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Analytical and Bioanalytical Chemistry (v.368, #2-3)
Experimental setup for the determination of analytes contained in ultrasonically levitated drops by O. Rohling; C. Weitkamp; B. Neidhart (pp. 125-129).
An automated technique for the determination of analytes in an ultrasonically levitated sample of 2 to 5 μL volume has been developed. Contactless dosing of reagents or solvents into an ultrasonically levitated drop was realized via piezoelectric micropumps. Drop size was continually controlled with a programmed CCD camera. A diode array spectrometer designed for the use with optical fibers was used for absorption and fluorescence measurements. Determinations via direct absorption measurements following the method of standard addition and acid-base titrations with an absorption indicator and a fluorescent indicator were carried out. The mean consumption of sodium hydroxide added via a piezoelectric micropump in five successive titrations with 18 nmol of sulfuric acid inside a levitated drop (indicator bromothymol blue) had a relative standard deviation of 0.7 % and differed only by 0.2 % from the expected value.
Non-invasive identification of chemical compounds by energy dispersive X-ray fluorescence spectrometry, combined with chemometric methods of data evaluation by A. Henrich; P. Hoffmann; H. M. Ortner; T. Greve; H. Itzel (pp. 130-138).
Chemicals from customers’ returns have to be analyzed before they can be reused as raw materials in production. A procedure for non-invasive qualitative analysis of compounds in a closed container based on energy dispersive X-ray fluorescence (EDXRF) spectrometry is described. EDXRF was chosen as method for non-invasive analysis of chemicals through PE bottle walls without opening the bottle. This analysis aims for a quick proof of correspondence between the declaration of a reagent on the label of the bottle and its content. This analytical result cannot be achieved by a mere evaluation of characteristic element lines in EDXRF-spectra in combination with the method of matrix correction or the method of mean atomic number. These methods take into account only a small part of the total information available in an X-ray spectrum. It is shown here that valuable additional information is extractable from the spectral ranges of the Compton-scattering and Rayleigh-scattering areas by the use of methods of multivariate data analysis, especially by principle component analysis (PCA). Regularized discriminant analysis (RDA) was employed to establish a classification scheme for unknown samples.
Kinetics and stoichiometry in the Karl Fischer solution by S. Grünke; G. Wünsch (pp. 139-147).
The mechanisms of the Karl Fischer (K.F.) reaction are reviewed and further investigated. Both kinetic measurements of the iodine concentration and chromatographic determinations of the reaction products were performed. In alcoholic solutions mainly alkyl sulfite is oxidized, and a reaction via partial formation of sulfur trioxide is proposed. In methanol an exact 1:1 stoichiometry (H2O:I2) has been verified. In the aprotic, dipolar solvents acetonitrile, DMF and propylene carbonate HSO3 –is oxidized by iodine. Based on formation and subsequent hydrolysis of base – SO3 adducts the stoichiometric factor for water is determined by type and concentration of the base, by the concentration of water and by the solvent itself. – In K.F. reagents the oxidation of SO2 by aerial oxygen to sulfate and alkyl sulfate takes place as a side reaction.
Comparative performance study of ICP mass spectrometers by means of U “isotopic measurements” by C. R. Quétel; J. Vogl; T. Prohaska; S. Nelms; P. D. P. Taylor; P. De Bièvre (pp. 148-155).
The performance of four commercially available ICPMS instruments of three different types was compared by means of uranium “isotopic measurements”. Examined were two quadrupole sector (different generation, different manufacturer), one single detector double focusing magnetic sector and one multiple collector double focusing magnetic sector instruments. The same samples of the IRMM-072 series were used under routine conditions to measure the 233U/235U and the 233U/238U ratios which, in these samples, vary over almost three orders of magnitude from ∼ 1 to ∼ 2 · 10–3. Within expanded (k = 2) uncertainties, good agreement was observed between the certified values and the data internally corrected for mass-discrimination effects. The magnitude of the evaluated uncertainties was different for each type of instrument. With the multiple collector instrument, expanded uncertainties varied from ± 0.04% to± 0.24% for the 233U/235U ratio, and from ± 0.08% to ± 0.27% for the 233U/238U ratio. They were ∼ 1 to 5 times larger with the single detector magnetic sector instrument, and ∼ 10 to 25 times larger with both quadrupole sector instruments. With the multiple collector instrument, repeatability of the measurements seemed to be limited by the difficulty of correcting properly for instrumental background, whereas with the single detector magnetic sector instrument the counting statistics was the only limitation (on smallest ratios). Apparent mass-discrimination was clearly found to be larger but more reproducible (and hence easier to correct for) in the case of magnetic sector instruments than for both quadrupole sector instruments. If space charge effects were the main source of mass-discrimination for all instruments, these results are in contradiction with the hypothesis of the size of mass-discrimination decreasing with the acceleration voltage. With the single detector magnetic sector instrument in particular (when operated by changing the ion energy only), our results pointed at more than only one major source of mass-discrimination, with variable size depending on the ratios measured.
