Anna Tobiasz

Application of a metal ion-imprinted polymer based on salen–Cu complex to flow injection preconcentration and FAAS determination of copper

A new Cu(II)-imprinted polymer (Cu-IIP) for preconcentration of copper by liquid-solid extraction via flow injection technique has been proposed. Cu-IIP was obtained by copolymerization of salen-Cu(II) complex with styrene and divinylbenzene using suspension polymerization technique. Granules fraction of 60-80 microm in diameter was used as a microcolumn packing. Cu(II) sorption was proved to be the most effective from solutions of pH 7, whereas similar elution effectiveness was observed when applying as eluents hydrochloric or nitric acid in the concentration range of 0.5-10% (v/v). The system exhibited good long-term stability and acid resistance. Batch sorbent capacity was found to be 0.11 mmol g(-1) of a dry polymer. Enrichment factor (EF) for 30 s loading time was 16. Preconcentration of Cu(II) and potentially interfering metal ions is strongly pH dependent. Examination of Cu(II) sorption in the presence of Pb(II), Cd(II), Zn(II) and Ag(I) showed significant influence of cadmium and zinc ions only and that was for the interferent concentrations above 0.5 mg L(-1) (Cu-IIP mass of ca. 35 mg). The interference effect was reduced with the sorbent mass increase. Fe(III) and Mn(II) ions, present in treated tap water in relatively high concentrations, did not interfere. Effective pH adjusting of the loaded solution in on-line mode, when applying diluted Clark-Lubs buffering solution, allowed accurate copper determination in tap water (compared to graphite furnace atomic absorption spectrometry, GFAAS) using standard addition or combination calibration method.

Current approaches to calibration of LA-ICP-MS analysis

For solid sample quantitative analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), the main analytical problem is the calibration step: evaluation of the function (equation) that correlates the signal with the concentration of analytes in the sample. Except for basic standards preparation, problems result from non-stoichiometric effects during vaporization, transport of ablated aerosols, atomization, and ionization in the plasma. These effects, called elemental fractionation, are mainly sample matrix dependent and thus suggest that standards used for calibration should accurately match the sample matrix. Preparation of such standards is a difficult and time-consuming process, so since the beginning of LA-ICP-MS applications for quantification of solid sample composition, different approaches have been developed to solve the problem, primarily complete matrix matching. Because the calibration of LA-ICP-MS is a key factor for its quantification capabilities, this review summarizes recent calibration approaches and related standards preparation techniques for the analysis of various solid materials by LA-ICP-MS. Selected papers concern the application of reference glasses, solution based standards, synthetic standards based on the main sample matrix component or powdered matrix certified reference materials, matrix-matched standards based on spiked sample materials, and non-matrix-matched standards, for calibration. Isotope dilution methods and signal normalization protocols used in order to improve precision are also considered.

Application of multiwall carbon nanotubes impregnated with 5-dodecylsalicylaldoxime for on-line copper preconcentration and determination in water samples by flame atomic absorption spectrometry.

The paper presents application of multiwall carbon nanotubes (MWCNTs) modified with 5-dodecylsalicylaldoxime to copper(II) flow-injection on-line preconcentration and flame atomic absorption spectrometric (FAAS) determination. Two new sorbents were obtained by impregnation of MWCNTs with Cu(II)-LIX 622(®) complex, however in the first case modification was preceded by carbon wall activation via oxidization (Cu-LIX-CNT-A sorbent), and in the second one no surface activation was performed (Cu-LIX-CNT sorbent). It was found that effective leaching of initially introduced copper and Cu(II) retained in preconcentration process could be realized with the use 7% and 5% (v/v) nitric acid, for particular sorbents. Testing the influence of loading solution pH and rate of loading on sorption it was found out that optimal range of loading solution pH was about 4.5-6.3 for activated and 6.15-6.25 for non-activated CNT. Investigation of sorption kinetics showed that the process can be described by pseudo-second order reaction model. Sorption equilibrium conditions (90% sorption) for LIX-CNT-A and LIX-CNT were obtained after 8-15min, respectively and maximum sorption capacity for the new sorbents amounted to 18.1mgg(-1) and 31.6mgg(-1), respectively. For the examined sorbents enrichment factors increased with extension of loading time up to 180s: linearly for activated and non-linearly for non-activated MWCNTs. Influence of potential interferents such as Cd(II), Zn(II), Fe(III), Mg(II) and Ca(II) ions on copper(II) sorption on the new CNT materials was examined individually and with the use of 2(5-2) factorial design. The study revealed significant interference from iron, magnesium and calcium ions at relatively high concentrations. Applicability of the proposed sorbents was tested for Cu(II) determination in various kinds of water samples and the results were compared with those obtained with the use of ICP MS as a reference technique. Copper(II) determination in two certified reference materials: waste water (EU-H-3) and ground (ES-H-2) water was performed in order to assess trueness of the evaluated preconcentration procedures. Satisfactory values of relative errors were obtained for both procedures.

