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A new, simple, rapid, sensitive and selective kinetic spectrophotometric method for Pd(II) traces determination was elaborated in this paper. It is based on the catalytic effect of palladium ions upon the oxidation of methylene blue B (MBB) by (NH4)2S2O8 (APS) in citric buffer (BUF) solution. At the working temperature of 25 C and the wavelength of 662.4 nm, the optimal conditions for palladium determination were found. RSD value was found to be 2.6 to 4.9% for the investigated concentration range of Pd(II). Limit of detection (LD) was found to be 2.0 ng cm–3 Pd(II), and limit of quantification (LQ) is 6.9 ng cm–3 Pd(II). Only the presence of Pb2+, Hg2+ and Sn2+ in the reaction mixture interferes the determination of palladium by this method, while Au3+ and Ag+ have the catalytic effect upon the reaction rate. By this method, it is possible to determine the Pd(II) traces in the concentration range of 3.3x10–8 to 1.0x10–6 g cm–3. The method was confirmed by determination of Pd(II) traces in alloy PtRhG as well as in the powder of Pt. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172051]

The aim of this study was to determine the content of elements in the parsley roots (Petroselinum crispum) of different geographic origin and estimate their possible sources applying chemometric analysis. The concentrations of 13 elements in parsley collected at 12 locations in five districts were examined. Cluster analysis (CA) separated elements into three statistical significant clusters: metalloids, heavy, and essential metals. Principal component analysis (PCA) permitted the reduction of 13 variables to three principal components explaining 82.3% of the total variance. The first component with 48.2% of variance comprises Al, Cu, Fe, Mn, Mo, Zn, and Co. Some of these metals are essential in low concentrations and their presence in plants is of lithogenic origin. Multivariate statistical analysis approach, such as PCA and CA can be used to assess the level of elements in vegetables. These methods can be used to identify sources of elements in plants too.

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.

This study describes the effects of the substituents on electrochemical behavior and antioxidant activity of the six tetradentate Schiff bases, containing ethane-1,2-diamine or propane-1,2-diamine as the amine part and pentane-2,4-dione and/or 1-phenylbutane-1,3-dione as beta-diketone, and corresponding copper(II) complexes. Cyclic voltammograms of these compounds were recorded in dimethylsulfoxide and 0.1 M sodium perchlorate as supporting electrolyte with glassy carbon as working electrode at different scan rates. The voltammograms of Schiff bases alone showed only one irreversible peak. Voltammograms recorded for complexes showed the presence of quasi-reversible processes taking place at the metal center and reversible process at the ligand part. Both steric and inductive effects of substituents and structure of imine bridge of Schiff base ligands as well as complexes were discussed. These effects appear relevant for the antioxidant activity. Antioxidant activity of the investigated compounds expressed as Trolox equivalent antioxidant capacity is also discussed. The electrochemical behavior showed a high correlation with the antioxidant activity for investigated compounds.

The most common histological variants of papillary thyroid carcinoma (PTC), classical (CPTC) and follicular (FPTC), have different diagnostic features, molecular biology, and prognosis. Matrix metalloproteinase-9 (MMP-9) endopeptidase which degrades the components of the extracellular matrix is essential in the invasive growth and metastasizing of malignant tumors. The serum copper (Cu)/zinc (Zn) ratios are sensitive diagnostic and prognostic indicators in oncology since Cu- and Zn-dependent enzymes play important roles in the genesis and the progression of tumors. The aim of this study was to examine the expressions of MMP-9 in tissues of CPTC and FPTC, as well as to determine the Cu/Zn ratios in the same samples. MMP-9 was determined immunohistochemically, and the concentrations of copper and zinc in thyroid tissue were determined by means of flame atomic absorption spectrometry. The results obtained revealed significantly higher expressions of MMP-9 in CPTC in comparison with FPTC, as well as higher Cu/Zn ratios in CPTC than in FPTC. Thus, determining MMP-9 activities and the Cu/Zn ratios could improve the accuracy of the standard histopathological diagnosis of these two types of PTC.

Propranolol, a widely used beta-blocker, inhibits the reaction of enzyme cholinesterase hydrolysis. Measurements of the hydrolysis rate differences between and inhibited reactions, allows 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 (KM = 0.326-0.330 mmol/L; Vmax = 40-42.99 ?mol/Lmin), inhibition type was recognized as competitive, and inhibition constant, Ki, was determined to be 22.60 ?mol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 ?mol/L, respectively. Accuracy and precision of proposed methods were tested. Proposed method is characterized with good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.