Noise power spectra and recovery rates obtained with different nebulizer systems in ICP atomic emission spectrometric analyses in the case of different types of salts and salt contents by Rainer Nehm; José A. C. Broekaert (pp. 156-161).
The features of different nebulizer systems (cross-flow-, Meinhard- and GMK-system) in the ICP atomic emission spectrometric analyses of solutions with different contents of different salts were evaluated. As basis for the comparison of the nebulizer systems the recovery rates and noise power spectra were used. Both showed that the GMK-system could be used for the widest diversity of salts (sodium chloride, ammonium sulfate and sodium tetraborate) and concentration range (0–10% (m/v)) followed by the cross-flow-system and the Meinhard-system in ICP-OES using a 1 kW argon ICP. Of all nebulizer systems the nebulizer according to Meinhard has the lowest performance for the salts investigated. The noise power spectra of all nebulizer systems are dominated by interference noise from the sample introduction system. This noise increases with the salt concentration of the solution and the GMK-system shows the lowest increase, followed by the cross-flow- and Meinhard-system.
Determination of arsenic by inductively coupled plasma mass spectrometry – comparison of sample introduction techniques by Hilde Uggerud; W. Lund (pp. 162-165).
A comparison is made of four sample introduction techniques for the determination of As by inductively coupled plasma mass spectrometry. The techniques studied were 1) flow injection with pneumatic nebulization (FIA-PN), 2) direct electrothermal vaporization (ETV), 3) continuous hydride generation (HG) and 4) hydride generation with in situ trapping followed by electrothermal vaporization (HG-ETV). It was found that FIA-PN and ETV gave similar detection limits in concentration units (about 20 pg mL–1), although ETV had a much lower absolute detection limit (0.2 pg). Sample introduction by hydride generation gave an inferior detection limit (100–200 pg mL–1), also in combination with in situ trapping and ETV, owing to the blank signal from traces of As in NaBH4 which is difficult to eliminate. The results indicate that the more elaborate sample introduction techniques based on ETV and HG may not offer significant advantages compared to normal solution nebulization for the determination of As in simple sample matrices such as natural fresh waters, where matrix removal is not required.
Improvement of the model for calculation of relative sensitivity coefficients in inductively coupled plasma mass spectrometry by G. I. Ramendik; E. V. Fatjushina; A. I. Stepanov; V. S. Sevastyanov (pp. 166-172).
Relative sensitivity coefficients (RSCs) were determined for 68 elements in inductively coupled plasma mass spectrometry (ICP-MS). It was shown that the Saha equation gives a rough description of ionization processes in ICP. A dependence of RSCs on the absolute electronegativity of atoms was found. This parameter is substantially affecting the accuracy of RSCs calculation for chemically active elements. Taking into account absolute electronegativities of the atoms for the calculation of RSCs, the ion formation processes in ICP-MS could be better described than by using first ionization potentials. The mean relative systematic error of RSCs calculation using absolute electronegativity was improved to 0.30.
A new strategy of solution calibration in laser ablation inductively coupled plasma mass spectrometry for multielement trace analysis of geological samples by Carola Pickhardt; J. S. Becker; Hans-Joachim Dietze (pp. 173-181).
