Sanda Rončević

Kinetics of zeolite dissolution: Part 1. Dissolution of zeolite A in hot sodium hydroxide

Kinetics of dissolution of zeolite A in 1 m and 2 m NaOH solutions, at 338, 343, 348, and 353 K, were studied by (i) measuring the change in concentration of Si and Al in the liquid phase, (ii) determining of the stage of polycondensation of silicate anions in the liquid phase, (iii) following the change in particulate characteristics of the suspended zeolite A, and (iv) phase analysis of the solid during the dissolution. The results obtained were analyzed and discussed in accordance with known theories of dissolution, taking into account the chemical and structural characteristics of zeolites.

Kinetics of zeolite dissolution. Part 2. Dissolution of zeolite X in hot sodium hydroxide solutions

The kinetics of dissolution of zeolite X in 2 m NaOH solutions, at 338, 343, 348, and 353 K, were studied by (i) measuring changes in the concentrations of Si and Al in the liquid phase, (ii) determining of the stage of polycondensation of silicate anions in the liquid phase, (iii) following the changes in the particulate characteristics of the suspended zeolite A, and (iv) phase analysis of the solid during the dissolution. The results obtained were analyzed and discussed in accordance with the model of growth and dissolution proposed by Davies and Jones, taking into account the chemical and structural characteristics of zeolite X.

Kinetics of zeolite dissolution: Part 3. Dissolution of synthetic mordenite in hot sodium hydroxide solutions

Abstract The kinetics of dissolution of synthetic mordenite in 1 m NaOH solution at 338, 343, 348, and 353 K were studied by following the changes in the characteristics of the solid and the liquid phase during the dissolution. Various experimental techniques such as ICP spectroscopy, FTi.r. spectroscopy, X-ray diffractometry, and particle-size distribution measurement were used for this purpose. The results obtained were analyzed and discussed in accordance with the model of growth and dissolution proposed by Davies and Jones, taking into account the chemical and structural characteristics of synthetic mordenite.

Effects of low acetic acid concentrations in inductively coupled plasma atomic emission spectrometry

The effects of low acetic acid concentration on selected analytical lines (Mn II, Li I, Cu I, Cu II, Cd I and Cd II) were studied as a function of incident power and carrier gas flow rate, using an ARL 35000 C inductively coupled plasma spectrometer. Line intensity and line-to-background intensity ratios were measured for water and for 3 and 10% acetic acid. The magnitude and mechanism of interference produced by acetic acid were revealed from measured changes in the solution uptake rate, the departure of the ratio of line intensity in acetic acid solution and that in water from unity and the changes in ion-to-atom line intensity ratio. Trace metal determination in 3% acetic acid, used as a ‘model’ solution in health control of packing materials, and in 9–10% vinegar was carried out by direct aspiration of sample into the plasma at compromise conditions for multi-element analysis (r.f. power, 1200 W and carrier gas flow rate, 0.9 l min–1, using matrix-matched calibration standards. Detection limits and relative standard deviation values for Fe, Cu, Cr, Ni, Pb, Al, Cd and Zn were almost equal for aqueous solution and solutions of 3 and 10% acetic acid.

Tin Content Determination in Canned Fruits and Vegetables by Hydride Generation Inductively Coupled Plasma Optical Emission Spectrometry

Tin content in samples of canned fruits and vegetables was determined by hydride generation inductively coupled plasma atomic emission spectrometry (HG-ICP-OES), and it was compared with results obtained by standard method of flame atomic absorption spectrometry (AAS). Selected tin emission lines intensity was measured in prepared samples after addition of tartaric acid and followed by hydride generation with sodium borohydride solution. The most favorable line at 189.991 nm showed the best detection limit (1.9 μg L−1) and limit of quantification (6.4 μg kg−1). Good linearity and sensitivity were established from time resolved analysis and calibration tests. Analytical accuracy of 98–102% was obtained by recovery study of spiked samples. Method of standard addition was applied for tin determination in samples from fully protected tinplate. Tin presence at low-concentration range was successfully determined. It was shown that tenth times less concentrations of Sn were present in protected cans than in nonprotected or partially protected tinplate.

ICP-AES analysis of metal content in shell of mussel Mytilus galloprovincialis from Croatian coastal waters.

Metal content in samples of shell of mussel Mytilus galoprovincialis was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficiency of conversion of crude samples into solution by acid digestion in an open plate and in a microwave oven was examined by use of certified reference material of marine sediment and laboratory made standards of calcite and aragonite. Influence of high Ca content matrix on emission intensities of Al, Ba, Cd, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sr and Zn was observed as depression of emission signal for most of the measuring elements, ranging from 0.8% to 8%. Greater values were noted at Ba and Ni emission lines. Enhancement of signals was observed for Na and Mg lines. The determination of As, Sb, Se and Sn was performed by HG/ICP-AES. The greater abundance of Sn was found in samples collected near the Al-processing industry centre. No detectable concentrations of As, Sb, and Se were found in shell samples. Results of ICP-AES metal analysis showed that samples collected near harbours, city waste or sewage outlets, and chemical industry centres indicate the certain level of contamination. It is shown that shell analysis provides useful data in determination of marine environment status.

