Ljubiša M. Ignjatović

Headspace solid phase microextraction method for determination of triazine and organophosphorus pesticides in soil

A headspace solid phase microextraction method (HS-SPME) for simultaneous determination of five pesticides belonging to triazine and organophosphorus pesticide groups in soil samples was developed. Microextraction conditions, such as temperature, extraction time and sodium chloride (NaCl) content were investigated and optimized using 100 μ m polydimethyl-siloxane (PDMS) fiber. Detection and quantification were done by gas chromatography-mass spectrometry (GC-MS). Relative standard deviation (RSD) and recovery values for multiple analysis of soil samples fortified at 30 μ g kg− 1 of each pesticide were below 13 % and higher than 70 %, respectively. Limits of detection (LOD) for all the compounds studied were less than 3.2 μ g kg− 1. The proposed method was applied in the analysis of some agricultural soil samples.

Antioxidative capabilities of some organic acids and their co-pigments with malvin: Part II

Abstract Antioxidative properties of ferulic, sinapic, and tannic acids, and their co-pigment with an anthocyan molecule, malvin, were electrochemically observed by cyclic voltammetry. The values of oxidation potentials were used as a quantitative parameter in determining oxidation capabilities of the compounds. These values imply the following sequence of increasing antioxidative effect: ferulic acid

Water-soluble inorganic ions in urban aerosols of the continental part of Balkans (Belgrade) during the summer - autumn (2008)

Abstract Size-segregated aerosol samples were collected using six stages High Volume Cascade Impactor. Aerosol mass and water soluble ions concentrations were determined. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to study the origin of air masses arriving to Belgrade in the investigated period. The obtained results of aerosol mass and water-soluble ion concentrations have been divided into six sub-data sets based on air mass categories. The highest average mass concentration of the fine mode (Dp ≤ 0.49 μm) was found for air masses coming to Belgrade from the southeast and northwest directions, and of the coarse mode (3.0 < Dp ≤7.2 μm) for air masses arriving from the northwest direction. The highest concentrations of SO42– were found in the fine particles transported to the investigated area by air masses from southeast direction. The analysis of contribution of marine aerosol components (Na+ and Cl-), the Correlation and Cluster Analysis indicated the influence of marine aerosol on urban aerosol of the central Balkans coming from the Western Mediterranean and northern direction. NH4+ and SO42- and K+ dominated in the fine mode for all air mass categories. PCA demonstrated the dominant impact of secondary aerosol formation processes on urban aerosols. Graphical Abstract

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.

The dominant contribution on wet deposition of water-soluble main ions in the South-Eastern Adriatic region

AbstractThe results of content of water-soluble ions measured in 604 samples of precipitation collected in South-Eastern Adriatic region during 6 years have been analyzed. The HYSPLIT model was used to study the air mass paths. Although the ion concentrations of investigated ions in precipitation of air masses from the continental parts of Europe were significant, the total wet deposition is dominated by precipitation coming over the Mediterranean Sea. The sea salt components are significantly correlated. The correlations between Ca2+ and Mg2+, Ca2+ and SO42− and Ca2+ and K+ indicate the main terrigeneous ions.

The comparison of sample extraction procedures for the determination of cations in soil by IC and ICP-AES

This paper presents the extraction of cations from a soil sample, type ranker on serpentinite, in deionized water, by use of three different extraction techniques. The first extraction technique included the use of a rotary mixer, the second technique involved the use of a microwave digestion system with different extraction temperatures, and the third technique employed an ultrasonic bath with different extraction times. Ion chromatography was used for determining the concentration of Li, Na, K, Ca, Mg and ammonium ions in soil extracts with subsequent determination of concentrations for all cations, except for ammonium ion extraction, conducted by Inductively Coupled Plasma-Atomic Emission Spectrometry. The results of cation extractions showed that microwave assisted extraction was most efficient for the Li, Na, K, Ca, Mg, Co, Mn, Ni, Pb and ammonium ions. Use of a rotary mixer for extraction was most efficient for Cd and Zn ions, while use of ultrasound bath was most efficient for Cr, Cu, Fe and Al ions. Several times higher amount of cations extracted by the most efficient, compared to the second best technique, under optimal conditions, were noticed in the case of: Ca, Mg, Co, Mn, Fe, Al, and Zn ions.

