An Ion Exchange Separation-Atomic Absorption Spectrophotometric Method for the Determination of Microgram Quantities of Copper,Iron and Zinc in Infant Milk Formula: Powder Form.

Abstract

An atomic absorption spectrophotometric method is described for the determination of microgram quantities of copper, iron and zinc in infant formula powdered milks. After sample digestion in concentrated nitric acid in a pressure vessel, the solution is evaporated till dryness, and then a solution of 6M HCl is added, in order to form the chlorocomplexes of the metals. This acid solution is passed through an ion-exchange column (anion exchange resin, chloride form). The metals are eluted from the column with diluted acid mixture of 0.005M HCl + 0.5% (v/v) HNO₃, and then the eluate is evaporated till dryness. The residue is dissolved in 1% (v/v) HNO₃, and then atomized into an air-acetylene flame. A standard addition procedure was employed as a back-up technique. The results obtained by this proposed method and those obtained by the standard addition technique were statistically treated, compared and discussed in this paper.     

An Indirect Determination of Some Ions by Flameless Atomic Absorption Using a Wire Loop Atomizer

Abstract

In previous studies using a wire loop atomizer with a preconcentrating soaking step it has been reported that there are sometimes interferences due to other species in the sample besides the metal of interest. It is possible to use this interference to advantage as an indirect method for some anions and metals that are determined only with poor sensitivity by atomic absorption spectroscopy. Cyanide, lanthanum, and zirconium were studied to determine if useful calibration curves and low detection limits could be obtained by this indirect method.     

Ionic‐liquid‐assisted microwave distillation coupled with headspace single‐drop microextraction followed by GC–MS for the rapid analysis of essential oil in Dryopteris fragrans

A rapid, green and effective miniaturized sample preparation technique, ionic‐liquid‐assisted microwave distillation coupled with headspace single‐drop microextraction was developed for the extraction of essential oil from dried Dryopteris fragrans. 1‐Ethyl‐3‐methylimidazolium acetate was the optimal ionic liquid as the destruction agent of plant cell walls and microwave absorption was medium. n‐Heptadecane (2.0 μL) was adopted as the suspended microdrop solvent in the headspace for the extraction and concentration of essential oil. The optimal parameters of the proposed method were an irradiation power of 300 W, sample mass of 0.9 g, mass ratio of ionic liquids to sample of 2.8, extraction temperature of 79°C, and extraction time of 3.6 min. In comparison to the previous reports, the proposed technique could equally monitor all the essential oil components with no significant differences in a simple way, which was more rapid and required a much lower amount of sample.     

A New Biotechnology Method of Bioelements’ Accumulation Monitoring in In Vitro Culture of Agaricus bisporus

Agaricus bisporus (J.E. Lange) Imbach is one the most popular species of edible mushrooms in the world because of its taste and nutritional properties. In the research, repeatability of accumulation of bioelements and biomass yield in experimentally chosen in vitro culture medium, was confirmed. The in vitro cultures were conducted on the modified Oddoux medium enriched with bioelements (Mg, Zn, Cu, Fe). The aim of the study was to create an effective method of sampling, which enabled non-invasive monitoring of metals concentrations changes in the medium, during increase of biomass in in vitro cultures. The first, indirect method of sampling was applied. The non-invasive probe (a dipper) for in vitro culture was used; hence, the highest biomass increase and metals accumulation were gained. The method also guaranteed culture sterility. The second method, a direct one, interfered the in vitro culture conditions and growth of mycelium, and as a consequence the lower biomass increase and metals’ accumulation were observed. Few cases of contaminations of mycelium in in vitro cultures were observed. The proposed method of non-invasive sampling of the medium can be used to monitor changes in the concentrations of metals in the medium and their accumulation in the mycelium in natural environment. Changes in concentrations of the selected metals over time, determined by the method of atomic absorption spectrometry, made it possible to correlate the obtained results with the specific stages of A. bisporus mycelium development and to attempt to explain the mechanism of sampling metals from the liquid substrate.     