Tetrakis­(tetra­methyl­ammonium) dodeca-μ-chloro-hexa­chloro-octahedro-hexatantalate chloride

The title compound, (C(4)H(12)N)(4)[Ta(6)Cl(18)]Cl, crystallizes in the cubic space group Fm-3m. The crystal structure contains two different types of coordination polyhedra, i.e. four tetrahedral [(CH(3))(4)N](+) cations and one octahedral [(Ta(6)Cl(12))Cl(6)](3-) cluster anion, and one Cl(-) ion. The presence of three different kinds of Cl atoms [bridging (mu(2)), terminal and counter-anion] in one molecule makes this substance unique in the chemistry of hexanuclear halide clusters of niobium and tantalum. The Ta(6) octahedron has an ideal O(h) symmetry, with a Ta-Ta interatomic distance of 2.9215 (7) A.

Elemental Composition and Chemometric Characterization of Pyrethrum Plant Materials and Insecticidal Flower Extracts

The elemental composition of native and cultivated pyrethrum plants (Tanacetum cinerariifolium) and their insecticidal extracts obtained from dried flower heads was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The accuracy of the analytical procedure which included pressurized digestion of plant samples in HNO3/H2O2 was tested by certified reference materials. Acceptable recoveries (90–110%) for the majority of elements were obtained measured in a simultaneous multi-element mode. The total pyrethrins content was determined by HPLC and it was 2.09% for cultivated plants and 1.58% for native species. The concentrations of 18 elements and pyrethrin content were subjected to statistical multivariate analysis which showed different patterns among plant parts. The roots were characterized by a combination of loadings of iron, aluminum, nickel, chromium, strontium, and barium, while the stems, leaves, and flowers showed more contributions from sodium, potassium, calcium, magnesium, phosphorus, sulfur, manganese, and copper. A higher loading of pyrethrins was the main characteristic of dried flower extracts. It was also observed that microelements such as copper, aluminum, and iron were more readily transferred into natural insecticide extracts.

Trace Metals in Fish Biominerals as Environmental Indicators: Handheld XRF Analyses

The parts of jawbones and selected teeth (malleolus) of adult marine benthic fish Sparus aurata and Diplodus sargus was collected from different station during east Adriatic coast (Croatia). Biominerals were prepared for three different instrumental analyses: elemental analysis by X-ray Fluorescence (XRF) and inductively coupled plasma spectroscopy (ICP-AES); mineralogical analysis by X-ray diffraction (XRD).The XRF results showed major and traces elements incorporated in the fish teeth. The concentration of zinc (Zn) expressed in mg kg-1 in the enamel - outside part of the malleolus dental surface (teeth crown) varied from 77 up to 1.975 in both fish species. In the root of the same teeth samples of Zn concentration was lower and amounted from 77 - 153 mg kg-1. Contrary, maximal amount of strontium (Sr) was registered in the teeth root from 801 – 1.310 mg kg-1, and in the enamel 476 – 1.104 mg kg-1 respectively. Multivariate statistical analysis based on the Statistica 6.0. PCA has been used to determine differences among elemental composition of the major and trace elements in teeth enamel (crown) and teeth roots, and in examining correlation among incorporated elements and environmental characteristics of the sampling localities.The XRD patterns of both fish jawbones and malleolus teeth showed characteristic hydroxyapatite lines (HAP). The HAP lines of the fish jawbones are broadened and shifted on the higher angles, indicating that mandible and maxilla biominerals are not fully formed and that mineralization of the fish jawbones is a dynamic process that last permanently during organism growth.Selected elements contents Ni, Co, Fe, Cu, and Cr (expressed in mg kg-1) of bulk fishbone samples was determined by ICP-AES analysis. Investigated metals showed higher values in the teeth than in the fish jawbones. The results revealed the distribution of the heavy metals in teeth to be Fe > Cr > Cu > Ni > Co, and in the jaws Fe > Cr > Cu > Ni > Co.The purpose of this study was to investigate the possibility of using XRF for the routine determination of heavy metals in the fish biominerals, in biomonitoring studies and ecological evaluation of the environment. The over-all data obtained indicated that XRF and ICP-AES showed good agreement for the determination of the heavy metals in test samples and that XRF could be used as cost effective method of accurately and precisely determining heavy metals content of the biomineral, while drastically reducing analysis time for initial sample preparation.

Determination of chemical composition of pottery from antic Siscia by ICP-AES after enhanced pressure microwave digestion

This study describes the results of chemical characterization of archaeological pottery excavated at Sisak, Croatia known as prehistoric town Segestica (IV–I century BC) or Siscia, the capital of Roman province Pannonia Savia (I–IV century AD). Chemical composition of pottery shards and a sample of raw clay material was determined by ICP-AES analysis after high pressure microwave digestion. High efficiency of the applied system allows decomposition of ceramics by the use of nitric acid exclusively. All shards excavated from prehistoric, Early-Roman and Roman strata were decomposed without additional load of hydrofluoric acid. The accuracy of the performed procedure was tested by certified reference materials of medium and high silica content. The obtained results of sixteen element concentrations were in good agreement with certified values. Measured concentrations of main, minor and trace elements were subjected to univariate and multivariate statistical analyses. Based on principal component analysis and clustering of data, a grouping of samples in four clusters was established. The results of chemical analysis of ceramic products were found to be comparable to archaeological interpretation that denotes differentiation between local production and imported goods.