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Analytical and Bioanalytical Chemistry (v.361, #2)
Definitive method certification of clinical analytes in lyophilized human serum: NIST Standard Reference Material (SRM) 909b by C. S. Phinney; K. E. Murphy; M. J. Welch; P. M. Ellerbe; S. E. Long; K. W. Pratt; S. B. Schiller; L. T. Sniegoski; M. S. Rearick; T. W. Vetter; R. D. Vocke (pp. 71-80).
The National Institute of Standards and Technology (NIST) has developed several Standard Reference Materials (SRMs) based on human serum. NIST SRM 909b, Human Serum, is a lyophilized human serum material with concentrations for seven organic and six inorganic analytes at two levels certified solely by definitive methods (DMs). This material provides the vehicle by which high precision, high accuracy measurements made with DMs at NIST can be transferred through the measurement hierarchy to other laboratories. Isotope dilution gas chromatographic-mass spectrometric (GC-IDMS) methods were applied to measure cholesterol, creatinine, glucose, urea, uric acid, triglycerides, and total glycerides. Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used for determination of lithium, magnesium, potassium, calcium, and chloride. In addition, chloride was determined by coulometry, providing a comparison between two DMs. Sodium, which lacks a stable isotope that would permit isotope dilution mass spectrometric (IDMS) measurement, was determined by gravimetry. SRM 909b includes certified values for total glycerides and triglycerides, which were not certified in the previous lot of this material (SRM 909a). Improvement in uniformity of vial fill weight in the production of SRM 909b resulted in smaller certified uncertainties over previous freeze-dried serum SRMs. Uncertainties at the 99% level of confidence for relative expanded uncertainty (%) for certification of the organic analytes on a mmol/L/g basis ranged from 0.44% for urea (level II) to 5.04% for glucose (level II). (In-house studies have shown glucose to be a relatively unstable analyte in similar lyophilized serum materials, degrading at about 1% per year.) Relative expanded uncertainties (99% C.I.) for certification of inorganic analytes on a mmol/L/g basis ranged from 0.25% for chloride (level I) to 0.49% for magnesium (level II).
Pulsed microchip laser induced fluorescence for in situ tracer experiments by C. Moulin; Xavier Vitart (pp. 81-85).
A compact system for remote and non intrusive in situ analysis of fluorescent tracers using a newly developed pulsed microchip laser coupled to fiber optics was used for in situ rhodamine determinations. By using a crystal doubling in front of the microchip Nd-YAG laser, it is possible to obtain 532 nm at 5 kHz with an energy of 0.6 μJ in a 0.5 ns pulse. Using fiber optics and a passive optode, it was possible to analyze remotely the fluorescence of rhodamine with a compact detection system (monochromator and photomultiplier). Limits of detection down to 10–10–10–11 mol/L can be reached depending on the rhodamine studied. Such a laser can be directly implanted in the optode avoiding laser losses when exciting in the U.V.
Performance comparison between packed column supercritical fluid chromatography (SFC) and HPLC using cyclandelate as the model analyte by I. C. Bhoir; B. Raman; M. Sundaresan; A. M. Bhagwat (pp. 86-89).
A reproducible and fast method has been developed for the assay of cyclandelate in bulk and drug forms using packed column supercritical fluid chromatography using dicyclohexyl phthalate (DCHP) as internal standard. The drug and the internal standard were resolved by elution with supercritical fluid carbon dioxide doped with 14.29% (v/v) methanol on an RP-C18 column and detected spectrophotometrically at 228 nm. Chromatographic figures of merit using C8, C18, cyano and phenyl columns have been assessed. Parallel experiments have been performed by HPLC and the data have been compared. Supercritical fluid extraction using CO2 modified with a small amount of methanol was found to give quantitative analytical recoveries of cyclandelate from a dosage form. SFC has been shown to be a viable, faster alternative technique to HPLC generating less disposable waste.
Closed vessel microwave-assisted wet digestion with simultaneous control of pressure and temperature in all vessels by M. Zischka; Peter Kettisch; Andreas Schalk; Günter Knapp (pp. 90-95).
