Development of methods for chronopotentiometric determination of selected pesticides in water

U okviru ove doktorske disertacije, razvijene su elektroanalitičke metode za određivanje odabranih pesticida primenom hronopotenciometrije. Ispitana je mogućnost primene elektrode od staklastog ugljenika i tankoslojne živine elektrode kao radnih elektroda za određivanje insekticida imidakloprida i herbicida metamitrona i metribuzina. U cilju optimizacije uslova hronopotenciometrijske tehnike, za svaki ispitivani sistem (pesticid/radna elektroda) ispitan je uticaj najznačajnijih eksperimentalnih parametara na analitički signal pesticida, uključujući mehanizam generisanja analitičkog signala na radnoj elektrodi (oksidacija/redukcija), optimalnu metodu za uklanjanje rastvorenog kiseonika iz analiziranog rastvora, kao i vrstu, pH i koncentraciju pomoćnog elektrolita. Nakon toga definisan je optimalni opseg potencijala i struje redukcije. Pored toga, u okviru validacije metode za svaki ispitivani sistem, ispitan je i definisan opseg linearnosti, određena granica detekcije i granica kvantifikacije, ispitana preciznost, tačnost, robusnost i selektivnost metode. Dobijeni analitički signal za ispitivane pesticide bio je posledica ireverzibilne redukcije analita na radnoj elektrodi, a za svaki analit dobijen je jedan redukcioni pik. U slučaju određivanja metribuzina eksperimenti su pokazali da se analitički signal ne može detektovati na elektrodi od staklastog ugljenika uz korišćenje dostupne instrumentacije. Ispitivanja u model-rastvorima za svaki ispitivani sistem pokazala su dobre karakteristike u pogledu preciznosti, tačnosti, selektivnosti i robusnosti metode. Najveća osetljivost za sva tri pesticida postignuta je uz primenu tankoslojne živine elektrode, a vrednosti granice detekcije iznosile su 0,17 mg/l za imidakloprid, 0,07 mg/l za metamitron i 0,04 mg/l za metribuzin. Nakon optimizacije i validacije, razvijene hronopotenciometrijske metode primenjene su na komercijalne formulacije pesticida i uzorke vode. U cilju dodatne potvrde hronopotenciometrijskih rezultata na uzorcima vode izvedena su komparativna merenja uz primenu hromatografske LC-MS/MS analize.Within this doctoral dissertation, electroanalytical methods for the determination of selected pesticides using chronopotentiometry are developed. The possibility of using glassy carbon electrode and thin film mercury electrode as a working electrode for determination of insecticide imidacloprid and herbicides metamitron and metribuzin is investigated. In order to optimize the conditions of the chronopotentiometric technique for each tested system (pesticide/working electrode), the influence of the most important experimental parameters on the analytical signal of the pesticides is investigated, including the generating mechanism of the analytical signal on the working electrode (oxidation/reduction), the optimal method for removal of dissolved oxygen from the analyzed solution, as well as type, pH, and concentration of the supporting electrolyte. Afterwards, the optimal range of potential and reduction current is defined. Additionally, within the validation of the method for each tested system, the linearity range is determined and defined, limit of detection and quantification are determined, and precision, accuracy, robustness and selectivity of the method are tested. The obtained analytical signal for the investigated pesticides is the result of irreversible reduction of the analyte on the working electrode, and for each analyte one reduction peak is obtained. In the case of metribuzin determination, the experiments have shown that by using the available instrumentation the analytical signal can not be detected on the glassy carbon electrode. Investigation in model solutions for each tested system shows good characteristics in terms of precision, accuracy, selectivity and robustness of the method. The highest sensitivity for all three pesticides was achieved by using thin film mercury electrode, and values of detection limit were 0.17 mg/l for imidacloprid, 0.07 mg/l for metamitron and 0.04 mg/l for metribuzin. After optimization and validation, the developed chronopotentiometric methods are applied to commercial pesticide formulations and water samples. In order to further confirm the chronopotentiometric results on the water samples, comparative measurements are performed using chromatographic LC-MS/MS analysis