Improvement of copper FAAS determination conditions via preconcentration procedure with the use of salicylaldoxime complex trapped in polymer matrix.

The paper presents application of a new resin dedicated to copper(II) flow-injection on-line preconcentration prior its flame atomic absorption spectrometric (FAAS) determination. The new sorbent, obtained by suspension polymerization technique, was styrene-divinylbenzene copolymer modified with 5-dodecylsalicylaldoxime-copper(II) complex. In flow mode leaching of initially imprinted Cu(II) ions from polymer beads was effective with 1% (v/v) nitric acid, however for elution of ions retained on the sorbent during the loading process sufficient efficiency was obtained for 0.5% (v/v) nitric acid. The most effective copper(II) sorption was observed within sample pH ca. 6.3 at flow rate 7.5mLmin(-1). Furthermore, preconcentration studies of Cu(II) ions realized in the presence of popular foreign ions like Cd(II), Pb(II), Zn(II), Ni(II), Mn(II), Co(II) did not reveal significant interference. The expected effect of Cu(II)-imprinting was confirmed by higher tolerance level for interferents ions concentration for the new sorbent than for the control polymer. It was found that alkaline metals ions and humic acid had the most relevant influence on copper(II) uptake. Accuracy of the evaluated method was assessed for analysis of water samples (tap and mineral water, river water, artesian water) and certified water reference materials compare them to results obtained by inductively plasma mass spectrometry. The satisfactory relative error values obtained with use of standard addition calibration method, confirms the feasibility of this method for Cu(II) determination in water samples. Application of 120s sorption time enabled to obtain 74-fold enrichment factor and limit of detection (3σ) equal to 0.4μgL(-1).

A standard sample preparation and calibration procedure for imaging zinc and magnesium in rats' brain tissue by laser ablation-inductively coupled plasma-time of flight-mass spectrometry

A calibration procedure consists of several steps, each of which has a significant impact on the final result of the analysis. The preparation of standard samples for analytical calibration is a far more important step in the analytical procedure than it might seem. In this paper, we have discussed a new, innovatory calibration procedure, which is itself a development of one previously published by us concerning a calibration strategy in the determination of trace elements in rat brain tissues by the laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOF-MS) method. Moreover, the article has described an important step in the preparation of standard samples, which is both an innovation and exclusive to this work. The linearity of calibration function analysis is fully acceptable (for zinc R = 0.944 and for magnesium R = 0.989), and the applied calibration method, the conventional extrapolative method (CEM), known more generally as the “standard addition method”, makes it possible to avoid interferents from the sample matrix. The results show the usefulness of the procedure developed in the presented analytical problem related to the analysis of solid biological samples. The developed research methodology enabled the preparation of distribution maps of zinc and magnesium in the rats hippocampus, which is a frontier providing unique research in the pathophysiology of a rat brain.

The influence of the starch component on thermal radical generation in flours.

Transition metal ions and radicals in flours of various botanical origins with different content of starch have been studied by EPR before and after thermal treatment. The amounts of metal ions, have been determined by ICP OES. Simulations of EPR spectra have revealed the presence of several types of radicals (carbon-centred, tyrosyl and semiquinone) localized in starch and protein fractions of flours. Thermal treatment of flours significantly increased the amount of radicals with a simultaneous decrease of the signal intensity of transition metal ions. The proposed mechanism of thermal generation of stable organic radicals was associated with the redox processes involving transition metal ions, which facilitated the formation of radicals. The dependence between the way starch is treated and the mechanism of radical formation was also shown.