Because multielement trace analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is often limited by the lack of suitable reference materials with a similar matrix composition, a novel quantification strategy using solution calibration was developed. For mass spectrometric multielement determination in geological samples a quadrupole-based LA-ICP-MS is coupled with an ultrasonic nebulizer (USN). In order to arrange matrix matching the standard solutions are nebulized with a USN during solution calibration and simultaneously a blank target (e.g. lithium borate) is ablated with a focused laser beam. The homogeneous geological samples were measured using the same experimental arrangement where a 2% nitric acid is simultaneously nebulized with the USN. Homogeneous targets were prepared from inhomogeneous geological samples by powdering, homogenizing and fusing with a lithium borate mixture in a muffle furnace at 1050 °C. Furthermore, a homogeneous geological glass was also investigated. The quantification of analytical results was performed by external calibration using calibration curves measured on standard solutions. In order to compare two different approaches for the quantification of analytical results in LA-ICP-MS, measured concentrations in homogeneous geological targets were also corrected with relative sensitivity coefficients (RSCs) determined using one standard solution only. The analytical results of LA-ICP-MS on various geological samples are in good agreement with the reference values and the results of other trace analytical methods. The relative standard deviation (RSD) for trace element determination (N = 6) is between 2 and 10%.
Detection of heavy metals in water by fluorescence spectroscopy: On the way to a suitable sensor system by H. Prestel; A. Gahr; R. Niessner (pp. 182-191).
In order to develop a fiber optical heavy metal ion detection system, the applicability of selected complexing agents with fluorescent properties has been studied. Beginning with the application of known chelators, like BTC-5N, Newport Green™, neocuproine, and chromotropic acid, a sensor configuration has been found, which allows the detection of Cd2+, Ni2+, and Cu2+ well below the chemical parameter threshold values of the new Water Quality Directive 98/83/EU. The sensor itself uses a membrane separation of the chelator flow from the sample volume. The diffusion across the membrane limits the response time to about 15 to 20 min. Applications are seen in monitoring networks.
Dyeless optical detection of ammonia in the gaseous phase using a pH-responsive polymer – characterization of the sorption process by F. Rathgeb; D. Reichl; M. Herold; O. Mader; T. Mutschler; G. Gauglitz (pp. 192-195).
pH-responsive polymers enable the dyeless optical detection of acidic or basic pollutants in air. The characterization of the sorption process and the optimization of the response time of the sensitive layers were highlighted. The swelling of a pH-responsive polysiloxane induced by sorption of gaseous ammonia was investigated by measurement techniques such as spectroscopic ellipsometry (SE) and infrared spectroscopy (IR). Furthermore, the pH-responsive polymer was applied for the detection of gaseous ammonia using the LED-based reflectometric interference spectroscopy set-up (RIfS4λ). A limit of detection of 0.30 mg/m3 ammonia and a response time (t90%) of 35 s could be verified. The application of pH-responsive polymers can be a powerful alternative to dye-based optical sensing, since photobleaching or leaching of the sensitive functional unit cannot occur applying this approach, and since the properties of the sensitive layer proved to be very promising.
Optical sensor for seawater salinity by Christian Huber; I. Klimant; Christian Krause; Tobias Werner; Torsten Mayr; Otto S. Wolfbeis (pp. 196-202).
An optical sensor for the measurement of salinity in seawater has been developed. It is based on a chloride-quenchable fluorescent probe (lucigenin) immobilized on a Nafion film. Two approaches for measuring salinity via chloride concentration are presented. In the first, a change in salinity corresponds to a change in the fluorescence intensity of lucigenin. In the second, the fluorescence intensity information is converted into a phase angle information by adding an inert phosphorescent reference luminophore (a ruthenium complex entrapped in poly(acrylonitrile) beads). Under these conditions, the chloride-dependent fluorescence intensity of lucigenin can be converted into a chloride-dependent fluorescence phase shift which serves as the analytical information. This scheme is referred to as dual lifetime referencing (DLR). The sensor was used to determine the salinity in seawater and brackish water of the North Sea.
Novel teststrip with increased accuracy by H. Starp; N. Buschmann; K. Cammann (pp. 203-207).
A new type of a simple and cheap teststrip for liquid samples is described. It is based on microchromatography or microtitration on a porous, capillary-active substrate (e.g., filter paper or a similar absorbent material). In case of microchromatography an analyte-selective indicator (and other auxiliary reagents) is impregnated or immobilized on the capillary-active substrate; in case of micro-titration the capillary-active substrate contains a titrant which reacts stoichiometrically with the analyte. Quantitative analysis is performed by measurement of an area (which had changed its color) rather than by evaluation of the shade or intensity of a color (like in conventional teststrips). In order to show the broad applicability of this new principle teststrips for different analytes like Quaternary Ammonium Compounds (QACs), the cation Ni2+, the anion SO4 2– and H2O2 are described. The detection limit and working range of the novel teststrip can be adjusted by variation of its size.