Reproduction of the Caramote prawn, Melicertus kerathurus (Forskål, 1775) (Decapoda, Penaeidae) in Boka Kotorska bay, Montenegro (South-eastern Adriatic)

The aim of this study was to investigate for the first time some aspects of the reproductive activity of the Caramote prawn, Melicertus kerathurus, in Montenegrin waters. This species is considered a target species in the small-scale fishery in Boka Kotorska Bay, being a species of high commercial value. Sampling was carried out on a monthly basis from April 2019 to December 2019 by trammel nets. The spawning season was estimated based on monthly changes in the gonadosomatic index, condition factor and gonadal maturity stages. The main spawning season for females extends from April-May to September, with a clear peak in June. The total sex ratio (males/females) was 1:1. Sexual differences related to the length-weight relationship were noted

Primary prevention of cerebrovascular diseases

Introduction: Prevention represent the turning point in medicine, and if we have knowledge about it for long time, it isn't completely applicable, because of the fact that man kind aren't completely developed consciousness about influence of preventive measures on their health. We must learn people about preventive measures to live healthy, to feed themselves healthy, to haven't bad habits which disturb health, to avoid stress situations... The Aim of research: Establish in which extent are people on the area of general practice institution of town Sabac introduced about risk factors which leads to cerebrovascular diseases and what to do to avoid development of risk factors. Materials and methods: Research conducted in General practice institution of town Sabac in December 2011 on sample of 30 examinee. Persons are accidently selected. The data were obtained descriptive method and method of survey. The instrument used in this research is questionnaire. Results: Based on the research it provided information that examinee are mainly under the stress, that they suffer from hypertension, they have obesity, not properly take food, physically not active... but most of them normally goes to their medical examination and have wish to find out more about prevention of cerebrovascular diseases. Discussion: Nurses must trough their work seized more their users of their services and motivate them to have normally medical examination and take care of their health condition, to eliminate risk factors and cure diseases that they have already. Conclusion: Cerebrovascular diseases have huge social-medical importance. Excepting that cerebrovascular diseases are diseases with large-scale of death rate, equally is important fact that this neurological illness with large-scale disability and dramatically disorder life in family and patients surounding, and present material weight for social community. These facts highlights importance of prevention of cerebrovascular diseases

Reproduktivne značajke srdele, Sardina pilchardus (Walb, 1792), u Boki Kotorskoj (Crna Gora, južni Jadran)