A novel system for microwave-assisted wet digestion in closed vessels is described. Six pressure vessels made of quartz or Hostaflon® TFM are placed in a special rotor in a microwave oven. During sample decomposition the pressure and temperature are measured in each vessel, and the data are transferred from the rotor by means of infrared light to the control unit. This means that no pneumatic or electronic connections to the vessels need to be established, providing very easy handling. The temperature history of each vessel is recorded; so the progress of each sample digestion may be reconstructed later on. Thus the requirements for quality control in sample digestion are available for the first time. For sample digestion at 75 bar and up to 280° C, quartz vessels with 50 mL volume are used. Depending on the matrix, the maximum sample loading capacity is 1.2 g. TFM-vessels with 100 mL volume work at 30 bar up to 240° C. The performance of the digestion system was tested with twelve standard reference materials. The results closely matched the certified values.
The analysis of antimony species by using ESI-MS and HPLC-ICP-MS by J. Lintschinger; O. Schramel; A. Kettrup (pp. 96-102).
A new method for the separation of organic antimony as trimethylantimony dichloride (TMSbCl2) and inorganic Sb(V) and Sb(III) by using anion exchange high-performance liquid chromatography coupled with inductively-coupled plasma mass spectrometry (ICP-MS) is presented. In comparison with previous work the detection limits for both species were significantly decreased, down to 5 ngL–1, mainly by avoiding any contamination from the chromatographic device. Using an ultrasonic nebulizer (USN) improved the detection limits for inorganic Sb species, but was useless for the HPLC method due to problems in the recovery of the TMSbCl2. Matrix interferences of the chromatographic determination were studied in detail and the method was applied to environmental samples assumed to contain organic antimony species. Additionally, the molecular structure of the TMSbCl2 in solution was studied by using electrospray-ionization mass spectrometry (ESI-MS) showing that this species occurs most probably as [TMSbOH]+ in aqueous solutions.
Highly selective catalytic determination of ultra trace amounts of rhodium by linear sweep voltammetry by A. A. Ensafi; K. Zarei (pp. 103-105).
A highly selective and sensitive method is proposed for the determination of rhodium, based on the catalytic effect on the oxidation of Nile blue by periodate. The reaction rate is monitored by measuring the current of Nile blue at –0.37 V vs. Ag/AgCl reference electrode. The linear working range is 5 to 100 ng/mL with a limit of detection of 0.1 ng/mL. The interference effects of more than forty ions were studied. The method was used for the determination of Rh (III) in synthetic samples with satisfactory results.
Determination of copper, lead, cadmium, zinc, and iron in calcium fluoride and other fluoride-containing samples by means of direct solid sampling GF-AAS by W. Schrön; A. Detcheva; B. Dreßler; K. Danzer (pp. 106-109).
Direct solid sampling graphite furnace AAS (SS-GF-AAS) provides an advantageous alternative to the conventional AAS which requires wet digestion of the samples. This method is suitable for trace element determination in calcium fluoride and other fluoride-containing samples. Matrix effects were studied by using calibration standards, certified reference materials with different matrices and by means of three-dimensional calibration. 3D calibration is suitable for selection of calibration samples for more reliable analyses. Cu, Pb, Cd, Zn, and Fe were determined by means of calibration with variation of sample weight using certified reference materials and suitable fluoride-containing calibration samples.
Correlation between XPS, Raman and TEM measurements and the gas sensitivity of Pt and Pd doped SnO2 based gas sensors by J. Kappler; N. Bârsan; U. Weimar; A. Dièguez; J. L. Alay; A. Romano-Rodriguez; J. R. Morante; W. Göpel (pp. 110-114).
Nanocrystalline thick-film SnO2 sensors with different dopants were fabricated by an optimized screen printing process and subsequent annealing. Powders were used as starting materials which were prepared by a wet chemical process from SnCl4. Microanalysis was performed of both, the precursors and the final sensor materials with their different annealing conditions. Gas sensing tests with CO, CH4 and NO2 in air with controlled humidity were correlated with results from X-ray photoemission spectroscopy (XPS), Raman spectroscopy and transmission electron microscopy (TEM). As an interesting result, the distribution of the transition metal dopants Pd and Pt (as deduced from TEM and XPS data) rules out the existence of metallic clusters or even atoms in the metallic state at the surface. This finding does not allow to explain the sensor effects on SnO2 based materials as usually done by means of spill-over effects or Fermi energy control.