One-step Bioluminescence ATPase Assay for the Evaluation of Neurotoxic Effects of Metal Ions

Summary. Membrane-bound ATPases, such as Na,K-ATPase and nucleotide triphospho-diphosphohydrolase (NTPDase), being one of the first targets of a toxic action are generally considered as good markers for estimating toxicity. A bioluminescence assay was applied for fast and sensitive evaluation of heavy metals effect on the rat brain synaptosomal membrane ATPase activity. The assay consists of ATP-consuming reaction catalyzed by synaptic plasma membrane ATPases coupled to the luminescent firefly luciferase reaction, which consumes residual ATP after the course of ATPase reaction. The bioluminescence ATPase assay was applied to study the effect of heavy and transitional metals (Cu²⁺, Pb²⁺, Cd²⁺, Hg²⁺) on rat brain ATPase activity after assay optimization. All metals applied inhibited synaptic membrane ATPase activity in a concentration dependent manner. The IC ₅₀ values (Hg²⁺ < Cu²⁺ < Cd²⁺ < Pb²⁺) obtained with the bioluminescence assay were highly correlated with those obtained by the spectrophotometric method. The fast bioluminescence ATPase assay with small sample and substrate requirements could be adjusted for high-throughput environmental and pharmacological screening.     

Spectrophotometric determination of tellurium in concentrates and brasses by chloroform extraction of the tellurium (IV) hexabromide-diantipyrylmethane complex after separations by iron collection and xanthate extraction

A method for determining 0.0001–0.10% of tellurium in copper, nickel, molybdenum, lead and zinc concentrates is described. After sample decomposition, tellurium is separated from most of the matrix elements by co-precipitation with hydrous ferric oxide from an ammoniacal medium. After reprecipitation of tellurium and iron, the precipitate is dissolved in 12M hydrochloric acid, tellurium(VI) is reduced to the quadrivalent state by heating, and separated from iron, lead and other co-precipitated elements by chloroform extraction of its xanthate. The yellow ion-association complex formed between tellurium(IV) hexabromide and diantipyrylmethane is extracted into chloroform from a 2M sulphuric acid-0.6M potassium bromide medium. The molar absorptivity of the complex is 1.82 × 10³ l.mole⁻¹.mm⁻¹ at 336 nm, the wavelength of maximum absorption. Small amounts of iron, copper and molybdenum are co-extracted as xanthates under the proposed conditions but do not cause error in the result. Interference from antimony, which is co-extracted as the chloro-complex, is eliminated by washing the extract with water. The proposed method is also applicable to brasses.     

On estimation of multivariate prediction regions in partial least squares regression

The estimation of the prediction region of partial least squares (PLS) is necessary in many engineering applications. However, research in this area focuses on the estimation of prediction intervals only. In this work, a new recursive formulation of PLS is proposed to facilitate the calculation of the Jacobian matrix of the estimated coefficient matrix. Furthermore, the computational complexity analysis indicates that the proposed algorithm is O(m²N + mpN + mpN² + mN³ + mpN⁴) per number of component. The prediction region of the multivariate PLS is obtained through local linearization. The new formulation provides one way to obtain the prediction region of the multivariate PLS. Simulation and near‐infrared spectra of corn case studies indicate the utility of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

A Polarographic Method Determing Cu(II), Cu(I) and Metallic Copper Contents in Copper Oxide Samples

Abstract

A polarographic procedure was developed which permits the analysis of powdered cupric and cuprous oxides in the presence of metallic copper. To determine CuO, Cu₂O and metallic copper content in the sample two weight aliquots were used. The first aliquot was dissolved in medium of 50 % ethanol + 3 M hydrochloric acid + saturated ascorbic acid solution. Insoluable metallic copper was determined polarographically after its' separation and additional dissolving in concentrated nitric acid.

The second sample aliquot was dissolved in 6 M hydrochloric acid and the ratio of Cu(I) / Cu(II) in the solution was determined from the polarographic curves. To calculate CuO, Cu₂O and Cu content in a sample the proposed procedure was applied. The developed method provides the accurate results of the determination of CuO, Cu₂O and Cu content in a powdered mixture. The reproducibility expressed as the relative standard deviation is from 1 % to 5 %.     

Simultaneous Titration of Ternary Mixtures of Pb(II), Cd(II) and Cu(II) with Potentiometric Electronic Tongue Detection

An automatic titration method is reported to resolve ternary mixtures of transition metals (Pb²⁺, Cd²⁺ and Cu²⁺) employing electronic tongue detection and a reduced number of pre‐defined additions of EDTA titrant. Sensors used were PVC membrane selective electrodes with generic response to heavy‐metals, plus an artificial neural network response model. Detection limits obtained were ca. 1 mg L^?1 for the three target ions and reproducibilities 3.0 % for Pb²⁺, 4.1 % for Cd²⁺ and 5.2 % for Cu²⁺. The system was applied to contaminated soil samples and high accuracy was obtained for the determination of Pb²⁺. In the determination Cd²⁺ and Cu²⁺, sample matrix showed a significant effect.     