The annual alteration of gonad morphology in sardine (Sardina pilchardus, Walbaum 1792) caught in the period from November 2006 to October 2007 using beach seines in the region of Boka Kotorska Bay (Montenegro, southern Adriatic) was studied. Samples were taken in the middle of each month. Total length of individuals ranged from 8.7 to 14.7 cm and weight ranged from 4.67 to 22.61 g. Their gonads were extracted and weighed, and a piece of gonad tissue was sampled for histological analysis. The length–weight relationship of all sardine specimens was described by the equation: W=0.0059 LT3.0891; (r2 = 0.963). The lowest gonadosomatic index (GSI) values, below 1, were found in June, July and August, corresponding to the state of gonad rest. The GSI increased gradually from September and October and reached its highest value in February, at 5.22 for females and 6.58 for males. After February the GSI started to decrease throughout March (4.5), April (2.4) and May (2.4). In June all gonads had a GSI bellow 1. Although primary oocytes (stage I) were present during all months, their percentage increased from May and was the highest during the summer months (June-September 100%). Mature stage IV oocytes were recorded from November to April, with the highest percentage recorded during January (26.7%). An increase in the percentage of oocytes in the yolk vesicle (II) and yolk (III) stages occurred in October, remaining almost unchanged until May. During the summer months (May – September), only stage I spermatogonia were present in the testicles. In October, spermatocytes (stage II) started to appear, while from November the spermatids (stage III) appeared as well. Spermatozoa (stage IV) appeared in December and reached their maximum level in January and February.Istraživana je godišnja promjena morfologije gonada kod srdele (Sardina pilchardus Walbaum 1792) ulovljene obalnom mrežom potegačom u razdoblju od studenog 2006. do listopada 2007. na području Bokokotorskog zaljeva (Crna Gora, južni Jadran). Ukupna dužina primjeraka kretala se od 8.7 do 14.7 cm, a težina od 4.67 do 22.61 g. Obavljena je histološka analiza gonada. Dužinsko– težinski odnos za sve jedinke može se opisati jednadžbom: W=0.0059 LT 3.0891 (r2 = 0.963). Najniže vrijednosti gonadosomatskog indeksa (GSI) utvrđene su u lipnju, srpnju i kolovozu, što odgovara stadiju mirovanja gonada. GSI vrijednosti su se postupno ovećavale u rujnu i listopadu te dosegle najviše vrijednosti u veljači 5.22 za ženke, odnosno 6.58 za mužjake. Nakon veljače, GSI vrijednosti su opadale, kroz ožujak (4.5), travanj (2.4) i svibanj (2.4). U lipnju su GSI vrijednosti bile manje od 1. Iako su primarne oocite bile prisutne u svim mjesecima, njihova zastupljenost je počela rasti u svibnju i dosegla najvišu vrijednost u ljetnim mjesecima (100% u razdoblju od srpnja do rujna). Zrele oocite u stadiju IV zabilježene su od studenog do travnja, sa najvišom zastupljenošću u siječnju (26.7%). Povećanje postotka oocita u stadijima II i III uočeno je u listopadu i ostaje gotovo nepromijenjeno do svibnja. Za ljetnjih mjeseci (svibanj–rujan), u testisima su bili prisutni samo spermatogoniji stadija I. U listopadu se započinju pojavljivati spermatociti (stadij II), a od studenog i spermatidi (stadij III). Spermatozoi (stadij IV) se javljaju u prosincu, a najvišu razinu dostižu u tijekom siječnja i veljače

Određivanje sadržaja metribuzina u formulacijama pesticida primenom elektroanalitičke metodologije

The work presents results of the determination of metribuzin content in commercial pesticide formulations by applying chronopotentiometry with thin film mercury electrode as an electrochemical sensor. In the analyzed pesticide formulations, a single well defined reduction peak of metribuzin is observed at the potential around -880 mV. The content of the herbicide in commercial formulations is determined using the calibration curve method, by applying the initial potential of -0.21 V, and the final potential of -1.10 V. Recovery values based on the declared and found content of the active ingredient are in the range from 100.67% to 101.68%, with the values of relative standard deviation lower than 1.00%, indicating high accuracy and precision of the presented method

Odgovor korovskih populacija i gajenih useva na prisustvo glifosata

Measuring amount of shikimate and chlorophyll content of hybrids of maize, line of soybean, C. canadensis and L. rigidum populations were examined after application of 1 kg a.e. ha-1 of the herbicide product TOUCHDOWN® [active ingredient: glyphosate trimesium salt (syn. sulfosate), 500 g L-1]. Samples collected 2, 4 and 6 day after treatment. Changes in amount of shikimate in treated plants vs control were significant for S plants and nosignificant for R plants. Content of chlorophyll in tretaed plants were statisticaly lower vs nontreated plant in every tested poulations/lines/hybrids, except in hybrids of maize (differences were not significant).Merenje sadržaja šikiminske kiseline i hlorofila kod hibrida kukuruza, linija soje, populacija C. canadensis and L. rigidum je obavljeno nakon primene 2 kg a.m. ha-1 herbicida TOU­CHDOWN® [aktivna materija: glifosat trimezijum so (sin. sulfosat), 500 g L-1]. Uzorkovanje je urađeno 2, 4 i 6 dana posle primene. Promene sadržaja šikiminske kiseline kod tretiranih biljaka u odnosu na ne tretirane su bile značajne kod svih S biljaka i nisu imale značaja kod R biljaka. Sadržaj hlorofila kod tretiranih biljaka je statistički bio niži u odnosu na sadržaj kod ne teretiranih biljaka kod svih testiranih populacija/linija osim kod hibrida kukuruza (razlike nisu bile statistički značajne)