An amperometric biosensor using toluidine blue as an electron transfer mediator intercalated in α-zirconium phosphate-modified horseradish peroxidase immobilization matrix by Feng Yang; Chuanmin Ruan; Jinsuo Xu; Chenghong Lei; Jiaqi Deng (pp. 115-118).
A novel H2O2 biosensor was constructed employing α-zirconium phosphate as a new support substrate to hold an electron shuttle toluidine blue between a glassy carbon electrode and horseradish peroxidase. Toluidine blue was intercalated into α-zirconium phosphate-modified horseradish peroxidase immobilization matrix cross-linked on a glassy carbon electrode surface via bovine serum albumin-glutaraldehyde. This co-immobilization matrix of the mediator and the enzyme was formed from the α-zirconium phosphate (α-ZrP)-toluidine blue (TB) inclusion colloid in which horseradish peroxidase (HRP) was dissolved. Intercalation of TB in layered α-ZrP was investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and electrochemical measurements. TB immobilized in this way underwent a quasi-reversible electrochemical redox reaction at the electrode. Cyclic voltammetry and amperometric measurements demonstrated good stability and efficiently-shuttled electrons between HRP and the electrode. The sensor responded rapidly to H2O2 with a detection limit of 3.0 × 10–7 mol/L.
Spatial distribution profiles of magnesium and strontium in speleothems using laser-induced breakdown spectrometry by José M. Vadillo; I. Vadillo; F. Carrasco; J. J. Laserna (pp. 119-123).
Laser-induced breakdown spectrometry (LIBS) has been applied to spatially locate several atomic species in speleothems taken from the Nerja’s Cave (Málaga, Spain). Spatial distribution profiles of Mg at 285.21 nm and Sr at 407.77 nm were obtained while the laser was rastered through different paths along the sample. These elements were selected due to their importance as palaeoclimatic indicators. The 532 nm output of a Nd:YAG laser was used to irradiate the samples and generate the plasma that was spectrally analyzed and detected by using an intensified CCD detector. The signals were normalized to the Ca line to minimize pulse-to-pulse fluctuations in the laser source. Several studies were carried out to check for the point-to-point heterogeneity of the natural speleothem.
Determination of H2O2 and organic peroxides by high-performance liquid chromatography with post-column UV irradiation, derivatization and fluorescence detection by Jianguo Hong; J. Maguhn; Dieter Freitag; Antonius Kettrup (pp. 124-128).
A method for the determination of hydrogen peroxide and several organic peroxides by high-performance liquid chromatography with post-column UV irradiation, derivatization and fluorescence detection is described. By means of post-column UV irradiation in the presence of water organic peroxides are converted into hydrogen peroxide and organic hydroperoxides, which react rapidly with the post-column derivatization agent p-hydroxyphenylacetic acid (PHPAA) under catalysis of horseradish peroxidase to yield the fluorescent PHPAA dimer that is detected at excitation and emission wavelengths of 285 and 400 nm, respectively. The detection limit for hydrogen peroxide is 14 ng/mL, for organic peroxides between 34 ng/mL and 5 μg/mL. No interference by other compounds was observed when their concentrations were below 10 mg/mL except ethers and phenols.
Conductometric determination of quaternary ammonium salts by sodium perchlorate and vice versa by E. Bottari; P. De Felice; M. R. Festa (pp. 129-132).
A conductometric method is proposed for the determination of quaternary ammonium salts (chloride or bromide), based on the poor solubility of the relative perchlorates. A comparison between expected and found values shows that the method is suitable, rapid, and easy for quantities in the range from 0.2 to 5 g. The error depends on the solubility of the relative perchlorate. The apparent and tentative solubility product of the studied compounds were calculated. The obtained values allowed to propose benzyltributyl ammonium chloride (BTBA Cl) as precipitant for the conductometric titration of perchlorate. This easy, rapid and accurate determination can be used to analyze the perchlorate ion even in concentrated solutions and to determine stability constants for complex formation in aqueous solutions.