Ultratrace Osmium,Ruthenium and Lead in Airborne Particulate Matter: Peak Area as Instrumental Datum to Improve Their Simultaneous Voltammetric Determination

Peak area as instrumental datum for determining the concentration of metals in solution instead of peak height is proposed for the simultaneous voltammetric determination in particulate matter of ultratrace Os(VIII), Ru(III) and Pb(II), species linked to vehicle emissions. In the case of species present at ultratrace concentration level or having low reversibility degree of the electrodic processes, the employment of peak area, instead of peak current, permits to achieve limits of detection lower even more of one order of magnitude. The method is based on the catalytic current of the Os(VIII)‐, Ru(III)‐ and Pb(II)‐bromate system by differential pulse voltammetry. 0.3 mol L^?1 acetate buffer pH 4.5+6.9×10^?2 mol L^?1 NaBrO₃+2.3×10^?4 mol L^?1 EDTA‐Na₂ was employed as the supporting electrolyte. For all the elements, the accuracy, expressed as relative error e%, and the precision, expressed as relative standard deviation s_r%, were satisfactory being lower than 6 %. To better validate the analytical procedure, a comparison with spectroscopic (electrothermal atomic absorption spectroscopy, ET‐AAS) is also reported.     

Flow injection determination of hydrogen peroxide using diperiodatoargentate- and diperiodatonickelate-luminol chemiluminescence

A novel chemiluminescence (CL) method for the determination of hydrogen peroxide is described. Method is based on the transition metals in highest oxidation state complex, which include diperiodatoargentate (DPA) and diperiodatonickelate (DPN) and show excellent sensitisation on the luminol-H₂O₂ CL reaction with low luminol concentration in alkaline medium. In particular, the sensitiser which was previously reported (such as Co²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Fe³⁺, Cr³⁺, KIO₄, K₃Fe(CN)₆ etc.) to be unobserved CL due to poor sensitisation with such low concentration of luminol which makes the method hold high selectivity. Based on this observation, the detection limits were 6.5?×?10^?9?mol?L^?1 and 1.1?×?10^?8?mol?L^?1 hydrogen peroxide for the DPN- and DPA-luminol CL systems, respectively. The relative CL intensity was linear with the hydrogen peroxide concentration in the range of 2.0?×?10^?8–6.0?×?10^?6?mol?L^?1 and 4.0?×?10^?8–4.0?×?10^?6?mol?L^?1 for the DPN- and DPA-luminol CL systems, respectively. The proposed method had good reproducibility with a relative standard deviation of 3.4% (8.0?×?10^?7?mol?L^?1, n?=?7) and 1.0% (2.0?×?10^?6?mol?L^?1, n?=?7) for the DPN- and DPA-luminol CL systems, respectively. A satisfactory result has been gained for the determination of H₂O₂ in rainwater and artificial lake water by use of the proposed method.     

Preconcentration and Determination of Toxic Metals by A New Calix[4]arene Bonded HPLC Column

The present study deals with the preconcentration and determination of toxic metal ions using p-tetranitrocalix[4]arene (3) appended silica-based new HPLC column. The synthesized material was characterized using Fourier transform infrared and scanning electron microscopy techniques. The sorption characteristics of the HPLC column were investigated for three toxic metals (Cd²⁺, Hg²⁺ and Pb²⁺) in column agreement. The experiments were performed in five steps that were monitored using a UV–visible diode-array detector. However, all the HPLC experimental results were reconfirmed by using atomic absorption spectrophotometer. The effect of concentration on the sorption efficiency of the column was evaluated for all the three metals and the data obtained were investigated using Langmuir, Freundlich and Dubinin–Redushkevich (D–R) sorption isotherms. The value of coefficient of determination (R ²), i.e. 0.99, suggested that the Freundlich sorption isotherm was found to be the best-fit model for all the three toxic metal ions, whereas, mean free energy was calculated from the D–R isotherm as 5.3, 5.7, and 5.8 kJ/mol for Pb²⁺, Cd²⁺, and Hg²⁺, respectively; suggesting that physical electrostatic force is involved in the sorption process. The developed method was validated for system efficiency, accuracy, and precision.

     

A Theoretical Interpretation for the Difference Between Stability Constants of the Same Metal Complex Determined by Different Analytical Methods

The ion-exchange method tends to give higher values of the stability constant than those obtained from absorption spectrophotometry for the same complex. The reason for this difference was clarified by introducing an equation for the estimation of the amount of conversion between outer-sphere and inner-sphere binding for M ^m+–L ^ℓ− complexes inside the hydration sphere of a sample metal cation.     

