József Posta

On-line separation and preconcentration of chromium species in seawater

Abstract A study was undertaken to ascertain the analytical capabilities of combined HPLC-ICP-AES with ultrasonic nebulization or HPLC-ICP-MS systems to perform on-line separation of CrIII-CrVI and on-line preconcentration of CrVI. Tetrabutylammonium bromide was used as the ion-pair forming agent and a reverse phase C18 column was used for separation. By optimizing the conditions of separation and preconcentration as well as plasma parameters a method could be developed for the determination of CrIII and CrVI in seawater by HPLC-ICP-AES with ultrasonic nebulization. In this matrix detection limits (3σ criterion) turned out to be 4.6 ng/ml for CrIII and 3.7 ng/ml for CrVI, while the RSD is 2%–3% at the level of 100 ng/ml Cr. As the preconcentration of CrVI is regarded, the detection limit of ICP-AES depends, among others, on the sample volume loaded onto the column. It resulted to be 0.20 ng/ml for an initial volume of 2 ml, while the RSD at 10 ng/ml CrVI was ± 3.8%. On the other hand, the high salinity of seawater and C content of the separation eluent pose serious problems with ICP-MS detection. In fact, in this matrix only CrVI preconcentration was achieved with a detection limit of 0.12 ng/ml for CrVI (initial volume 2 ml). Due to isobaric interferences, the isotope at mass 50 (relative abundance 4.31%) was preferred.

A novel approach in dispersive liquid–liquid microextraction based on the use of an auxiliary solvent for adjustment of density: UV–VIS spectrophotometric and graphite furnace atomic absorption spectrometric determination of gold based on ion pair formation

This paper presents a novel approach to dispersive liquid-liquid microextraction (DLLME), based on the use of an auxiliary solvent for the adjustment of density. The procedure utilises a solvent system consisting of a dispersive solvent, an extraction solvent and an auxiliary solvent, which allows for the use of solvents having a density lower than that of water as an extraction solvent while preserving simple phase separation by centrifugation. The suggested approach could be an alternative to procedures described in the literature in recent months and which have been devoted to solving the same problem. The efficiency of the suggested approach is demonstrated through the determination of gold based on the formation of the ion pair [Au(CN)(2)](-) anion with Astra Phloxine (R) reagent and its extraction using the DLLME procedure with subsequent UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric detection. The optimum conditions were found to be: pH 3; 0.8 mmol L(-1) K(4)[Fe(CN)(6)]; 0.12 mmol L(-1) R; dispersive solvent, methanol; extraction solvent, toluene; auxiliary solvent, tetrachloromethane. The calibration plots were linear in the ranges 0.39-4.7 mg L(-1) and 0.5-39.4 μg L(-1) for UV-VIS and GFAAS detection, respectively; thus enables the application of the developed method in two ranges differing from one from another by three orders of magnitude. The presented approach can be applied to the development of DLLME procedures for the determination of other compounds extractable by organic solvents with a density lower than that of water.

On-line chromatographic separation and determination of chromium(III) and chromium(VI) with preconcentration of the chromium(III) using potassium hydrogen phthalate, in various samples by flame atomic absorption spectrometry

A method has been developed for the on-line LC separation of CrIII on a reversed-phase C18 column in the presence of potassium hydrogen phthalate, which is a recently introduced reagent for chromatography. It is much more selective for CrIII in contrast to many other complex-forming agents discussed in the literature, so that in its presence virtually no ions are sorbed onto the C18 column except for CrIII. Hence almost no interferences due to the matrix are found during the detection of CrIII. The CrIII sorbed onto the column was eluted into the flame of an atomic absorption spectrometer using a mixture of methanol and water [80–20(%(v/v))]. With 100 µl of sample solution the detection limits (3σ) were found to be 0.024 and 0.075 mg l–1 for the separation of CrIII and CrVI with FAAS detection and the period needed for separation was under 60 s. For the preconcentration of the CrIII content of a 5 ml sample solution, the detection limit (3σ) was 0.73 ng ml–1, the accuracy of the measurement was 3.8% RSD for the preconcentration of 20 ng ml–1 of CrIII. The sensitivity of the method enabled the determination of the CrIII and CrVI content of surface waters and various samples of natural origin at concentrations below ng ml–1 to be made. After reduction of CrVI to CrIII with ascorbic acid and its preconcentration, the total Cr content of various samples could be determined.