Determination of trimethylsilanol in the environment by LT-GC/ICP-OES and GC-MS by R. Grümping; D. Mikolajczak; A. V. Hirner (pp. 133-139).
The combination of element-specific investigation by low temperature gas chromatography coupled on-line with inductively coupled plasma optical emission spectroscopy (LT-GC/ICP-OES) and gas chromatography using mass spectrometry detection (GC-MS), as an additional analytical technique for molecular identification, was employed for the determination of volatile organosilicon species. Gaseous and liquid samples from waste deposit sites, waste composting tanks and sewage-disposal plants were investigated. It was frequently possible to identify the labile silanol compound trimethylsilanol as a dominant silicon species in waste disposal and waste composting gases. The results presented give rise to the assumption that trimethylsilanol is a volatile product of the degradation of organosilicon materials under special environmental conditions.
Wavelet analysis on photoacoustic spectra of degraded PVC by Junjun Mao; Peiyan Sun; Zhongxiao Pan; Qingde Su; Zhang Maosen (pp. 140-142).
Wavelet transform (WT) is introduced successfully to filter simultaneously the noise and the base line in complicated photoacoustic (PA) spectra. As the noise is often at very high frequency and the base line at very low frequency, WT can fully demonstrate its capability of decomposing the signal according to the frequency. After wavelet transform, the relative strength of photoacoustic bands can be easily determined. Thus, WT can be expected as a powerful method in PA spectroscopy for analyzing the formation of polyenes with various conjugated numbers during degradation process.
Supercritical fluid extraction of t-resveratrol and other phenolics from a spiked solid by M. T. Tena; A. Ríos; M. Valcárcel (pp. 143-148).
Supercritical fluid extraction of spiked phenolics including gallic acid, (+)-catechin, (–)-epicatechin, caffeic acid, p-coumaric acid, myricetin, t-resveratrol, quercetin and salicylic acid from an inert support using pure CO2 and methanol-carbon dioxide mixtures was studied. Extraction and collection variables including modifier percentage, extraction temperature, flow rate, extraction time, trap packing and rinse solvent were optimized. The study revealed that the use of methanol as modifier was mandatory. Only the less hydroxylated compounds such as p-coumaric acid, t-resveratrol and salicylic acid could be quantitatively recovered (mean recovery ≥ 95%) from spiked diatomaceous earth. Mean recoveries of more polar phenolic acids and flavonoids such as gallic acid, caffeic acid, catechins and quercetin were between 30% and 70%. Myricetin was not recovered at all.
Assessing the deposition and remobilisation behaviour of metals between river water and river sediment using partial least squares regression by J. W. Einax; O. Kampe; D. Truckenbrodt (pp. 149-154).
Partial least squares regression (PLS) as a method for multivariate data analysis has been applied to environmental data of the German rivers Saale, Ilm and Unstrut. Main aspects of the study are to describe the relationships of the distribution of metals between river water and river sediment using PLS. A simulation of the distribution of metals between the liquid and solid phase by variation of some parameters (e.g. conductivity, DOC, dissolved oxygen, pH, phosphate and suspended matter) is presented and compared with experimental results.
Sequential determination of tin, arsenic, bismuth and antimony in marine sediment material by inductively coupled plasma atomic emission spectrometry using a small concentric hydride generator and L-cysteine as prereductant by Y.-L. Feng; H.-Y. Chen; H.-W. Chen; Li-Ching Tian (pp. 155-157).
A hydride generation system using a small concentric hydride generator combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) was established to determine tin, arsenic, bismuth and antimony in a marine sediment material with L-cysteine as a pre-reductant. Influences of concentrations of three kinds of acids (HCl, HNO3 and HClO4), L-cysteine, and sodium tetrahydroborate(III) as well as sodium hydroxide were investigated. The interferences from transition ions were found to be insignificant for determination of the four elements in presence of L-cysteine. Under optimized conditions the detection limits were 0.6 ng/mL for arsenic(III), 0.8 ng/mL for antimony(III), 1.7 ng/mL for tin(IV), and 1.2 ng/mL for bismuth(III). The method was applied to determine the four elements in standard marine sediment materials and the results were in agreement with certified values.
