Simultaneous determination of hydride (Se) and non-hydride-forming (Ca,Mg, K,P, S and Zn) elements in various beverages (beer,coffee, and milk), with minimum sample preparation,by ICP–AES and use of a dual-mode sample-introduction system

A method has been developed enabling direct analysis (i.e. after dilution only) of beer, instant coffee, milk, and milk powder by ICP–AES. Analysis of the beverages after dilution with a low concentration of HNO₃ was used for accurate determination of essential minor and trace elements (Ca, Mg, K, P, S, and Zn). Selenium, introduced as the hydride, was determined simultaneously with the other non-hydride-forming elements using the commercial multi-mode sample-introduction system (MSIS). To obtain accurate results, however, some simple pre-treatment was needed. Analysis was also performed after microwave-assisted decomposition of the samples. Three different modes of sample-preparation, i.e. dilution only, partial decomposition (aqua regia treatment), and complete decomposition were compared. The results obtained by use of the three different sample-preparation methods were in very good agreement. Results from analysis of certified reference material (SRM 1459 non-fat milk powder) also verified the accuracy of the methods. The limit of detection obtained for Se using dual-mode sample introduction was 0.5 ng mL^–1, which corresponds to approximately 2 ng g^–1 in beer and approximately 4 ng g^–1 in coffee and milk when using the recommended procedure.     

Freon (CHF<Subscript>3</Subscript>)-assisted atomization for the determination of titanium using ultrasonic slurry sampling–graphite furnace atomic absorption spectrometry (USS–GFAAS): a simple and advantageous method for solid samples

A simple and advantageous method for the determination of titanium using graphite furnace atomic absorption spectrometry with slurry sampling has been developed. Titanium is one of the refractory elements that form thermally stable carbides in the graphite tube, which leads to severe memory effects. Trifluoromethane (Freon-23) was applied in the purge gas during the atomization step or alternatively just prior to the atomization to successfully eliminate the problems of carbide formation and increase the lifetime of the furnace tube which could be used for more than 600 heating cycles. A flow rate of 40 mL min^–1 (5% of Freon in argon) was used to obtain symmetrical peaks with no tailing. However, when the gas flow rate was too high (250 mL min^–1) the peak-tailing and memory effects reappeared. Ti was determined in various materials covering a wide range of concentrations, from 2.8 g g^–1 to 12% (m/m) Ti. The accuracy of the method was confirmed by analyzing certified reference materials (CRMs) or by comparing the results with those obtained using inductively coupled plasma–atomic emission spectrometry (ICP–AES) after decomposition of the samples. The materials analyzed were soil, plant, human hair, coal, urban particulate matters, toothpaste, and powdered paint.     

Influence of Earthworms on the Sulfur Turnover in the Soil

Abstract

The effects of earthworm activity on the concentration and isotopic composition of total sulfur in soils was investigated using batch experiments. Two ecologically different lumbricid species, the anecic Lumbricus terrestris and the endogeic Aporrectodea caliginosa, were used. The earthworms were fed birch leaves, beech leaves, cattle manure or mixed plant litter. All food sources differed isotopically (δ³⁴S) from the soil (Parabraunerde). As a reference, one experiment was carried out without additional food.

The experimental results show, that both earthworm species influence the total S-content and the δ³⁴S-values in the soil by digestion of the different food sources. The differences in the total S-content of the earthworm tissues and in the S-isotopic composition of the casts can be attributed to the ecological differences between the earthworm species.     

Monitoring the Transition from Spherical to Polymer‐like Surfactant Micelles Using Small‐Angle X‐Ray Scattering

Despite over a century of modern surfactant science, the kinetic pathways of morphological transitions in micellar systems are still not well understood. This is mainly as a result of the lack of sufficiently fast methods that can capture the structural changes of such transitions. Herein, a simple surfactant system consisting of sodium dodecyl sulfate (SDS) in aqueous NaCl solutions is investigated. Combining synchrotron radiation small‐angle X‐ray scattering (SAXS) with fast stopped‐flow mixing schemes allows monitoring the process where polymer‐like micelles are formed from globular micelles when the salt concentration is suddenly increased. The results show that “worm‐like” micelles are formed by fusion of globular micelles and short cylinders in a fashion that bears similarities to a step‐like polymerization process.     

Dislocation content of geometrically necessary boundaries aligned with slip planes in rolled aluminium

Previous studies have revealed that dislocation structures in metals with medium-to-high stacking fault energy, depend on the grain orientation and therefore on the slip systems. In the present work, the dislocations in eight slip-plane-aligned geometrically necessary boundaries (GNBs) in three grains of near 45° ND rotated cube orientation in lightly rolled pure aluminium are characterized in great detail using transmission electron microscopy. Dislocations with all six Burgers vectors of the ½?1?1?0? type expected for fcc crystals were observed but dislocations from the four slip systems expected active dominate. The dislocations predicted inactive are primarily attributed to dislocation reactions in the boundary. Two main types of dislocation networks in the boundaries were identified: (1) a hexagonal network of the three dislocations in the slip plane with which the boundary was aligned; two of these come from the active slip systems, the third is attributed to dislocation reactions (2) a network of three dislocations from both of the active slip planes; two of these react to form Lomer locks. The results indicate a systematic boundary formation process for the GNBs. Redundant dislocations are not observed in significant densities.     