Polycyclic aromatic hydrocarbons (PAHs) have been considered as environmental pollutants of a great concern. Regardless of the method of quantitative analysis to be applyied, sample preparation is essential for the accurate determination of PAHs. Due to the extreme complexity of the soil samples, caused primarily by the presence of hundreds of compounds, many of them have similar physical and / or chemical properties as well as the analyzed compounds, and preparation of environmental samples for analysis is crucial for validity of the PAHs analysis. No matter which method will be applied for later analysis, sample preparation has to fulfill a number of conditions such as, adequate selectivity, efficiency, availability, easy to perform, short duration of the procedure. QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method of sample preparation is a relatively new method that uses different sorbents and solvent systems. In this paper, the possibility of application of sorbents (diatomaceous earth, clinoptilolite and carbon black), which are not usually used in QuEChERS clean-up step of sample preparation, using 3 different solvent mixtures hexane / acetone (1:1, v / v) cyclohexane / acetone (1: 1, v / v) and acetonitrile / methanol (2:1, v / v) was investigated. Standard solutions of PAHs were treated with selected sorbents and solvent systems in all combinations, and then analyzed by GC-MS method. The overall accuracy of the method varied depending of compound and used sorbent/solvent system, while precision of the method was constantly good. Highest mean recovery for all PAHs (49.22%) was recorded for clinoptilolite, hexane / acetone combination. Diatomaceous earth showed lower recoveries in comparison with clinoptilolite, with all solvent systems, while recoveries for carbon black were almost zero. Among tested sorbents, clinoptilolite was identified as good starting sorbent which characteristics could be modified with aim to achieve higher accuracy, precision and selectivity of the method, and enable its new application in analytical chemistry. Key words: PAHs, QuEChERS, sorbents, GC-MC.

Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine. Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten's constant K(M)=0.40 mmol/L, maximal reaction rate V(max)=52.2 micromol/L min, inhibition constant K(i)=0,56 micromol/L and IC(50)=1.31 micromol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20-68.25 nmol/L, which corresponds to the real sample concentrations from 0.328 to 2.730 micromol/L. The method detection and quantification limits were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70, 29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15-7.45%. Accuracy was examined by standard addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery. The method has good sensitivity, accuracy, precision and it is suitable for clinical practice.

Proteomic approach in combination with mass spectrometry demonstrates a great potential for identification of proteinaceous materials in works of art. In this study we used a linear trap quadrupole Orbitrap (LTQ-Orbitrap), a state-of-the-art mass spectrometer for parts per million accuracy analyses of peptides behind tryptic hydrolysis. After the efficiency of the proteomic method was confirmed for reference and model samples, micro-samples from historical paintings were for the first time analysed using this technique. Superior performances of the liquid chromatography–mass spectrometry approach using a LTQ-Orbitrap mass spectrometer allowed identification of egg yolk peptides in two samples from nineteenth-century Orthodox icons, indicating egg tempera as the painting technique. Accurate precursor ion masses, in the range of ±2 ppm, and retention times of tryptic peptides strengthen protein identification. Additionally, in all historical samples the presence of animal glues suggested that the ground layer was likely bound using bovine collagen. Comparing to results acquired using matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry in our previous study, here we achieved higher ion scores and protein scores, better sequence coverage and more identified proteins. In fact, a combination of the two mass spectrometric techniques provided overlapping and complementary data, related to the detection of peptides with different physicochemical properties.

Procedure for isolation of pyrrolizidine alkaloids (PAs) from Rindera umbellata Bunge plant species was optimised. Different extraction media (methanol, ethanol and sulphuric acid), concentration and volume of sulphuric acid, pH of PA solution for alkaline extraction, extraction time and techniques (maceration, ultrasonic and overhead rotary mixer assisted extraction) were investigated. The yields of six PAs (7-angeloyl heliotridane, 7-angeloyl heliotridine, lindelofine, 7-angeloyl rinderine, punctanecine and heliosupine) were monitored by GC-MS/FID. The best results for the isolation all of six PAs were obtained when the extraction was performed with 1M sulphuric acid (30mL per 1.00g of dried sample) by overhead rotary mixer during three days. Optimal pH value for alkaline extraction of PAs with CH2Cl2 was 9, and the extraction should be performed with four portions of 30mL of CH2Cl2. This procedure could be also useful for a plant sample preparation for GC and LC analyses of PAs. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3388]

Preoperative diagnosis of papillary thyroid carcinoma (PTC) comprises numerous diagnostic procedures which are mostly applicable in tertiary institutions. Normal thyroid function depends on the presence of many trace elements and copper (Cu) and zinc (Zn) are some of those. The study is based on retrospective review of 118 patients with preoperatively diagnosed benign thyroid disease (BTD) and 12 with PTC, who underwent thyroid surgery at the Center for Endocrine Surgery Clinical Center of Serbia, Belgrade, between 2010 and 2012. The objective was to evaluate concentrations of Cu and Zn in serum as possible prediction markers for PTC in patients who underwent surgery for preoperatively diagnosed BTD. Concentrations of Cu and Zn ions in serum were measured using atomic absorption spectrophotometer. Data were analyzed using methods of descriptive statistics, Anova and t-test (p