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

Razmnožavanje brgljuna, Engraulis encrasicolus (Linnaeus, 1758) u Bokokotorskom zaljevu (Crna Gora, južni Jadran)

The annual alteration of gonad morphology in anchovy, Engraulis encrasicolus (Linnaeus,1758), caught in the period from July 2006 to June 2007 using beach seines in the region of Boka Kotorska Bay (Montenegro, southern Adriatic) was studied. Samples were taken each month. Total length of individuals ranged from 6.6 to 12.2 cm, while weight ranged from 1.58 to 11.27 g, Their ovaries were extracted and weighed, and a piece of female gonad tissue was sampled for histological analysis. The length–weight relationship of all anchovy specimens was described by the equation: (W = 0.0032) (L_T^3.2537; (r^2 = 0.9528)). The lowest GSI values were found in November and remained at low levels until April, which corresponded to the gonad rest stage. The GSI increased gradually during April and May, which coincides with the begining of spawning period. Although primary oocytes (stage I) were present during all months, their percentage increased from October and was the highest during the winter months (November-March 100%). Mature cells, stage IV, were present during April – October period, with highest value in May when they comprised 12.3% of total oocyte number. An increase in the percentage of oocytes in the yolk vesicle (II) and yolk (III) stages occurred in April, remaining almost unchanged until October. Smallest average oocyte size was noticed in period November – February with an average of 59.69 μm, while greatest size was recorded in April 2007, 185.84 μm.U radu su predstavljeni rezultati proučavanja godišnje promjene morfologije gonada kod brgljuna, Engraulis encrasicolus (Linnaeus, 1758) uhvaćenog obalnim mrežama potegačama u razdoblju od srpnja 2006 do lipnja 2007na području Bokokotorskog zaljeva (Crna Gora, južni Jadran). Uzorci inćuna uzimani su mjesečno, sredinom mjeseca. Ukupna dužina jedinki kretala se od 6,6 do 12,2 cm, dok je masa jedinki kolebala od 1,58 do 11,27 g. Kod ženki, jajnicima je nakon vađenja izmjerena masa, a dio tkiva jajnika odvojen za histološku analizu. Dužinsko-maseni odnos svih jedinki brgljuna opisan je jednadžbom (W = 0.0032) (L_T^3.2537; (r^2 = 0.9528)). Najniža vrijednost gonadosomatskog indeksa (GSI), manja od 1, zabilježena je u studenom, a ostala je niska sve do travnja, što odgovara razdoblje odmora gonada. GSI se postupno povećava tijekom travnja i svibnja, što se poklapa sa početkom perioda mrijesta. Iako su primarni oociti (stadij I) bili prisutni u svim mjesecima, njihova postotna zastupljenost u porastu je od listopada, a najviša tijekom zimskih mjeseci (u razdoblju od studenog do ožujka zastupljenost je iznosila 100%). Zrele stanice (stadij IV) bile su prisutne u razdoblju od travnja to listopada, sa najvećom zastupljenošću u svibnju, kada su činile 12,3% ukupnog broja oocita. U travnju se javlja povećanje postotne zastupljenosti oocita u stadijima žumanjčane kesice (II) i žumanjca (III) i ostaje gotovo nepromijenjeno do listopada. Najmanja prosječna veličina oocita zabilježena je tijekom razdoblja od studenog do veljače, kad je iznosila 59.69 μm, dok je najveća zabilježena u travnju 2007., 185.84 μ

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