Apoptogenic and necrogenic effects of mercuric acetate on the chromatin structure of K562 human erythroleukemia cells.

Time lapse video photography was used to follow the movement of individual cells after in vitro treatment with Hg(II) acetate. Cellular changes of mercuric ions were characterized by their properties of causing reduced cellular mobility (10-50microM), and complete lack of cellular movement at higher concentrations (100-1000microM). Results show that after mercury treatment at subtoxic levels (1microM): (a) chromatin changes were the earliest signs of cytotoxicity, (b) two major parts in nuclear material of K562 erythroleukemia cells could be distinguished, highly condensed supercoiled and decondensed veil-like chromatin, (c) decondensed chromosomes were rejected as clustered puffs and (d) often the nuclear material was broken down to apoptotic bodies. Nuclear changes caused by Hg(II) acetate in the concentration range between 10 and 50microM were characterized by apoptosis seen as broken nuclei and apoptotic bodies. High concentration of Hg(2+) ions (100microM) initiated necrotic nuclear changes, with enlarged leaky or opened nuclei.

Elimination of the interfering effects of ligands in the determination of cobalt by atomic absorption spectrometry

Abstract In atomic absorption spectrometric determinations of cobalt(II) and cobalt(III), the interfering effects of different complex-forming substances can be completely eliminated by addition of excess of cyanide. Cyanide has a double role: first, it forms very stable cyano complexes, so that the cobalt species reaching the flame will normally be independent of the original composition of the solution; secondly, the high excess of cyanide produces favourable physical and chemical conditions for cobalt atomization.

A simple method of boron determination in mineral waters using Victoria blue 4R

The reaction of the tetrafluoroborate anion with Victoria blue 4R (VB4R) reagent was investigated, and a new, simple, rapid and sensitive method was developed for the spectrophotometric determination of boron. The method is based on the reaction of boric acid with fluoride, which forms the tetrafluoroborate anion, and that is followed by the extraction of with VB4R into benzene and subsequent spectrophotometric detection. The optimum conditions for the conversion of boron to tetrafluoroborate anion as well as for complex formation and extraction of with VB4R were found. The molar absorptivity of the investigated complex is 9.6 × 104 L mol−1 cm−1 at 610 nm. The absorbance of the coloured extracts obeys Beers law in the range 0.03–0.55 mg L−1 of B(III). The limit of detection calculated from a blank test (n = 10; P = 0.95) based on 3 s is 0.02 mg L−1 of B(III). Under appropriate extraction conditions, the majority of metals (excluding probably tantalum and some others) did not form extractable fluoride complexes with VB4R. Therefore, the presence of small quantities of metals should not interfere with the determination of boron in the presence of a sufficient surplus of fluoride. Exceptions, however, are metal ions such as Sn(IV), Ti(IV), Sn(II), Zr(IV), Hg(II), Hg(I), Tl(I), etc., which strongly hydrolysed under experimental conditions. Some anions formed complexes with the cation of VB4R and are easily extractable using benzene. Examples of such ions are , I−, SCN−, Br−, bromate, chlorate, iodate and perrhenate. These anions strongly interfere with boron determination and therefore must first be extracted with VB4R before boron determination. The boron must then be converted to and extracted with VB4R into benzene for determination. The Cl−, , , CH3COO− and anions are extracted in very small amounts or not at all, and do not interfere with boron determination. The reaction mechanism was also discussed. Quantum chemical calculations were carried out for VB4R, and the optimised molecular structure and atomic net charges were calculated. The possible position of the protonation of VB4R as well as the possible position for dipole-ion interaction (associate building) between the reagent and the anion was predicted. The method was used for the determination of boron in commercial brand mineral waters.

