ABSTRACT
A polymer inclusion membrane (PIM) composed of 50 wt% base polymer poly(vinylidenefluoride-co-hexafluoropropylene), 40 wt% extractant Aliquat® 336, and 10 wt% dibutyl phthalate as plasticizer/modifier provided the efficient extraction of vanadium(V) (initial concentration 50 mg L-1) from 0.1 M sulfate solutions (pH 2.5). The average mass and thickness of the PIMs (diameter 3.5 cm) were 0.057 g and 46 µm, respectively. It was suggested that V(V) was extracted as VO2SO4- via an anion exchange mechanism. The maximum PIM capacity was estimated to be ~56 mg of V(V)/g for the PIM. Quantitative back-extraction was achieved with a 50 mL solution of 6 M H2SO4/1 v/v% of H2O2. It was assumed that the back-extraction process involved the oxidation of VO2+ to VO(O2)+ by H2O2. The newly developed PIM, with the optimized composition mentioned above, exhibited an excellent selectivity for V(V) in the presence of metallic species present in digests of spent alumina hydrodesulfurization catalysts. Co-extraction of Mo(VI) with V(V) was eliminated by its selective extraction at pH 1.1. Characterization of the optimized PIM was performed by contact angle measurements, atomic-force microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis/derivatives thermogravimetric analysis and stress-strain measurements. Replacement of dibutyl phthalate with 2-nitrophenyloctyl ether improved the stability of the studied PIMs.
ABSTRACT
A diclofenac (DCF)-imprinted polymer, composed of polyaniline, reduced graphene oxide (rGO) and triphenylamine, as cross linker, was synthetized. This composite was identified by using SEM and FT-IR techniques. The prepared DCF-imprinted polymer (MIP) was used for modification of carbon paste electrodes (CPEs) to fabricate a selective DCF electrochemical sensor. Electrochemical behavior of DCF on the investigated sensor and the optimization of the parameters affecting the DCF determination were screened by cyclic voltammetry (CV). The cyclic voltammogram of DCF showed an anodic peak current at about 0.5â¯V (vs. SCE). The calibration curve for DCF determination was obtained by applying the investigated sensor as working electrode in differential pulse voltammetry (DPV). A linear increase in the anodic peak current was observed in the range 5-80â¯mgâ¯L-1 of DCF. The corresponding limit of detection was calculated to be 1.1â¯mgâ¯L-1. The relative standard deviations of the inter- and intra-day analysis of DCF presented by the method were found to be as 2.43% and 2.47%, respectively. The selectivity of the investigated sensor was evaluated by its use for determination of DCF in the binary solutions containing DCF/glucose, DCF/urea and DCF/ascorbic acid. It was shown that the fabricated electrode can be successfully used for analysis of DCF in pharmaceutical and urine samples.