Rapid chromite dissolution using manganese dioxide-lithium-sulphate-sulphuric acid mixture-estimation of alumina in chromite for quality control assessment

Proposed in this paper is a less labour-intensive method involving a mixture (0.3 g MnO₂ + 1.0 g Li₂SO₄ + 10 mL H₂O + 20 mL of 36M H₂SO₄ for 0.2 g sample) to decompose chromites for accurate and precise estimation of alumina in chromite matrices for quality control (QC) assessment. Several international chromite samples, namely, CHR-BKg, CHR-Pt, IGS-30 and BCS-308 were analysed. Intermethod comparison studies reveal that the probability of results being different is less than (slight variation in case of CHR-BKg) 99% when two methods [ethylenediamine tetraacetic acid (EDTA) titration and spectrophotometry using ammonium aurinitricarboxylate (aluminon)] were compared. It also shows that the proposed method yields better results than the most conventional route involving HClO₄ decomposition used for similar purpose; hence can be used for QC programme and in the evaluation of reference materials.     

High-sensitivity Mercury Ion Detection System Using Unmodified Gold Nanorods

Hg²⁺ is one of the most universal and severe toxic metal pollutants. Here we reported a high-sensitivity and rapid method for detection of Hg²⁺. The technique was based on the localized surface plasmon resonance property of gold nanorods. Neither modification of gold nanorods nor separation of analyte was necessary. The longitudinal absorption peak of gold nanorods presented a linear blue shift as Hg²⁺ concentration increased. The blue shift of longitudinal absorption peak was due to the changes of both aspect ratio and medium dielectric constant. The sensor had a wide linear interval ranging from 285 nM to 8.00 μM, the detection limit was as low as 112 nM, and the sensitivity was 30.48 nm μM^μ1, which were comparable to the performance of the modified sensors.     

Determination of Copper and Zinc Ions by Flame-AAS After Preconcentraction Using Sodium Dodecyl Sulfate Coated Alumina Modified with 3-((1H-Indol-3-yl)-3,4,5-trimethyl)-1H-indole

A sensitive and simple method for the simultaneous preconcentration of trace amount Cu²⁺ and Zn²⁺ ions in some real samples has been established, which is based on the sorption of Cu²⁺ and Zn²⁺ on 3‐((1H‐indol‐3‐yl)‐3,4,5‐trimethyl)‐1H‐indole (ITMI) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal absorbed on the complexes was eluted using 3 mol/L nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied to content evaluation of these metals in real samples.     

Ultrasound assisted pseudo-digestion for determination of iron and manganese in citric acid fermentation mediums by electrothermal atomic absorption spectroscopy

A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples, respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction mixture of concentrated HNO₃-H₂O₂, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness, cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing the obtained results with that of conventional wet digestion method.      

Atomic Fluorescence Determination of Selenium Using Hydride Generation Technique

Abstract

Hydride generation followed by atomic fluorescence spectrometry, a simple and very sensitive technique, has been evaluated for selenium analysis in different environmental and biological samples. Research is focused on the interfering effects of several selected anions, cations, and acids on the selenium determination and the sample preparation procedures. Besides some transition metals such as Ni²⁺ Co²⁺ and Cu²⁺ HNO₃ acid, the digestion medium used for sample preparation, shows strong interference. In order to reduce this interfering effect, matrix match or standard addition is recommended. This technique is validated by analyzing a number of standard reference materials. Results for selenium analysis in some biological samples are also presented.     

Field-amplified sample injection and in-capillary derivatization for capillary electrophoretic analysis of metal ions in local wines

In-capillary derivatization and field-amplified sample injection (FASI) coupled to capillary zone electrophoresis (CZE) was evaluated for the analysis of metals (Co(II), Cu(II), Ni(II), and Fe(II)) using 2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol (Nitro-PAPS) as the derivatizing agent. For FASI, the optimum conditions were water as sample solvent, 1 s hydrodynamic injection (0.1 psi) of a water plug, 5 s of electrokinetic introduction (10 kV) of the sample. The in-capillary derivatization was successfully achieved with zone-passing strategy in order tandem injection of Nitro-PAPS reagent (0.5 psi, 7 s), a small water plug (0.1 psi, 1 s), and metal ion introduction (10 kV, 5 s). The solution of 45 mmol L^− 1 borate pH 9.7 and 1.0 × 10^− 5 mol L^− 1 Nitro-PAPS containing 20% acetonitrile was used as the running buffer. The limit of detection obtained by the proposed method was lower than those from pre-capillary derivatization about 3–28 times. The recovery of the method was comparable to pre-capillary derivatization method. In-capillary derivatization-FASI-CZE was applied to analysis of metals in wine samples. The results were compared with those obtained by CZE with pre-capillary derivatization method and atomic absorption spectrometry (AAS).