The effect of a fireworks event on the amount and elemental concentration of deposited dust collected in the city of Debrecen, Hungary

Many social celebrations in urban areas are followed by fireworks show. The organic and inorganic pollutants emitted during detonations are expected to affect the ambient air quality of these celebration sites. The environmental aspects of fireworks events are usually investigated by analyzing the concentration and composition of airborne particulate matter, while there is limited information regarding the effect of fireworks on the elemental concentration of deposited dust. In this study, foliage dust samples were collected in the city of Debrecen (Hungary) before and after the fireworks show, organized on the 20th of August for the celebration of a historical event. Leaf samples (Tilia tomentosa) were collected around the location of the area of festivities. The sampling sites were further divided into five areas: city center (center), Southeast (SE), Southwest (SW), Northeast (NE), and Northwest (NW). We found that the amount of deposited dust particles increased significantly after the fireworks show compared to the background; we also found significant differences in the amount of dust deposition between the different locations of the city. A statistically higher level of Ca, Mg, and Sr was detected in samples collected after the display compared to those collected during the previous days, while the concentration of other studied elements were not statistically different from the background level. Our study confirmed previous findings that the relatively high altitude of detonations allows chemicals to disperse in the fine and ultrafine aerosol fractions; thus, the emitted pollutants by fireworks shows do not increase the level of elements as markedly in deposited dust as in the inhalable fraction.

Relationship between Serum Nickel and Homocysteine Concentration in Hemodialysis Patients

Severe hyperhomocysteinemia (HHC) is associated with atherosclerosis. In hemodialysis (HD) patients, one of the main causes of death is cardiovascular disease. In animals, trace elements such as cobalt, copper, iron, and nickel ameliorated vitamin B12 deficiency-induced HHC. However, correlations between plasma total homocysteine (tHcy) and trace elements in HD patients have not been investigated. Therefore, tHcy, folate, vitamin B12, trace elements (cobalt, copper, iron, and nickel), and some laboratory parameters such as serum total protein, albumin, transferrin, ferritin, C-reactive protein (CRP), and interleukin-6 concentrations were determined in 122 hemodialysis patients. When patients were divided into groups according to their tHcy, we found no significant differences in concentrations of cobalt, copper, and total protein, while nickel was higher, and folate, vitamin B12, and iron were lower in patients with lower than higher tHcy. In univariate regression analysis, tHcy negatively correlated with concentrations of folate (r = −0.302, p < 0.006), vitamin B12 (r = −0.347, p < 0.0001), nickel (r = −0.289, p < 0.006), and CRP (r = −0.230, p < 0.02) and positively with serum albumin (r = 0.316, p < 0.0004) and hemoglobin (r = 0.329, p < 0.0001) values. No relationship between tHcy and serum concentrations of cobalt, copper, iron, or other laboratory parameters was found in HD patients. The effect of cobalt and nickel on homocysteine production was assessed in human peripheral mononuclear cells (PBMCs). Nickel but not cobalt at concentrations found in HD patients significantly inhibited homocysteine, cysteine, and S-adenosylhomocysteine production in human PBMCs. These results suggest that nickel might also be involved in the regulation of the methionine–folate cycle in humans, as was demonstrated in animal experiments.

Comparison between X-ray fluorescence and inductively coupled plasma atomic emission spectrometry in the analysis of sediment samples

Abstract Two multielemental analytical techniques, X-ray fluorescence analysis (XRF) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the analysis of the elemental composition of sediment samples from a marsh and standard reference materials. The sediment samples were pretreated with different methods which are widely used in practice. A comparison was made not only between the concentrations obtained by the different methods, but also between the statistical conclusions derived from the processing of the experimental results. Good agreement was found for some elements, e.g. Mn, Zn and Sr, while the concentrations and the statistical conclusions were shown to depend on the analytical method used in the case of other elements, e.g. Fe and Zr.

Separation of organic and inorganic arsenic species by capillary zone electrophoresis

SummaryCapillary zone electrophoresis has been used to separate arsenite, arsenate, dimethylarsinic acid, and phenyl-,p-aminophenyl-, ando-aminophenylarsinic acids. Identification and quantification of the arsenic species at mg L−1 levels was possible by use of direct UV detection at 200 nm. The relative standard deviation (n=7) ranged from 0.97 to 1.52% for migration times and from 2.08 to 4.31% for peak areas. A method for rapid separation of inorganic arsenic species was also developed; by use of this method arsenite and arsenate could be separated within 2 min.