Optimizacija i primena gasno-difuzione protočne injekcione metode za određivanje hlorida

A selective and sensitive procedure for the fast and indirect determination of chloride by the gas-diffusion FIA method has been optimized and applied for the determination of chloride in water samples which contained different amounts of the analyte. The examined samples were: seawater, tap water and very pure water from the water-steam system of the power plant "Nikola Tesla B" in Obrenovac. Application of an amperometric detector (model LC-17A; BAS, West Lafayette, USA) enables the detection limit to be decreased down to 0.05 mu mol/dm(3) of chloride, which col responds to 35.5 pg, and adjustment of the acceptor flow rate and direction inside the gas-diffusion unit. In this way the optimized FIA system has excellent repeatability. For 5 mu mol/dm(3) it was found to be 1.11% (n = 5). The throughput of this method is 60 samples per hour.Selektivan i osetljiv postupak za brzo, indirektno određivanje hlorida gasno-difuzionom metodom otpimizovan je i primenjen za određivanje hlorida u uzorcima voda sa vrlo različitim sadržajem ove vrste: morskoj, vodi za piće i vrlo čistim vodama u sistemu voda-para TE "Nikola Tesna B" u Obrenovcu. Upotreba amperometrijskog detektora tipa LC-17A omogućava snižavanje granice detekcije na 0.05 μmol/dm3 hlorida (što za uzorak zapremine 0.2 cm3 iznosi 35.5 pg) i podešavanje brzine i smera toka u gasno-difuzionoj jedinici. Ovako optimizovan protočni sistem ima odličnu reproduktivnost. Za hloridni standard koncentracije 5 μmol/dm3 relativna standardna devijacija iznosi 1.11 % (n = 5)

Influence of rhamnolipids, produced by Pseudomonas aeruginosa NCAIM(P), B001380 on Cr(VI) removal capacity in liquid medium

Pseudomonas aeruginosa NCAIM(P), B001380, a propitious bacterial strain isolated from mineral cutting oil was identified to be chromium tolerant and a producer of biosurfactant rhamnolipid (RL) with potential application in heavy metal bioremediation. Culture growth, RL production and Cr(VI) removal capacity of the strain in the presence of 50 mg L-1 (I) and 100 mg L-1 of Cr(VI) (II) were studied. Maximum of RL production were found in the late-stationary phase at 72 h for both Cr(VI)-amended cultures: I (236 mg L-1) and II (160 mg L-1), as well as the maximum of Cr(VI) removal capacity: 70 % (I) and 57 % (II). The amount of Cr in RL preparation II was 22 mg mg-1 determined by flame atomic absorption spectroscopy (FAAS). Appearance of a new band at 914 cm-1 in infrared (IR) spectrum of RL (II) indicated a significant proof for possible coordination of CrO42-ion with RL. The effect of Cr(VI) on monorhamnolipids (RL1) and dirhamnolipids (RL2) distribution and its ratio were studied by electrospray ionization mass spectrometry (ESI-MS). An increase was observed in a RL2/RL1 ratio for II compared to control

Enzimska kinetička metoda za određivanje propranolol-hidrohlorida u farmaceutskim preparatima zasnovana na njegovom inhibitorskom delovanju na holinesterazu