Sulfur speciation by capillary zone electrophoresis: conditions for sulfite stabilization and determination in the presence of sulfate, thiosulfate and peroxodisulfate by Leandro M. de Carvalho; G. Schwedt (pp. 208-213).
Capillary zone electrophoresis (CZE) was used for the separation of the sulfur species SO3 2–, SO4 2–, S2O3 2– and S2O8 2–. Using an electrolyte system with 9.5 mmol L–1 potassium chromate as UV-absorbing probe and 1 mmol L–1 diethylenetriamine (DETA) as electroosmotic flow modifier, various possibilities for the stabilization of sulfite and electrophoretic separation of the sulfur anions were investigated. By adding 5% propanol as a stabilizer to both the working electrolyte and the sample solution, a good stabilization for sulfite and a separation of the sulfur anions in a short analysis time (4 min) was achieved. The advantages by using propanol instead of other stabilizers often used in analytical techniques are discussed. The electrophoretic separation of the sulfur anions was optimized with respect to the pH of the working electrolyte and concentration of the electroosmotic flow modifier (DETA). The detection limits achieved for SO3 2–, SO4 2–, S2O3 2– and S2O8 2– were 0.35, 0.25, 0.78 and 0.80 mg L–1, respectively.
Stability studies of arsenic, selenium, antimony and tellurium species in water, urine, fish and soil extracts using HPLC/ICP-MS by Torsten Lindemann; A. Prange; Walter Dannecker; Bernd Neidhart (pp. 214-220).
The stability of arsenic, selenium, antimony and tellurium species in water and urine (NIST SRM 2670n) as well as in extracts of fish and soil certified reference materials (DORM-2 and NIST SRM 2710) has been investigated. Stability studies were carried out with As(III), As(V), arsenobetaine, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), phenylarsonic acid (PAA), Se(IV), Se(VI), selenomethionine, Sb(III), Sb(V) and Te(VI). Speciation analysis was performed by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Best storage of aqueous mixtures of the examined species was achieved at 3 °C whereas at –20 °C species transformation especially of selenomethionine and Sb(V) took place and a new selenium species appeared within a period of 30 days. Losses and species transformations during extraction processes were investigated. Extraction of the spiked fish material with methanol/water led to partial conversion of Sb(III), Sb(V) and selenomethionine to two new antimony and one new selenium species. The other arsenic, selenium and tellurium species were almost quantitatively extracted. For soil spiked with MMA, PAA, Se(IV) and Sb(III), recoveries after extraction with water and sulfuric acid (0.01 mol/L) were below 20%.
Depth profile analysis of various titanium based coatings on steel and tungsten carbide using laser ablation inductively coupled plasma –“time of flight” mass spectrometry by Davide Bleiner; Alexei Plotnikov; Carla Vogt; Klaus Wetzig; D. Günther (pp. 221-226).
A homogenized 193 nm ArF* laser ablation system coupled to an inductively coupled plasma-”Time of Flight”-mass spectrometer (LA-ICP-TOFMS) was tested for depth profiling analysis on different single-layer Ti based coatings on steel and W carbides. Laser parameters, such as repetition rate, pulse energy and spatial resolution were tested to allow optimum depth related calibration curves. The ablation process using a laser repetition rate of 3 Hz, 120 μm crater diameter, and 100 mJ output energy, leads to linear calibration curves independent of the drill time or peak area used for calibrating the thickness of the layer. The best depth resolution obtained (without beam splitter) was 0.20 μm per laser shot. The time resolution of the ICP-TOFMS of 102 ms integration time per isotope was sufficient for the determination of the drill time of the laser through the coatings into the matrix with better than 2.6% RSD (about 7 μm coating thickness, n = 7). Variation of the volume of the ablation cell was not influencing the depth resolution, which suggests that the depth resolution is governed by the ablation process. However, the application on the Ti(N,C) based single layer shows the potential of LA-ICP-TOFMS as a complementary technique for fast depth determinations on various coatings in the low to medium μm region.
Direct solid sampling electrothermal atomic absorption spectrometry for the analysis of high-purity niobium pentaoxide by M. D. Huang; V. Krivan (pp. 227-234).
