wire (CWE) and solid-state (SSE) and symmetric electrodes with liquid internal electrolyte (LIE). The best liquid membrane was prepared with an Ionophore: DBP: PVC: NaTPB ratio of 12:56:30:2. All electrodes exhibited Nernstian responses. The detection limits for SSE (1×10-9 mol/L) and CWE (1×10-7 mol/L) were superior to LIE (2×10-6 mol/L). Moreover, all three electrodes demonstrated very short response times (approximately 6 seconds) and exhibited large selectivity coefficient values for different cations. Asymmetric electrodes displayed longer lifetimes (SSE: 13 weeks and CWE: 12 weeks) compared to the symmetric electrode (LIE: 10 weeks). Finally, the electrodes were utilized for potentiometric titration of Cu2+ with ethylenediaminetetraacetic acid.

In the present work, N-(imidazol-2-ylcarbamothioyl)benzamide was developed and employed as an ionophore for preparing three kinds of membrane chromium(III) selective electrode including electrode with liquid internal electrolyte (LIE), solid-state electrode (SSE) and coated wire electrode (CWE). Optimal membrane composition was determined to be 2% sodium tetraphenylborate, 58% dibutyl phthalate, 10% ionophore, and 30% polyvinyl chloride, resulting in Nernstian slope behavior. Linear concentration range was 1×10-3-7×10-6 mol L-1, 1×10-3-3×10-7 mol L-1, and 7×10-3-3×10-9 mol L-1 of chromium(III) with Nernstian slope 20.76, 21.79 and 19.05 mV/decade for LIE, CWE and SSE, respectively. An improvement was note in detection limit for SSE (3×10-9 M) and CWE (2×10-7 M) in comparison with LIE (7×10-6 M). Response times were approximately 5 seconds for LIE and CWE, and 4-6 seconds for SSE. The applicable pH range for the electrodes was 3.0-5.0. SSE and CWE demonstrated longer lifetimes of about 13 and 12 weeks, respectively, compared to LIE (11 weeks). These electrodes were utilized as indicator electrodes in the chromium(III) potentiometric titration with ethylenediaminetetraacetic acid.

This paper is a continuation of the work presented in Part 1 of this series. The aim of this Part 2 is to find optimal operating condition of the process through two comparative approaches, viz. statistical approach and machine learning based model. Three important aspects of the statistical analysis, viz. descriptive, correlational and inferential statistical analyses are performed in comprehensive manner. Associated tests such as Shapiro-Wilk test and Kolmogorov-Smirnov test are conducted to check for normality. The homogeneity of variances of the dependent variable with respect to the independent variable are checked through Levene’s test. The correlational analysis are studied using Spearmann’s test and Pearson’s correlational analysis along with standard ANOVA and/or MANOVA. Based on the main effects from the test of between-subjects obtained for the variables, post hoc (Tukey HSD) analyses are computed to understand the effect of individual and combined independent variables on the dependent variables. Artificial Neural Network has been adopted in machine learning model along with Genetic Algorithm based optimization tool to compare their performances with the obtained experimental and statistical data. The data points have been divided to train, test and validate the ANN based on maximum extraction\% and recovery\% with minimum mean squared error.

4-methylcoumarin-7-yloxy-N-4-nitrophenyl acetamide and 4-methylcoumarin-7-yloxy-N-phenyl acetamide were used as effective ionophores for preparation of chromium (III) and copper (II) selective liquid membrane electrodes, respectively. Optimization of the composition of the membranes and the conditions of the analysis was performed, and under the optimized conditions the chromium (III) liquid membrane electrode has a detections limit of 1.0×10-10 with response time 4-6 s and the concentration range 1.0×10-4 to 1.0×10-10 M chromium (III) with a Nernstian slope of 20.25±0.4 mV/decade over the pH range of 4.0–7.5 and copper (II) liquid membrane electrode has a detection limit of 3.0×10-5 with response time about 5 s and the concentration range 1.0×10-1 to 3.0×10-5 M copper (II) with a Nernstian slope of 31.08±0.5 mV/decade over the pH range of 4.5–8. The chromium (III) and copper (II) selective electrodes were stable for about 8 and 5 weeks, respectively. They exhibit good selectivity for two ions. They were successfully applied for the direct determination of chromium (III) and copper (II) in wastewater and as indicator electrodes for potentiometric titration of copper ions and chromium ions with EDTA.

In this paper, 2-(4-methyl pyperazine-1-yl methyl)-1-cyano cyclohexanone was synthesized and used as an ion carrier in Cu2+ ion selective sensor. The potentiometric sensor was worked well in a concentration range of 1.0×10-2 to 1.0×10-6 M of Cu2+ ions with Nernstian slope of 30.7±0.6 mV/decade. Workable pH range of the sensor was 3.5-8.5 and the response time of the electrode was about 10 s. Detection limit of the electrode was obtained 1.0×10-6 M. The sensor has a relatively fast response time (∼10 s) and a useful working pH range of 3.5-8.5. The proposed electrode responded to copper ions selectively respect to other common metal cations. Performance of the copper electrode as an indicator electrode was checked in a potentiometric titration of Cu2+ ions with EDTA as titrant which confirmed the monitoring ability of the copper selective sensor. Finally, direct determination of Cu2+ ions in some river water samples was done to show the analytical ability of the designed sensor.

In this study, a potentiometric cobalt selective membrane sensor was prepared based on 1-(6-choloroquinoxaline-2-yl) hydrazine as a new ionophore. At first, the lowestenergy conformer of 1-(6-choloroquinoxaline-2-yl) hydrazine molecule (Ligand) and four local structure minima corresponding to their complexes with various ions were obtained using density functional theory (DFT). The calculated results of the Gibbs free energy of the reaction at B3LYP/6-31G(d) level show that the thermodynamic reactivity of complexation of cobalt ion (Co2) with studied ligand is the best. Finally, a liquid membrane electrode for potentiometric monitoring of ultra-trace amounts of Co2 was prepared by using this ligand. The electrode exhibits a Nernstian response for Co2 ion over a wide concentration range of 1.0×10-1 to 3.0×10-6 mol L-1. The limit of detection of the sensor is 1.0×10-6 mol L-1. The sensor has a relatively fast response time (~10 s) and a useful working pH range of 3.0-8.0. Interferences of some cations were also evaluated. It was used as an indicator electrode in potentiometric titration of Co2 with EDTA and in indirect determination of vitamin B12 in pharmaceutical samples. The results indicate that this electrode is sensitive for determination of Co2 and vitamin B12.

Ion potentiometric sensors are playing an important role in environmental analysis because of their simplicity and rapidity. In this study, a potentiometric liquid membrane sensor for simple and fast quantification of chromium in various samples was made. Nbanzoyl- N′(6-methyl-2-pyridyl) thiourea was selected as a sensing material in the organic phase of the PVC membrane. The wide linear range (10-6-10-1 mol L-1), low detection limit (3.0×10-7 mol L-1), and fast response time (~5 s) are the characterizations of this electrochemical sensor. The effects of some factors such as internal solution, pH, life time and selectivity were investigated. Finally, it was used for direct determination of chromium and as an indicator electrode in potentiometric titration of chromium ion.