Propranolol, a widely used beta-blocker, inhibits the hydrolysis reaction of enzyme cholinesterase. Measurements of the difference in rate of hydrolysis rate between uninhibited and inhibited reactions allow the development of a kinetic method for its determination. Both systems, enzyme-substrate-chromogen and enzyme-substrate-chromogen-inhibitor, were characterized through biochemical kinetic parameters (K-M, 0.326-0.330 mmol/L; V-max, 40.0-43.0 mu mol/Lmin). The inhibition type was recognized as competitive and the inhibition constant, Ki, was determined to be 22.60 mu mol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 mu mol/L, respectively. Accuracy and precision of proposed methods were tested. The proposed method showed good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.Za propranolol, često propisivani neselektivni beta blokator, utvrđeno je da inhibira reakciju enzimske hidrolize butiriltioholin-jodida, koja je katalizovana serumskom holinesterazom. Merenjem razlike u brzini osnovne i inhibitorske reakcije hidrolize u prisustvu propranolola kao inhibitora, moguće je razviti kinetičku metodu za određivanje propranolola. Oba sistema, enzim-supstrat-hromogen kao i enzim-supstrat-hromogen-inhibitor, okarakterisani su biohemijskim kinetičkim parametrima (KM, 0,326-0,330 mmol/L; Vmax, 40-42,99 μmol/L min), inhibicija je definisana kao kompetitivna i određena je konstanta inhibicije 22,60 μmol/L. Da bi se u potpunosti iskoristile sve mogućnosti predložene metode u pogledu osetljivosti, tačnosti, preciznosti i selektivnosti, optimizovani su reakcioni uslovi. Konstruisana je kalibraciona prava, izračunata odgovarajuća jednačina i određeni granica detekcije i kvantifikacije i to 0,004 i 0,0136 μmol/L, redom. Tačnost i preciznost predložene metode su ispitane za tri koncentracije propranolola u oblasti kalibracione prave (0,082-21,120 μmol/L) u pet ponavljanja. Takođe, ispitan je uticaj većeg broja supstanci koje se mogu naći u uzorku na brzinu reakcije. Optimizovana metoda je primenjena za određivanje propranolola u farmaceutskim preparatima. Tačnost predložene metode je ispitana primenom metode standardnog dodatka. Predložena metoda ima dobru osetljivost, selektivnost, jednostavna je i brza, i nadasve lako dostupna, i na taj način primenljiva u velikom broju laboratorija

The application of hydrogen-palladium electrode for potentiometric acid-base determinations in tetrahydrofuran

The application of the hydrogen-palladium electrode (H2/Pd) as the indicator electrode for the determination of relative acidity scale (Es, mV) of tetrahydrofuran (THF) and the potentiometric titrations of acids in this solvent was investigated. The relative acidity scale tetrahydrofuran was determined from the difference half-neutralization potentials of perchloric acid and tetrabutylammonium hydroxide (TBAH), which were measured by using both H2/Pd-SCE and glass-SCE electrode pairs. The experimentally obtained value of Es scale THF with a H2/Pd-SCE electrode pair was 1155 mV, and those obtained with glass-SCE electrode pair 880 mV. By using a H2/Pd indicator electrode, the individual acids (benzoic acid, palmitic acid, maleic acid, acetyl acetone, α-naphthol) and two component acid mixtures (benzoic acid + α-naphthol, palmitic acid + α-naphthol, maleic acid + α-naphthol and maleic acid + ftalic acid) were titrated with a standard solution of TBAH. In addition, sodium methylate and potassium hydroxide proved to be very suitable titrating agents for titrating of the individual acids and the acids in mixtures, respectively. The relative error of the determination of acids in mixture was less than 3%. The results are in agreement with those obtained by a conventional glass electrode. The advantages of H2/Pd electrode over a glass electrode in potentiometric acid-base determinations in tetrahydrofuran lie in the following: this electrode gives wider relative acidity scale THF, higher the potential jumps at the titration end-point and relatively fast response time; furthermore, it is very durable, simple to prepare and can be used in the titrations of small volumes. [Projekat Ministarstva nauke Republike Srbije, br.172051

Use of the sulfide minerals pyrite and chalcopyrite as electrochemical sensors in non-aqueous solutions. The potentiometric titration of weak acids in alcohols

Natural monocrystalline pyrite and chalcopyrite were examined as new indicator electrodes for the potentiometric titration of weak acids in tert-butanol and iso-propanol. The electrodes investigated demonstrated a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 48 mV per decade for pyrite in tert-butanol. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be suitable titrating agents. The response time was less than 12 s and the lifetime of the electrodes was higher than 1 year. The advantages of the electrodes are long-term stability, rapid response, reproducibility, easy preparation and low cost