A direct solid sampling electrothermal atomic absorption spectrometry (SoS-ETAAS) method for ultratrace analysis of powdered niobium pentaoxide for Al, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn has been developed. The elements K, Mg, Na and Zn could be determined without any chemical modification. However, in the determination of the elements Al, Co, Cr, Cu, Fe, Mn and Ni, serious matrix-caused non-spectral interferences and background occurred which made their determination impossible. This problem was remedied by conversion of the niobium pentaoxide matrix into the thermally stable niobium carbide by using methane atmosphere during the pyrolysis stage. The development resulted in establishing an extraordinary powerful method for the analysis of niobium pentaoxide in term of limits of detection, accuracy, simplicity and analysis time. Quantification was performed using calibration curves measured with aqueous standard solutions. The accuracy was checked by comparing the results with those obtained by ETAAS in analysis of slurries and digests of the sample. Due to almost complete freedom of blank and high applicable sample amounts (up to 15 mg), extremely low limits of detection (0.5–2 ng/g) were achieved.
Determination of metal additives and bromine in recycled thermoplasts from electronic waste by TXRF analysis by H. Fink; U. Panne; M. Theisen; R. Niessner; T. Probst; X. Lin (pp. 235-239).
A new method for analysis of metal additives in recycled thermoplasts from electronic waste was developed, based on dissolving the samples in an organic solvent and subsequent analysis of the corresponding solutions or suspensions by total-reflection X-ray fluorescence spectroscopy (TXRF). The procedure proved to be considerably less time consuming than the conventional digestion of the polymer matrix. Additives containing Ti, Zn, Br, Cd, Sn, Sb, and Pb were analyzed in a hundred randomly selected samples from recycling, which provided an overview of the range of elemental concentrations in thermoplasts utilized for consumer electronics. The results were validated independently by instrumental neutron activation analysis (INAA), subsequent regression analysis confirmed the trueness of the chosen approach.
Determination of palladium in gasoline by neutron activation analysis and automated column extraction by Michael Schwarzer; M. Schuster; Roger von Hentig (pp. 240-243).
Palladium in gasoline was determined by means of neutron activation analysis (NAA) and selective sorbent extraction. Unleaded gasoline consistent with DIN EN 228, RON 95 was irradiated at a thermal neutron flux of Φth = 1.68 · 1013s–1cm–2 and an epithermal neutron flux of 3.32 · 1011s–1cm–2 for tirr = 12 h. The irradiated gasoline was digested with nitric acid and palladium was then separated as N,N-diethyl-N’-benzoylthiourea complex by an automated column pre-concentration procedure. The eluate of 50 μL was dried on a filter paper and the 88.03 keV photons resulting from the decay of 109Pd were detected in a low level HPGe spectrometer with an efficiency of 35.5%. Severe interferences with other matrix constituents, especially 82Br could be overcome and the detection limit for palladium was improved to 3.4 ng/L at a confidence level of 90%. Although the analytical procedure applied yielded the lowest detection limit for palladium obtained in gasoline up to now, no indications for the presence of palladium were found.
Multifunctional organic nitrates as constituents in European and US urban photo-smog by J. Kastler; W. Jarman; K. Ballschmiter (pp. 244-249).
Air samples of the atmospheric ground layer in the cities of Ulm in Germany, Las Vegas, Nevada, and Salt Lake City, Utah, in the US were analyzed for organic nitrates. The air samples were taken around noon in summer at sunny weather conditions. 43 (C6–C13) alkyl mononitrates, 24 (C3–C6) alkyl dinitrates, and 19 (C2–C6) hydroxy alkyl nitrates have been identified. The analytical protocol included high-volume-sampling, NP-HPLC group separation, high resolution capillary gas chromatography, and detection by the highly selective mass spectrometer detector (SIM mode, m/z = 46). The levels of the sum of 15 (C6–C10) alkyl mononitrates ranged from 2.9 to 11.0 parts per trillion (ppt(v)). The levels of the sum of 21 (C3–C6) alkyl dinitrates ranged from 2.3 to 10.5 ppt(v), and the levels of the sum of 7 (C2–C4) hydroxy alkyl nitrates ranged from 7.3 to 28 ppt(v), respectively, in the urban air samples. These results emphazise the contribution of the alkyl dinitrates and hydroxy alkyl nitrates besides the alkyl mononitrates to the budget of NOY compounds. No major differences in levels and pattern of the organic nitrates are present in air of the German and the US cities.
Copper-complexation index as a polarographic summation parameter for the determination of chelating agents in water by Steffen Esser; B. W. Wenclawiak; Heinrich Gabelmann (pp. 250-255).