Determination of Cu and Ni in plants by microdialysis sampling: Comparison of dialyzable metal fractions with total metal content

Microdialysis sampling is presented as an in situ sampling and sample clean-up technique with the potential to be used for determination of metals in plant suspension. Suspensions prepared from ultra pure water and flowers of a Blepharis aspera plant species obtained from a Cu and Ni mineralized site were sampled for Cu and Ni by microdialysis sampling after incorporating an optimal 0.05% (w/v) composition of humic acid in the perfusion liquid. Acid digestion of the plant samples was employed for quantification of Cu and Ni by flame atomic absorption spectrometry. All microdialysis sampling experiments were carried out at room temperature under quiescent conditions using a concentric type of microdialysis probe and electrothermal atomic absorption spectrometry was employed for metal quantification. The versatility of microdialysis as an in situ sampling and sample clean-up technique was demonstrated by the ability to sample Cu and Ni from the complex matrices of plant suspensions. Linear relations between the concentrations of Cu and Ni determined after microdialysis sampling and acid digestion were established and the constant concentration ratios of the metals were found to be 0.0138 and 0.0440 respectively for Cu and Ni thus demonstrating the potential that microdialysis sampling has in prediction of metal concentrations in plant suspension after direct relation with the acid digestion method.     

Determination of Al, Cu, Li and Mn in spruce seeds and plant reference materials by slurry sampling graphite furnace atomic absorption spectrometry

An ultrasonic slurry sampling graphite furnace AAS method was developed for the determination of Al, Cu, Li and Mn in spruce seeds, NBS SRM 1575 pine needles and GBW CRM 07602 bush branches and leaves. The only sample preparation was grinding in a Mixer Mill before preparing a slurry by adding 0.14 mol/L nitric acid to a small sample aliquot. Cryogenic grinding was used for the spruce seeds to solve the problem of agglomerating during grinding at room temperature. A modified sample tray was applied allowing the use of both the commercial 1.5 mL vials and home-made 15 mL vials. With optimal conditions for ultrasonic agitation the homogeneity and particle size distributions in the slurries prepared in the two different vials were similar. Several aspects of the slurry sampling approach are discussed and data of important parameters are given, including the total number of particles injected into the graphite furnace, densities of the materials and percentage of analyte extracted into the liquid phase of the slurry. The density of the materials was determined by two methods; by using a Coulter particle analyser and by using a gravimetric method. The two methods gave similar accuracy and precision. The concentration ranges of the elements (in microg g(-1)) were: 80-2100 for Al, 3-15 for Cu, 0.06-2.5 for Li and 50-700 for Mn. External calibration with aqueous standards was employed. Chemical modifiers were not found to be necessary. The relative standard deviations were in the range 1.7-7%. Analyses of the two certified plant reference materials confirmed the accuracy of the method. In addition no significant difference was found for analyses of digested and slurried spruce seeds. The detection limit was 10 ng g(-1) for Li and 170 ng g(-1) for Cu. The characteristic mass (area measurements) was 4.4 pg for Li and 11 pg for Cu. For Al and Mn less sensitive wavelengths were used.     

Direct Analysis of Beer by ICP-AES: A Very Simple Method for the Determination of Cu, Mn and Fe

A very simple method for determination of trace amount of Cu, Mn and Fe in beer by inductively coupled plasma spectrometry (ICP-AES) was developed. The beer was directly introduced into the plasma, without dilution or adding of reagents, via a conventional V-groove nebulizer. The only sample preparation used was degassing of the beer to remove CO₂. By optimizing the ICP-AES parameters (RF power and Nebulizer gas flow rate) and by the appropriate choice of wavelengths for measurements, sufficient accuracy for the determination of the trace metals was obtained. Various types of beers were analysed by the direct ICP-AES method and for comparison, also with two other methods: by GFAAS and ICP-AES after decomposition. No significant difference was found for Cu and Mn (ANOVA, 95% confidence level) using the three methods. This was normally also the case for Fe; only in one case did the result of Fe by the direct method deviate from the other methods (10% lower results). The limit of detection for the direct method was estimated to 1.1, 0.3, and 1.1 ng mL⁻¹ for Cu, Mn, and Fe, respectively.     

Comparison of single-phase and two-phase measurements in extraction,separation and back-extraction of Cd,Zn and Co from a multi-element matrix using Aliquat 336

Journal of Radioanalytical and Nuclear Chemistry - Cd and Zn were separated from Co, from chloride solutions containing 16 different metal ions. The separation method used was liquid–liquid...