A new, simple, rapid, sensitive and selective spectrophotometric kinetic method for Ag(I) traces determination at room temperature was elaborated in this paper. It is based on catalytic effect of silver ions upon the oxidation of methylene blue B (MBB) by K2S2O8 (PPS) in citric buffer (BUF) solution. The method was confirmed by determination of Ag(I) in PbO. The obtained results were compared to those obtained by ICP-OES method and good agreement of results was found. [Projekat Ministarstva nauke Republike Srbije, br. 172051]

The present paper describes two new, simple, rapid, selective and sensitive kinetic spectrophotometric methods for Co(II) and Sn(II) determination in solution at room temperature, based on their effect on phenyl fluorone (PF) oxidation by hydrogen peroxide in ammonia buffer. The new method was elaborated for nano amounts of Co(II) determination, based on its catalytic effect on the oxidation of PF by H2O2 in the presence of citric acid (CA) as an activator. Also, the new method for micro amounts of Sn(II) determination was developed based on its inhibitory effect upon the same reaction. Comparison of the results showed that the activated catalytic reaction has better sensitivity than the inhibitory one. Methods were validated by the analyze of chemical substances and results were improved by examining the same samples by AAS method. [Projekat Ministarstva nauke Republike Srbije, br. 172051]

Aim of this work is to propose an analytical protocol for proteinaceous binder identification in paintings using tryptic peptide analysis and MALDI-TOF mass spectrometry strengthened with MALDI-TOF/TOF tandem mass spectrometry (LIFT method). Proteinaceous binders are enzymatically digested with trypsin. From each individual protein frequently occurring in binders, a specific set of peptides is releasing during enzymatic digestion giving a peptide mass fingerprint (PMF) of that particular protein. The most intensive peptide peaks in PMF were determined and annotated with their corresponding amino acid sequence by MALDI-TOF/TOF analysis and subsequent database search. Before analyzing historical painting samples, procedure was tested and optimized on several painting model samples for a reliable and efficient identification of proteinaceous materials. The method is avoiding sample manipulation as much as possible in order to reduce sample loss. Since the applied procedures led to protein identification of binding media in model samples, MALDI-TOF/TOF was for the first time applied for analysis of proteinaceous binders in old painting samples. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3500]

Honey is well known in human diet and it is considered to be one of the healthiest foods with high nutritional value. Due to the growing presence of anthropogenic contaminants, with extremely long half-life and prevalence in all environments, some of them may be present in honey. Honey samples were spiked with six pesticides which are commonly used at the time of plant's blooming, in order to develop an efficient method for preparing honey samples for LC-MS-IT analysis. Samples of honey, spiked with soultion containing mixture of six pesticides (pirimicarb, atrazine, prometrine, malation, cyprodinil and famoxadone), were treated applying SPE with Florisil and C18 cartriges, as well as liquid-liquid extraction method. Afterwards, samples were injected in the HPLC with ESI ionisation source, and IT (ion trap) mass analyzer. Methanol solution of pesticides in the same concentrations as in spiked samples, were used as blank. In spiked honey samples, after treatment with Florisil prometrine and famoxadon were detected; with C18, atrazine and prometrine; after LLE famoxedon and pirimicarb. In the specific case, as acceptable sample preparation method SPE with Florisil cartridge may be proposed, since it enables reliable identification of the most examined pesticides. Key words: honey, pesticides, liquid chromatography, mass spectrometry, solid phase extraction

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.

The present paper describes a simple, selective and sensitive kinetic method for the determination of trace amounts of Sb(III) in the presence of Sb(V) based on its inhibition effect on the redox reaction between bromate and Victoria blue 4R (V.B. 4-R) in hydrochloric acid media. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of V.B. 4-R at 596.3 nm. Optimum operating conditions regarding reagent concentrations were established. The optimized conditions yielded a theoretical detection limit of 1.30·10‒8 g cm–3 Sb(III) based on the 3S0 criterion. The method allows the determination of Sb(III) in the range of 5·10‒8 ‒ 1.1·10‒6 g cm–3. The effects of certain foreign ions the reaction rate were determined for an assessment of the selectivity of the method. The kinetic parameters of the reaction were reported, and the rate equations were suggested. The results were validated statistically and through recovery studies. The proposed method has been successfully applied to the determination of Sb(III) in various model and real samples.