The Sensitivity Increase of the Potentiometric Stripping Analysis

Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR). Razvojem novih tehnika, odnosno metoda potenciometrijske striping analize (PSA), značajno je povećana osetljivost određivanja osnovne modifikacije PSA sa kiseonikom kao oksidansom. Definisane su metode za određivanje olova i kadmijuma u standardnoj elektrohemijskoj ćeliji, tankoslojnoj protočnoj ćeliji i tubulamom protočnom sistemu. Ostvarena je granica osetljivosti od 50 ng/dm3, uz reproduktivnost od oko 15%, izraženom kao koeficijent varijacije. Tačnost novih tehnika je potvrđena dobrim slaganjem rezultata analiza uzoraka pijaće vode sa rezultatima uporednih analiza izvedenih primenom osnovne modifikacije PSA, kao referentne metode. Sve analize su izvedene uz primenu kompjuterizovanog striping analizatora domaće konstrukcije i proizvodnje (Tehnološki fakultet, Novi Sad — ”Elektrouniverzal”, Leskovac).Abstract was processed by technology for Optical character recognition (OCR). А new and high sensitive techniques (methods) of the potentiometric stripping analysis аге developed. Methods for lead and cadmium determination in conventional electrochemical cell, are defined. The detection limit of 50 ng/dm3 is obtanied, by the reproducibility about 15% (CV). The ассuracу of the new techniques is confirmed by good agreements of the results of the tap water analyses, with the results obtanied from the same samples analysed by conventional PSA, as reference method. All analyses аге carried by a computerized stripping analyzer constructed and made by the Faculty of Technology, Novi Sad and ”Elektrouniverzal”, Leskovac

The Sensitivity Increase of the Potentiometric Stripping Analysis

Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR). Razvojem novih tehnika, odnosno metoda potenciometrijske striping analize (PSA), značajno je povećana osetljivost određivanja osnovne modifikacije PSA sa kiseonikom kao oksidansom. Definisane su metode za određivanje olova i kadmijuma u standardnoj elektrohemijskoj ćeliji, tankoslojnoj protočnoj ćeliji i tubulamom protočnom sistemu. Ostvarena je granica osetljivosti od 50 ng/dm3, uz reproduktivnost od oko 15%, izraženom kao koeficijent varijacije. Tačnost novih tehnika je potvrđena dobrim slaganjem rezultata analiza uzoraka pijaće vode sa rezultatima uporednih analiza izvedenih primenom osnovne modifikacije PSA, kao referentne metode. Sve analize su izvedene uz primenu kompjuterizovanog striping analizatora domaće konstrukcije i proizvodnje (Tehnološki fakultet, Novi Sad — ”Elektrouniverzal”, Leskovac).Abstract was processed by technology for Optical character recognition (OCR). А new and high sensitive techniques (methods) of the potentiometric stripping analysis аге developed. Methods for lead and cadmium determination in conventional electrochemical cell, are defined. The detection limit of 50 ng/dm3 is obtanied, by the reproducibility about 15% (CV). The ассuracу of the new techniques is confirmed by good agreements of the results of the tap water analyses, with the results obtanied from the same samples analysed by conventional PSA, as reference method. All analyses аге carried by a computerized stripping analyzer constructed and made by the Faculty of Technology, Novi Sad and ”Elektrouniverzal”, Leskovac

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 -1.0V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at -1.2V (versus Ag/AgCl (KCl, 3.5mol/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 70.0mg/L on glassy carbon electrode. The detection limits were 0.17mg/L and 0.93mg/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

Antimony film electrode for chronopotentiometric determination of insecticide imidacloprid

The most important experimental parameters were investigated for chronopotentiometric determination of imidacloprid using thin film antimony electrode as a working electrode. The film of antimony was ex-situ plated on the glassy carbon electrode. Britton-Robinson buffer pH 10 was used as an optimal supporting electrolyte, where imidacloprid provided a well define and reproductive reduction signal at the potential of -1100 mV (vs. Ag/AgCl, 3.5 mol/dm3 KCl). Based on the height and reproducibility of the analytical signal, initial potential of -0.51 V was accepted as optimal, while selected optimal ranges of reduction current were from -5 μA to -14.4 μA, and from -4.6 μA to -18.2 μA, for concentrations of 2 mg/dm3 and 10 mg/dm3 , respectively. It was determined that analytical signal of imidacloprid decreased exponentially with more negative values of reduction current. Before application of this method to environmental samples, additional experiments related to method validation are necessary

Poređenje različitih metoda za uklanjanje rastvorenog kiseonika - primena pri elektrohemijskom određivanju imidakloprida