Improvements in the determination of chlorobenzenes and chlorophenols through a stepwise interlaboratory study approach by P. de Voogt; Eddie A. Maier; Alain Chollot (pp. 158-163).
A systematic quality control programme carried out by a number of laboratories from the European Union and from EFTA countries is described. The programme was designated to improve the analytical state of the art in the determination of selected chlorinated benzenes and chlorinated phenols in different environmental matrices. To that end a stepwise interlaboratory study approach was chosen, analysing, in consecutive order, a clean extract of soil, a raw extract and the soil itself. Eight analytes were selected for the study, i.e. three chlorobenzenes and five chlorophenols. During the programme significant improvements in analytical performance were achieved, as shown by a decrease in within-laboratory coeffficients of variation as well as by acceptable coefficients of variation in the mean value of laboratory means of all analytes in the final matrix analysed, i.e. a natural soil. The results of the programme prompted the European Union to embark upon a pentachlorophenol interlaboratory certification study to produce an industrial soil candidate Certified Reference Material (CRM) [1].
Optimization of digestion methods for sewage sludge using the Plackett-Burman saturated design by I. Lavilla; B. Pérez-Cid; C. Bendicho (pp. 164-167).
The Plackett-Burman saturated factorial design was used to select optimized dissolution conditions for sewage sludge samples. Three different digestion methods were applied: i) microwave oven digestion in a domestic oven with Parr-type reactors; ii) microwave oven digestion with controlled-pressure reactors; iii) pressure bomb reactor heated on a hot plate. The three methods were validated by statistically comparing the metal contents found with the certified ones of the sewage sludge sample (BCR 145R). No significant differences were obtained and the RSD values were lower than 3% in all cases. The metals were determined by flame-AAS. The variables studied were the following: microwave power; digestion time; predigestion; volume of hydrochloric acid; volume of hydrofluoric acid; volume of nitric acid. The operative advantages offered by microwave digestion with controlled-pressure reactors were also considered.
Determination of arsenic, selenium, and antimony in cloud water by inductively coupled plasma mass spectrometry by Robert C. Richter; Kamal Swami; Steven Chace; Liaquat Husain (pp. 168-173).
The capability of inductively coupled plasma mass spectrometry in determining trace levels of As, Se, and Sb in cloud water was evaluated. Preliminary studies focused on identifying and eliminating potential interferences in the cloud water matrix, the choice of appropriate internal standards, and system optimization. The detection limits for As, Se, and Sb were 20, 100, 20 pg/mL using pneumatic nebulization, and 5, 25, 5 pg/mL, respectively, using ultrasonic nebulization with a precision of better than 5% RSD. The accuracy was demonstrated by the analysis of a NIST commercial reference material, SRM 1643d. In all cases, the results from ICP-MS analysis agreed within 4% of the certified values. Comparative analysis of cloud water samples obtained from a site downwind from large pollution sources (Whiteface Mountain, New York) and Changlagali Pakistan, a rural mountain peak, was carried out by hydride generation atomic absorption (HGAA) spectrometry. There was excellent agreement between the ICP-MS and HGAA results.
Homogeneous immunoassay for the detection of trinitrotoluene (TNT) based on the reactivation of apoglucose oxidase using a novel FAD-trinitrotoluene conjugate by M. Dosch; M. G. Weller; A. F. Bückmann; R. Niessner (pp. 174-178).
A flavin adenine dinucleotide-trinitrotoluene derivative (FAD-TNT) was synthesized by coupling N 6-(2-aminoethyl)-FAD covalently to the N-hydroxysuccinimidyl ester of trinitrophenyl-γ-aminobutyric acid and characterized by negative-ion electrospray-ionization mass spectrometry (ESI-MS) after purification by reversed-phase HPLC. Free FAD-TNT can be detected at very low levels by recombination with apoglucose oxidase, since the FAD-TNT-glucose oxidase complex is enzymatically active. On the contrary, if FAD-TNT has been bound by an anti-TNT antibody, the conjugate cannot recombine with apoglucose oxidase any more. Based on these two phenomena, a homogeneous apoenzyme reactivation immunoassay system (ARIS) was developed for the detection of TNT. No separation step is needed in this assay. Proportionality between the TNT concentration and enzyme activity was demonstrated with a detection limit of 5 μg/L TNT.