Supplementary data for article: Tripkovic, T.; Charvy, C.; Alves, S.; Lolić, A.; Baošić, R.; Nikolić-Mandić, S. D.; Tabet, J. C. Identification of Protein Binders in Artworks by MALDI-TOF/TOF Tandem Mass Spectrometry. Talanta 2013, 113, 49–61. https://doi.org/10.1016/j.talanta.2013.03.071

Supplementary material for: [https://doi.org/10.1016/j.talanta.2013.03.071]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1366

Supplementary data for article: Mandić, B. M.; Vlajić, M. D.; Trifunović, S. S.; Simić, M. R.; Vujisić, L. V.; Vučković, I. M.; Novaković, M. M.; Nikolić-Mandić, S. D.; Tešević, V. V.; Vajs, V. V.; et al. Optimisation of Isolation Procedure for Pyrrolizidine Alkaloids from Rindera Umbellata Bunge. Natural Product Research 2015, 29 (9), 887–890. https://doi.org/10.1080/14786419.2014.991929

Supplementary material for: [https://doi.org/10.1080/14786419.2014.991929]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1692

Pyrrolizidine Alkaloids and Fatty Acids from the Endemic Plant Species Rindera umbellata and the Effect of Lindelofine-N-oxide on Tubulin Polymerization

The examination of the aerial parts, roots, and seeds of the endemic plant Rindera umbellata is reported in this paper for the first time. Phytochemical investigation of R. umbellata led to the isolation and characterization of ten pyrrolizidine alkaloids and eleven fatty acids in the form of triglycerides. Pyrrolizidine alkaloids 1-9 were found in the aerial parts, 7 and 8 in the roots, and 6-10, together with eleven fatty acids, in the seeds of this plant species. The structures of compounds 1-10 were established based on spectroscopic studies (H-1- and C-13-NMR, 2D NMR, IR and CI-MS). After trans-esterification, methyl esters of the fatty acids were analyzed using GC-MS. The effect of lindelofine-N-oxide (7) on tubulin polymerization was determined

Supplementary data for article: Mandić, B. M.; Vlajić, M. D.; Trifunović, S. S.; Simić, M. R.; Vujisić, L. V.; Vučković, I. M.; Novaković, M. M.; Nikolić-Mandić, S. D.; Tešević, V. V.; Vajs, V. V.; et al. Optimisation of Isolation Procedure for Pyrrolizidine Alkaloids from Rindera Umbellata Bunge. Natural Product Research 2015, 29 (9), 887–890. https://doi.org/10.1080/14786419.2014.991929

Supplementary material for: [https://doi.org/10.1080/14786419.2014.991929]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1692

Kinetic spectrophotometric method for gold(III) determination

The kinetic spectrophotometric method for Au(III) determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of methylene blue B (3,7di-(dimethyl amino)-10-dehydro-phenotiazin chloride) by ammonium peroxo-disulfate in citric buffer solution. There was the linearity of the calibration curve in the concentration range from 0.09 to 2.90 mu g ml(-1) Au(III). The relative standard deviation was 2.50% and correlation coefficient of 0.9999. The limit of detection was determined as signal to noise ratio (3: 1) and it was 5.5 ng ml(-1). The limit of quantification, based on signal to noise ratio 10: 1 was 19.25 ng ml(-1). The selectivity was tested on the basis of influence of known amounts of different ions in the reaction mixture, upon the reaction rate. Kinetic and thermodynamic parameters were reported for both catalytic and non-catalytic reactions. The method was verified by Au(III) determination in anti-rheumatic drug "Thuredon" and in human urine samples, using ICP-AES as the comparative method. As the method is accurate, reliable, quick and simple it could be useful for clinical and toxicological practice. (c) 2004 Elsevier B.V. All rights reserved