Zvonimir J. Suturović

Determination of heavy metals in milk and fermented milk products by potentiometric stripping analysis with constant inverse current in the analytical step.

A simple and rapid method for the direct determination of cadmium, lead and copper in milk and fermented milk products by potentiometric stripping analysis (PSA) with oxygen as an oxidant and with inverse current imposed through the stripping step is described. For the more selective metals determination a samples pretreatment by the microwave acid extraction was applied. Due to the significant increase of the modified technique sensitivity, the detection limits of 0.30, 1.7 and 3.8 μg/l were obtained, for cadmium, lead and copper, respectively. The method accuracy was confirmed by analysing the standard reference material (SRM 1577 b). The contents of cadmium, lead and copper in milk samples were in the range of 2.13-4.82, 54.3-95.2 and 112.2-124.7 μg/kg, respectively, whereas in the samples of fermented milk products in the range of 6.30-24.1, 210.1-463.6 and 260.0-320.7 μg/kg, respectively.

Determination of α-tocopherol in Cosmetic Products by Chronopotentiometry

Abstract In the present study, a rapid chronopotentiometric method was developed for the determination of α-tocopherol in various cosmetic products. Determination of α-tocopherol is based on its irreverse oxidation by constant current at the planar glassy carbon electrode. The influence of the most important experimental parameters of chronopotentiometry was investigated. After optimization, an appropriate procedure for the sample preparation was developed. Under the defined experimental conditions, a detection limit of 7.5 mg L−1 of α-tocopherol was obtained. The accuracy of the defined method was confirmed by means of recovery assay. The developed method was successfully applied to quantitation of α-tocopherol in various cosmetic products.

Development and Validation of Chronopotentiometric Method for Imidacloprid Determination in Pesticide Formulations and River Water Samples

A new electrochemical method for determination of imidacloprid using chronopotentiometry on thin film mercury and glassy carbon electrode was presented. The most important experimental parameters of chronopotentiometry were examined and optimized with respect to imidacloprid analytical signal. Imidacloprid provided well-defined reduction peak in Britton-Robinson buffer on thin film mercury electrode at −1.0 V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at −1.2 V (versus Ag/AgCl (KCl, 3.5 mol/L)). The reduction time was linearly proportional to concentrations from 0.8 to 30.0 mg/L on thin film mercury electrode and from 7.0 to 70.0 mg/L on glassy carbon electrode. The detection limits were 0.17 mg/L and 0.93 mg/L for thin film mercury and glassy carbon electrode, respectively. The estimation of method precision as a function of repeatability and reproducibility showed relative standard deviations values lower than 3.73%. Recovery values from 97.3 to 98.1% confirmed the accuracy of the proposed method, while the constancy of the transition time with deliberated small changes in the experimental parameters indicated a very good robustness. A minor influence of possible interfering compounds proved good selectivity of the method. Developed method was applied for imidacloprid determination in commercial pesticide formulations and river water samples.

A simple and rapid electrochemical sensing method for metribuzin determination in tap and river water samples

This paper describes an electroanalytical method for the determination of metribuzin using a thin film mercury electrode by chronopotentiometry. Research included optimization of the most important parameters of chronopotentiometric analysis and the best responses were achieved in Britton–Robinson buffer at pH 5.0, using an initial potential of −0.21 V, ending potential of −1.1 V, and reduction current in the range from −4 μA to −15 μA. Under these conditions, metribuzin was reduced in an irreversible electrode reaction process with one well-defined reduction wave at −0.83 V (vs. Ag/AgCl, KCl, 3.5 mol dm−3). A linear response was observed for three concentration ranges 1–5, 5–15 and 15–30 mg dm−3, with an achieved limit of detection of 0.042 mg dm−3. The precision was determined as a function of repeatability and reproducibility, which showed relative standard deviation values not higher than 3.18%. Various interfering substances did not interfere with metribuzin determination. The proposed method was successfully applied to tap and river water samples. The recovery values obtained for spiked river water samples were in good statistical agreement with those obtained by the LC-MS/MS method. Accordingly, the proposed chronopotentiometric methodology can be conveniently applied in the quality control of environmental water samples as a simple, sensitive, reliable and low cost method.

Determination of polycyclic aromatic hydrocarbons in soil by gas chromatography-mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) were determined in soil samples from forty different locations in Vojvodina. The samples were Soxhlet extracted cleaned-up and analyzed using gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode (SIM). Each PAH was separately quantified using an eight-point calibration of mixed standard solutions in the range between 0.25 and 10 μg/cm3. The sum of the 16 US Environmental Protection Agency PAHs analyzed in the soil samples varied from 0.043 to 1.362 mg/kg of dry soil.