Automation of a heterogeneous enzyme immunoassay for atrazine. Comparison of three immobilization supports by M. A. González-Martínez; S. Morais; R. Puchades; A. Maquieira; M. P. Marco; D. Barceló (pp. 179-184).
Intensive agriculture associated with the use of large amounts of different pesticides, together with the growing concern about the potential contamination of ground water, have brought about the need for developing fast screening methods. This work presents the automation of an enzyme-linked immunosorbent assay for atrazine by means of a flow-through system. Three different solid supports for antibody immobilization were compared in a direct competitive assay format. Sensitivity reached in all cases was below the maximum level allowed in the EU (100 ng L–1). Cross-reactivity of atrazine-related compounds was also studied. The performance of the different supports is discussed regarding sensitivity and immunosurface regeneration.
Trace enrichment, chromatographic separation and biodegradation of cytostatic compounds in surface water by Thekla Kiffmeyer; Hans-Jürgen Götze; Martin Jursch; Uwe Lüders (pp. 185-191).
A trace analytical procedure for the cytostatic drugs carmustine, chlorambucil, cisplatin, cyclophosphamide, cytarabine, etoposide, 5-fluorouracil, melphalan, methotrexate, and vinblastine was developed in order to evaluate the environmental hazards of these drugs in clinical waste water and sewage treatment plants. The analysis was performed using solid phase extraction with subsequent HPLC separation and quantitative determination by gradient elution techniques with DAD and fluorescence detection. Detection limits after the clean-up and enrichment procedure vary from 0.002 to 0.2 mg/L. A simulation of the degradation processes under conditions as close as possible to those in a real sewage plant showed that cisplatin and cyclophosphamide are not biodegradable, but cytarabine and 5-fluorouracil are biodegradable in different magnitudes. The biodegradation process of methotrexate is combined with the generation of the toxic and persistent degradation product 7-hydroxymethotrexate.
Determination of persistent organochlorine compounds in blood by solid phase micro extraction and GC-ECD by Lars Röhrig; Michael Püttmann; H.-U. Meisch (pp. 192-196).
Biomonitoring of persistent organochlorine compounds in blood using the solid phase microextraction technique (SPME) and gas chromatography with electron capture detection (GC-ECD) is described. Polar substances as tri-, tetra- and penta-chlorophenols are analyzed simultaneously with less polar compounds such as hexachlorobenzene (HCB), α-, β-, and γ-hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its derivatives and with some important congeners of the polychlorinated biphenyls (PCB). No derivatization is needed for the determination of the phenolic compounds. The results show a good reproducibility down to the lower μg/L-region. The method is very fast and of low cost compared to the classic extraction and determination procedures.
Determination of the cadmium and copper content inherent to metallothionein by B. Raspor; S. Kozar; J. Pavičić; D. Jurič (pp. 197-200).
The reliability of the voltammetric determination of the cadmium and copper content (at pH 1.0), inherent to metallothionein (MT) isolated from the digestive gland of Mytilus galloprovincialis, was investigated. An artifact signal enhancement of copper, caused by the cupric-thionein complex adsorption at the mercury electrode, was established. This artifact was removed by UV-digestion of the sample for 15–20 h prior to analysis. A similar artifact was not detected for cadmium, because at this pH the cadmium-thionein complex has dissociated, and cadmium exists in the ionic form. Therefore, the voltammetric analysis of the cadmium content can be performed directly at pH 1.0, without prior UV-digestion of the sample.
A routine method for the determination of retronecine by Jeannette T. Hovermale; A. Morrie Craig (pp. 201-206).
A method for the routine determination of the necine base retronecine from biological matrices is described, using gas chromatography for quantification. The biological matrices studied included blended sheep whole rumen fluid and bacterial growth media. The structurally similar compound 2,6-dimethoxypyridine was utilized as an internal standard. Prior to gas chromatography, the bis(heptafluorobutyrate) derivatives of both compounds were formed. The relative percent recoveries of retronecine and the internal standard were 73% and 82%, respectively. The detection limit of retronecine in blended whole rumen fluid was found to be 0.09 μg/mL, and 0.02 μg/mL in bacterial growth media. The precision of the peak area ratio (retronecine to internal standard) was 10% from blended whole rumen fluid, and 14% from bacterial growth media. This method was used to analyze samples from viable cultures incubated with retronecine.