Polarography of the copper(II)-complexes of chelating agents is shown to be a suitable basis for a summation parameter for the total concentration of these chemicals in water (expressed as the copper-complexation index). Using 12 chelating agents (ATMP, BAED, CDTA, DTPA, DTPMP, EDTA, EDTMP, EDTP, EGTA, HEDP, NTA, PBTC) all listed in DIN 38409-H26 and DIN 38413-P5 a satisfactory reproducibility of the method used was obtained. In addition several commercial tensides, detergents in washing and deliming products were investigated.
Simultaneous multi-element analysis of trace elements in soil samples by means of high-resolution inductively coupled plasma sector field mass spectrometry (SF-ICP-MS) by C. Latkoczy; Thomas Prohaska; Gerhard Stingeder; Walter W. Wenzel (pp. 256-262).
The potential of SF-ICP-MS for trace element analysis in complex environmental matrices such as soil solutions was investigated. Spectral interferences found in mass spectra of soil matrices are presented in detail. Furthermore, the influences of single components of the soil matrix on the signal intensity of selected elements were studied. Detection limits of different elements are presented with respect to the composition of the matrix. A fast and accurate method for quasi-simultaneous determination of Al, Si, P, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Hg and Pb in aqueous soil extracts was established.
Metal(loid)organic compounds in contaminated soil by A. V. Hirner; U. M. Grüter; J. Kresimon (pp. 263-267).
13 samples of soils contaminated with petrol, coaly residues, shredder and domestic waste have been investigated by low temperature gas chromatography with plasma mass spectrometry detection after sample derivatisation by hydride generation (HG/LT-GC/ICP-MS). 24 organic compounds of 9 elements could be analysed, one fifth of them exceeding the concentration of 1 μg/kg. These results are roughly comparable with those on harbour and river sediments, and are discussed in respect to a preliminary evaluation of the emission potential of solid waste and contaminated soil as well as waste treatment processes.
Retention behavior of humic substances in reversed phase HPLC by G. Preuße; S. Friedrich; R. Salzer (pp. 268-273).
Recovery as well as appearance and abundance (in percent) of different fractions of humic substances are found to depend on injected sample amounts in reversed phase HPLC. Sample amounts have been varied both by varying sample concentration and sample volume. In case of lowest amounts injected only two fractions were obtained for a commercial humic acid sodium salt, i.e. one for excluded molecules and one for hydrophobic components. The abundance of excluded molecules decreases upon increasing amounts injected. Another three fractions are obtained upon increasing amount injected: a hydrophilic fraction and two hydrophobic ones. This behavior is explained by auxiliary equilibria between excluded components and humic molecules previously adsorbed on the stationary phase.
Structural and elemental investigations of isolated aquatic humic substances using X-ray photoelectron spectroscopy by H. Bubert; J. Lambert; P. Burba (pp. 274-280).
Structural and elemental investigations of aquatic humic substances (HS) by means of X-ray photoelectron spectroscopy (XPS) are described. For that purpose small amounts (10–50 μg) of dissolved reference HS, which were characterized within the German research program DFG-ROSIG, were dried as thin films on small pieces of a high-purity silicon wafer. The photoelectrons from such HS layers exhibited characteristic signals of carbon C1s, nitrogen N1s, oxygen O1s and sulfur S2s, which could be fitted by Gaussian curves and used for the quantification of various moieties of HS: carbon (C-C, C-O, C=O, O=C-O), oxygen (C-O, C=O), nitrogen (C-N, C-N+) and sulfur. Moreover, by adding up the element signals of the HS samples their elemental composition of C, O, N and S was assessed. A comparison of the data based on solution state NMR and conventional elementary analysis revealed a satisfactory accuracy with those obtained by XPS.
Characterization of high molecular weight cadmium species in contaminated vegetable food by K. Günther; G. Ji; B. Kastenholz (pp. 281-287).
