Ksenija R. Kumrić

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

AbstactIn this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (Ep) of linuron oxidation in 0.1 mol dm−3 H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm−3 H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 µmol cm−3) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds.

Mass transfer resistance in a liquid‐phase microextraction employing a single hollow fiber under unsteady‐state conditions

In this study, the mass transport resistance in liquid-phase microextraction (LPME) in a single hollow fiber was investigated. A mathematical model has been developed for the determination of the overall mass transfer coefficient based on the acceptor phase in an unsteady state. The overall mass transfer coefficient in LPME in a single hollow fiber has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase. It can be achieved either using a high volume of donor to acceptor phase ratio or tuning the extraction conditions to obtain a low-enrichment factor, so that the analyte concentration in the sample is not significantly influenced by the mass transfer. Two extraction systems have been used to test experimentally the developed model: the extraction of Lu(III) from a buffer solution and the extraction of three local anesthetics from a buffer or plasma solution. The mass transfer resistance, defined as a reciprocal values of the mass transfer coefficient, was found to be 1.2 × 10(3) cm(-1) min for Lu(III) under optimal conditions and from 1.96 to 3.3 × 10(3) cm(-1) min for the local anesthetics depending on the acceptor pH and the hydrophobicity of the drug.

Surfactant modification and adsorption properties of clinoptilolite for the removal of pertechnetate from aqueous solutions

Natural clinoptilolite modified with a cationic surfactant stearyldimethylbenzylammonium chloride (SDBAC) was used as an adsorbent for the removal of pertechnetate from aqueous solutions. Adsorption studies were performed in a batch system. The effects of various experimental parameters (amount of surfactant loading, contact time, solution pH, competing anions) on the removal efficiency of TcO4− were investigated. SDBAC-clinoptilolite with organo-bilayer was successfully used to remove TcO4− from aqueous solutions in the pH range of 5.0-8.0. ReO4− as an analogue of TcO4− was used to model the isotherms. Adsorption capacity of the SDBAC-clinoptilolite and the mechanism of ReO4− (TcO4−) sorption were also determined.

Extraction of lutetium(III) from aqueous solutions by employing a single fibre-supported liquid membrane

Transport behaviour of Lu(III) across a polypropylene hollow fibre-supported liquid membrane containing di(2-ethylhexyl)phosphoric acid (DEHPA) in dihexyl ether as a carrier has been studied. The donor phase was LuCl(3) in the buffer solution consisting of 0.2 M sodium acetate at pH 2.5-5.0. A miniaturised system with a single hollow fibre has been operated in a batch mode. The concentration of Lu(III) was determined by indirect voltammetric method using Zn-EDTA complex. The effect of pH and volume of the donor phase, DEHPA concentration in the organic (liquid membrane) phase, the time of extraction and the content of the acceptor phase on the Lu(III) extraction and stripping behaviour was investigated. The results were discussed in terms of the pertraction and removal efficiency, the memory effect and the mean flux of Lu(III). The optimal conditions for the removal of (177)Lu(III) from labelled (177)Lu-radiopharmaceuticals were discussed and identified. The removal efficiency of Lu(III) greater than 99% was achieved at pH of the donor phase between 3.5 and 5.0 using DEHPA concentration in the organic phase of 0.47 M and the ratio of the donor to the acceptor phase of 182.

Indirect determination of lutetium by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode

Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA. Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically, resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL−1 lutetium could be detected after a 2 min deposition.

Removal of pertechnetate from aqueous solution using activated pyrolytic rubber char

Low-cost adsorbents, synthesized by pyrolysis of waste rubber (CR) and activated with KOH (CRA), have shown the high removal ability of

Determination of selected pesticides in environmental water by employing liquid-phase microextraction and liquid chromatography–tandem mass spectrometry

{}^{{99{\text{m}}}}{\text{TcO}}_{4}^{ - }

Simultaneous Removal of Divalent Heavy Metals from Aqueous Solutions Using Raw and Mechanochemically Treated Interstratified Montmorillonite/Kaolinite Clay

99mTcO4- from aqueous solutions in wide range of pHs (2–10) with fast adsorption rate. The Langmuir and Freundlich models suggests monolayer and multilayer adsorption of