Liquid chromatography — catalytic analysis detection for highly sensitive and automated fractional determination of vanadium(IV) and -(V)

Sol‐Gel Derived Potentiometric Sensor for Determination of Vanadyl Ions

“…The results obtained in the present work demonstrate that the calix [4](O 3 S 2 -crown-5)ether as a suitable ionophore can be used in the development of sol-gel electrodes. The electrodes response to the VO 2þ ions in a Nernstian fashion with low detection limit of 4.9 Â 10 À7 mol dm…”

“…A digital pH meter (Corning Model 125) was used for measuring pH. Calix [4](O 3 S 2 -crown-5)ether (TCA) was synthesized according to procedure described previously [30]. All reagents used were of analytical reagent grade.…”

“…The potential response of all the electrodes using membranes of thiacalix [4]arene of different composition based on sol-gel was investigated by varying the concentration of the test solution from 5.0 Â 10 À8 to 1.0 Â 10 À1 mol dm À3 and the results obtained are given in Table 2. As shown in Table 2, the use of 250 mL DEDMS, 90 mL TEOS, 280 mL ethanol and 80 mL HCl 0.1 mol dm À3 , in the presence of 4 mg TCA and 1 mg NaTPB, results the best response, with a Nernstian slope of 29.3 AE 0.3 mV/decade over a relatively wide concentration range of VO 2þ ions, and the best sensor was No.…”

“…From the potentiometric selectivity data presented in Figure 4, it is obvious that thiacalix [4]arene interacts relatively strongly with VO 2þ ions and can be used successfully as a sensing agent for vanadyl-selective electrodes. This behavior may be due to the lack of plasticizer into the sensing membrane [35 -37] and selective uptake of vanadyl by thiacalix [4]arene in comparison to the other species presented in Figure 4. The data in Figure 4 also show that the electrode based on sol -gel exhibits suitable selectivity for vanadyl ion over a large number of cations except Na …”

“…Hence, the development of highly sensitive and rapid methods for determination of low concentrations of vanadyl is of considerable interest. The advantageous features of thiacalix [4]arene have caused that various types of these compounds were used for the preparation of ISEs [19 -24]. The thiacalix [4]arene that we chose is shown in Scheme 1.…”