This study compares different methods for the removal of oxygen from the solution prior to the chronopotentiometric determination of the insecticide imidacloprid on glassy carbon electrode. The research included the application of the chemical method involving addition of sulfite ion, and the physical method of purging the sample with nitrogen stream, as well as their combination. By comparing analytical signals of imidacloprid, chemical method showed almost the same efficiency as conventional physical method, while the best reproducibility was achieved by applying chemical method with addition of the saturated sodium sulfite solution. The method is very simple and can be applied for deoxygenation of the solution prior to the chronopotentiometric analysis. The application of the chemical deoxygenation significantly shortened duration of the chronopotentiometric analysis of imidacloprid from approximately 15 min to 1 min.U ovoj studiji poređene su različite metode za uklanjanje rastvorenog kiseonika iz rastvora pre hronopotenciometrijskog određivanja insekticida imidakloprida na elektrodi od staklastog ugljenika. Istraživanje je obuhvatalo primenu hemijske metode dodatkom sulfitnog jona i fizičke metode provođenje struje azota kroz uzorak u trajanju od 5, 10 i 15 min, kao i njihovu kombinaciju. Poređenjem analitičkih signala imidakloprida, hemijska metoda pokazala je skoro istu efikasnost kao i konvencionalna fizička metoda, dok je najbolja reproduktivnost ostvarena primenom hemijske metode uz dodatak 0,8 cm3 zasićenog rastvora natrijum sulfita. Metoda je veoma jednostavna i može se primeniti za uklanjanje kiseonika iz rastvora pre izvođenja hronopotenciometrijske analize. Primenom hemijske deoksigenacije značajno se skraćuje trajanje hronopotenciometrijske analize imidakloprida sa 15 min na 1 min

Polycyclic aromatic hydrocarbons in urban and rural soils of Vojvodina

Contents of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in soil samples from urban and rural areas in Vojvodina Province, Serbia. Surface soil samples were collected from 15 different locations. The samples were Soxhlet extracted, cleaned-up and analyzed using gas chromatography-mass spectrometry in the selected ion monitoring mode. The total PAHs concentrations were in the range of 0.398-1.115 mg/kg for soils from urban areas, and 0.434-0.729 mg/kg for rural soils. Comparison with the relevant maximum allowed contents proposed by the Serbian legislative indicated that the concentration of PAHs in investigated soil samples is below the levels that would require the implementation of relevant soil remediation measures

Electrochemical behavior of quercetin on boron-doped diamond electrode in different supporting electrolytes

Quercetin is one of the most abundant flavonoid compounds with a broad spectrum of health beneficial properties. In this study electrochemical behavior of quercetin on boron-doped diamond electrode as a working electrode was investigated in different supporting electrolytes. Experiments embraced 0.1 mol/L acetate buffer, citrate buffer, phosphate buffer, 0.04 mol/L Britton-Robinson buffer and 0.05 mol/L solution of HCl, while studied quercetin concentration were in the range from 2 mg/L to 30 mg/L. Voltammograms recorded in different supporting electrolytes revealed one sharp and well-defined oxidation peak of quercetin at the potential of about +0.70 V, and it was chosen for quantification of quercetin, although in some buffers one additional protracted peak was observed. In comparison to differential pulse voltammetry, square-wave voltammetry showed higher sensitivity, so this technique could be more suitable for further development. Even though high values of correlation coefficients (> 0.9900) were obtained for all studied supporting electrolytes, the best results in terms of sensitivity were observed for citrate and Britton-Robinson buffers. These preliminary results demonstrated that boron-doped diamond electrode can be used as a sensitive sensor for precise determination of quercetin in real samples

Effect of storage time on the fatty acid profile of kombucha fermented milk product

Kombucha fermented milk products are the new functional dairy products that are obtained by applying non-conventional starter culture-kombucha. The health aspect of fermented milk beverages depends on the fatty acid composition of milk fat, as one of the most important components of these products. In this investigation kombucha fermented milk product was produced from milk with 2.8% milk fat using 10% (v/v) kombucha inoculums cultivated on black tea. Effect of storage time on fatty acid profile of kombucha fermented milk product was investigated. The fatty acid composition of kombucha fermented milk product was determined after production and during 7, 14 and 21 days of storage. Fatty acids analysis was performed by capillary gas chromatography - mass spectrometry after previous extraction of lipids and derivatization. The main fatty acids encountered in kombucha fermented milk product were: palmitic, oleic, stearic and myristic with mean contents of 32.63; 26.65; 11.11 and 10.80%, respectively. During 14 days of storage content of saturated fatty acids (SFA) slightly increased, while contents of monounsaturated (MUFA) and polyunsaturated fatty acids decreased (PUFA). However, after 21 days of storage the content of SFA, MUFA and PUFA in kombucha fermented milk product was very similar with those obtained after production of fermented beverage. Results showed that the storage time has not significant influence on the fatty acid profile of kombucha fermented milk product

Deaeration method for imidacloprid determination on glassy carbon electrode.

In this work deaeration methods were investigated for chronopotentiometric determination of pesticide imidacloprid [1-(6-chloro-3-pyridyimethyl)-N-nitroimidazolidin-2-ylideneamine] on glassy carbon electrode. As a supporting electrolyte, a Britton-Robinson buffer was used. All investigations were carried out in model systems. Cathodic peak of imidacloprid could not be registered only in BrittonRobinson buffer, due to electrochemical reduction of dissolved oxygen. For this reason, it was necessary to investigate different deaeration methods for removing oxygen from the solution. Within this, deaerations by various reductants and by passing a nitrogen stream were compared. Investigated reductants were sodium sulfite, ascorbic acid, oxalic acid, potassium bromide and sodium bromide. Combinations of a certain reductant and nitrogen were compared as well. Addition of a saturated solution of sodium sulfite directly in the tested solution proved as the best deaeration method. This method provided fast deaeration step as it took less than a minute for completely removing the oxygen. An optimal concentration of the solution of sodium sulfite was also investigated. Concentrations of sodium sulfite were tested in the range of 0.6 g/idm* to 230 gidm?. Considering the height of the analytical signal and its reproducibility, concentration of 8.8 gldm? showed as optimal. This method could be applied for the determination of imidacloprid in commercial formulations and some real samples