Polarographic behaviour and determination of 1-(4'-bromophenyl)-3,3-dimethyltriazene

Abstract A study was made of the polarographic behaviour of the genotoxic substance 1-(4′-bromopheyl)-3,3-dimethlytriazene and optimum conditions were found for its determination by tast polarography and differential-pulse polarography at a static mercury drop electrode in the concentration range 1 × 10 −4 −1 × 10 −7 mol dm −3 . The results indicate that the method can be used at pH between 4.5 and6.0 for the identification and determination of the investigated substance, which is protonated without decomposition in this pH range. It was established that for the reduction of the NN group four electrons are required and the resulting products are 4-bromoaniline and dimethylhydrazine.

Experimental Design Optimization of the Determination of Total Halogens in Coal by Combustion–Ion Chromatography

Determination of total halogens in coal was investigated with oxygen bomb combustion followed by ion chromatography. Experimental parameters were optimized by fractional factorial design and response surface methodology. Fractional factorial design was employed in screening experiments to evaluate the influence of the oxygen pressure, catalyst, absorption solution, reduction reagent, bomb cooling time, and a combustion aid on the combustion of coal in an oxygen bomb. Response surface methodology was conducted to further refine the results obtained by fractional factorial design and to define parameters for the procedure. The accuracy and precision of combustion with ion chromatography were evaluated by the use of two certified reference materials and by fortified in-house coal standards. The limits of detection and quantification for total halogens were 0.84 and 2.80 milligrams per kilogram, respectively, for 500 milligram samples. Ion chromatography provided relative standard deviations less than 4 percent, recoveries exceeding 95 percent, and was convenient. This method is recommended for routine determination of total halogens in coal because of its reliability.

Adsorptive stripping voltammetric determination of 1-(4′-bromophenyl)-3,3-dimethyltriazene

The optimum conditions were established for the determination of the genotoxic substance 1-(4′-bromophenyl)-3,3-dimethyltriazene by differential-pulse voltammetry at a hanging mercury drop electrode in the concentration range 1 × 10−4 to 1 × 10−7 mol dm−3. The sensitivity of the determination can be improved through adsorptive accumulation of the investigated substance on the surface of the hanging mercury drop electrode: differential pulse adsorptive stripping voltammetry can be used in the concentration range 1 × 10−7 to 2 × 10−10 mol dm−3. The relative standard deviation (for ten determinations at 2 × 10−10 mol dm−3) was 7.5%.

Electrochemical behaviour of rosmanol 9-ethyl ether, a diterpene lactone antioxidant isolated from sage

The electrochemical behaviour and mechanism of the redox process of the natural antioxidant rosmanol 9-ethyl ether, isolated fromSaliva officinalis L., were studied. The cyclic voltammograms of rosmanol 9-ethyl ether (R9EE), at characteristic pH values, and the electrochemical parameters for all investigated pH values were measured. Three characteristic pH regions, each with different behaviour of R9EE, were identified. In regions of pH < 4 and pH > 5 only one anodic peak appeared, whereas in the solutions of pH 4–5 two anodic peaks could be noted. The overall oxidation mechanism at pH < 4 is an e.H.e.H. oxidation mechanism, which as a final product gives a quinonic molecule. The influence of pH on the second oxidation peak potential tends towards zero in accordance with the preceding dissociation of the one of phenolic groups, thus suggesting an e.e.H. mechanism at pH > 5. This means that at the pH values expected in plant cells, R9EE has an unexpected structure, making this substance a potent antioxidant. Electrochemical and spectrophotometric measurements enabled us to establish an extremely low pKa value (4.35) for R9EE.