Spinach and radish grown from seeds were each contaminated with 4 different amounts of cadmium. After a cell breakdown of the eatable parts and centrifugation of the resulting homogenates all supernatants (cytosols) were separated by gel permeation chromatography (GPC). The size-range of the GPC method used was about 20–8000 kDa for globular proteins. The high molecular weight (HMW-Cd-SP, 150–700 kDa) and the low molecular weight Cd species (LMW-Cd-SP, < 150 kDa) in all plant cytosols eluted at about the same retention volume by GPC. The most important Cd binding form in the cytosols of all plants was found to be HMW-Cd-SP. The Cd elution maxima were detected in the range of about 200 kDa. The Cd determinations were performed with ET-AAS by means of matrix modifier. By incubating chosen cytosols with a proteinase before the GPC it was verified that the HMW-Cd-SP in both vegetables are Cd proteins. The molar proportions protein/Cd were about 2–6 in the respective GPC fractions of the HMW-Cd-SP of the highest contaminated plants. The GPC fractions of the HMW-Cd-SP of spinach and radish were further separated by a preparative, native and continuous polyacrylamide gel electrophoresis (PAGE) method. At pH 8 the species were negatively charged, had only a small UV-absorption at 280 nm and showed a very similar elution behavior in all analyzed cytosols. Therefore, we suppose that the HMW-Cd-SP of these two different vegetable foodstuffs have a very similar chemical structure.
Electrothermal atomic absorption spectrometric determination of cobalt in biological samples and natural waters using a flow injection system with on-line preconcentration by ion-pair adsorption in a knotted reactor by Karima Benkhedda; Heidi Goenaga Infante; E. Ivanova; F. Adams (pp. 288-292).
An on-line flow injection preconcentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a preconcentration time of 60 s and a sample loading flow rate of 5 mL min–1. The detection limit (3σ) is 5 ng L–1. The relative standard deviation at the 0.2 μg L–1 level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.
Study of the binding of 114mIn radiotracer to human serum components by ultrafiltration and chromatography by M. Van Hulle; K. De Cremer; R. Cornelis (pp. 293-296).
The chemical speciation of indium in serum was studied. Ultrafiltration was used to investigate the influence of several buffer systems on the binding characteristics of indium in serum and to study the association of indium with transferrin and albumin. This was performed by means of batch incubation experiments with a 114mIn tracer. Different buffer systems were investigated. A series of bicarbonate, Tris:HCl and HEPES buffers were found to fit for this purpose. Phosphate buffer was not suitable, as it is capable of disrupting the binding between indium and transferrin. Batch ultrafiltration experiments with 114mIn incubated solutions of transferrin and albumin showed that both proteins are capable of binding indium to a high degree. Three chromatographic techniques (SEC, AEC, AC) were used to study the different chemically active species of indium in serum. It is concluded that next to transferrin, albumin is also responsible for the binding and transport of indium in serum.
Low-molecular-weight organoiodine and organobromine compounds released by polar macroalgae – The influence of abiotic factors by F. Laturnus; B. Giese; Christian Wiencke; Freddy C. Adams (pp. 297-302).
The influence of temperature, light, salinity and nutrient availability on the release of volatile halogenated hydrocarbons was investigated in the Antarctic red macroalgal species Gymnogongrus antarcticus Skottsberg. Compared to standard culture condition, an increase in the release rates of iodocompounds was generally found for the exposure of the alga to altered environmental conditions. Macroalgae exhibited higher release rates after adaptation for two months to the changed factors, than after short-term exposure. Monitoring the release rates during a 24 h incubation period (8.25 h light, 15.75 h darkness) showed that changes between light and dark periods had no influence on the release of volatile halocarbons. Compounds like bromoform and 1-iodobutane exhibited constant release rates during the 24 h period. The formation mechanisms and biological role of volatile organohalogens are discussed. Although marine macroalgae are not considered to be the major source of biogenically-produced volatile organohalogens, they contribute significantly to the bromine and iodine cycles in the environment. Under possible environmental changes like global warming and uncontrolled entrophication of the oceans their significance may be increase.
Stable isotope dilution analyses of molybdenum in meteorites by M. E. Wieser; J. R. De Laeter (pp. 303-306).
Isotope dilution mass spectrometry is an ideal analytical technique to measure the elemental abundance of Mo in C1 carbonaceous chondrites and the metallic and troilite phases of iron meteorites. The mean abundance of Mo in two C1 meteorites is 0.909 ± 0.040 μg/g which corresponds to a value of 2.55 atoms Mo with respect to Si equal to 106 atoms, which is identical to the currently accepted solar system abundance. The partitioning of Mo between the metallic and sulfide phases in the Mundrabilla iron meteorite was found to be 6.0 ± 0.2 μg/g and 8.6 ± 0.3 μg/g, respectively. A new, precise Mo concentration of 1.54 ± 0.04 μg/g for the Geochemical Reference Standard BCR-1 is also reported.