Effect of selenium on distribution of macro- and micro-elements to different tissues during wheat ontogeny

Selenium (Se) is essential for health of humans, animals, and plants. Especially wheat is a major source of Se in the terrestrial food chain. In this study, an element analysis was optimized and the content of Ca, Mg, K, S, P, Fe, Se, Mn, Cu, Zn, and Mo in leaves, roots, and seeds were measured during growth of wheat (Triticum aestivum L. cv. Manu) in Hoagland nutrient solution with 5 and 15 μM Na2SeO4. Se was transported to all investigated tissues and accumulated in the seeds in proportion to used amounts. The supplementation of Se, independently of concentration, weakly modified the micro- and macro-elements content in the seedlings. In the flag-leaf stage, an increase of the Mo and S content in the shoots and the S and Cu content in the roots was found. Moreover, in the generative phase, a decrease in Ca and Fe in the roots was registered. Increased Se in the nutrient solution strongly stimulated the Se accumulation in the seeds.

Does micro- and macroelement content differentiate grains of sensitive and tolerant wheat varieties?

AbstractEnvironmental stresses are forcing breeders to produce new plant genotypes with higher resistance to stressors. Biochemical markers of stress tolerance would assist in the selection of tolerant cultivars on the early stages of plant development. The aim of these studies was to examine whether the concentration of micro and macroelements of embryos and/or endosperm could specify the wheat grains in terms of their tolerance to stress conditions. Two sensitive to drought (Radunia and Raweta), two tolerant (Nawra and Parabola) and one with intermediate tolerance (Manu) were chosen. After dividing embryos and endosperm, the microelements content (Mn, Fe, Cu, Zn and Mo) was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and macroelements (K, Ca, Mg, P and S) by inductively coupled plasma optical emission spectrometry (ICP-OES). Independent of genotype, the concentration of all elements was higher in embryos than in endosperm. In both embryos and endosperm of tolerant plants, higher content of microelements (except for Cu in embryos) was detected. The accumulation of macroelements was lower in embryos of tolerant plants (except for K), however, in the case of endosperm, higher amounts of these elements, were registered. In embryos of Manu genotype, the content of microelements was more alike to sensitive and macroelements to tolerant plants but in endosperm, the level of both micro- and macroelements was more similar to tolerant ones. It was concluded that mineral composition of wheat grains, especially those in embryos, could inform about possible resistance of genotypes to stress conditions.

Determination of Technetium-99 in Peat by Flow Injection–Inductively Coupled Plasma Mass Spectrometry

ABSTRACT Here a new flow injection system is reported for the preconcentration of technetium by solid phase extraction. The system provides analyte preconcentration, reduces interferences from polyatomic ions, and prevents interaction of concentrated nitric acid with the inductively coupled plasma mass spectrometer. The volume of eluate was significantly reduced by collecting the eluate of the highest analyte concentration in an injection loop followed by transport to the spectrometer with dilute nitric acid. Due to the absence of a suitable standard reference material, the determination of technetium in peat was compared with liquid scintillation spectrometry.

Evaluation of Manganese(II) and Manganese(VII) Speciation in Water Samples by Ion Pair High-performance Liquid Chromatography-inductively Coupled Plasma Mass Spectrometry

ABSTRACT The speciation of Mn(II) and Mn(VII) is reported by ion pair chromatography. To optimize the separation, sample pH, ion pair reagent, Mn(II) complexing agent, and composition of mobile phase were characterized. The separation of Mn(II) and Mn(VII) was performed using ethylenediamine tetraacetic acid to complex Mn(II), tetrabutylammonium hydroxide as an ion pair reagent, and a C8 column. The separation of the manganese species was demonstrated by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC ICP-MS). The conversion of Mn(VII) to Mn(II) occurred during the separation and influenced the quantification; hence, the factors affecting this process including the storage time, manganese species ratio, and sample matrix composition were evaluated and suitable calibration was demonstrated. The method was validated by characterization of the selectivity, specificity, linearity, limits of detection and quantification, repeatability, and intermediate precision. The detection limit for Mn(II) was 0.22 µg•L−1, while for Mn(VII), the value was 1.55 µg•L−1.