Experimental studies for the characterization of analytical performance in axially-observed inductively coupled plasma atomic emission spectrometry by W. Schrön; A. Liebmann (pp. 207-210).
Investigations were carried out on the optimization of excitation and projection conditions of the axially-observed inductively coupled plasma (ICP) concerning simultaneous measurements. For minimized background equivalent concentration (BEC) it can be shown that the optimal excitation conditions of the atomic and ionic lines also vary in the case of axial plasma observation. A relationship was confirmed between the high frequency power and the excitation energy of the analytical lines. The main contribution of this work is the displacement of the axial viewing inductively coupled plasma by means of an x,y,z sliding carriage.The displacement showed that under the selected experimental conditions the point of observation is spatially identical for all analytical lines.
Simultaneous determination of Co(II), Cr(VI), Ni(II) and Pb(II) in water by solvent extraction and high-field 1H NMR Spectrometry by S. C. F. Au-Yeung; S. Y. Fan; J. C. Yu; W. L. A. K. Chiu (pp. 210-213).
A novel analytical approach is described that combines the preconcentration power of solvent extraction with the resolution and sensitivity of a 500 MHz 1H NMR spectroscopic detection method for the quantitative determination of metals. Co(II), Cr(VI), Ni(II) and Pb(II) in water are extracted into chloroform as dithiocarbamate complexes. By decoupling the protons and employing a solvent-induced shift method, the 1H NMR spectrum containing the dithiocarbamate complexes of Co(II), Cr(VI), Ni(II) and Pb(II) is fully resolved at CDCl3/ C6D6 below 40%/60%. The detection limits for Co(II), Cr(VI), Ni(II) and Pb(II) are estimated to be 0.12, 0.073, 0.11 and 0.27 μg/mL, respectively, in the sample solution.
Comparison of hexamethylenedithiocarbamate and tetramethylenedithiocarbamate as flotation reagents for the concentration of zinc by Gorica Pavlovska; Trajče Stafilov; Katarina Čundeva (pp. 213-216).
A procedure for zinc flotation separation from fresh water prior to its determination by atomic absorption spectrometry (AAS) has been developed. Hexamethyleneammonium hexamethylenedithiocarbamate (HMA-HMDTC) added to the first precipitate collector of hydrated Fe(III) oxide (Fe2O3· xH2O) gives the second precipitate collector of Fe(HMDTC)3. After addition of a surfactant, the precipitate of collectors is separated from the water phase by a stream of air bubbles, dissolved by strong acid and the solution then tested by AAS. The experimental parameters (amount of collector used, pH, ionic strength, type of foaming reagent, ζ potential, induction time etc.) affecting the flotation efficiency were optimized. At a pH of 6, Zn is separated quantitatively (98.5%) by addition of 5 mg Fe(III) and 3 mL 0.1 mol/L HMA-HMDTC to the sample. Results are compared with those obtained by ammonium tetramethylenedithiocarbamate.
Low-blank digestion of geological samples for platinum-group element analysis using a modified Carius Tube design by M. Rehkämper; Alex N. Halliday; Roy F. Wentz (pp. 217-219).
We have developed a modified Carius Tube design that permits the low-blank digestion of geological samples prior to platinum-group element analysis. The new Carius Tubes incorporate a liner of high-purity quartz glass that retains the sample and acids during the digestion procedure. This dramatically reduces the comparatively high Pt blank associated with dissolutions in conventional Carius Tubes. Using the new Carius Tube design we are able to achieve total procedural blanks for the determination of the PGE in geological samples that are at the 1–15 pg/g level for Ru, Pd, Ir and Pt. This constitutes a reduction of blank values by a factor of ∼10–100 compared to standard NiS fire assay sample preparation techniques.
Determination of trace amounts of Galaxolide® (HHCB) by HPLC by W. Schüssler; Lutz Nitschke (pp. 220-221).
An analytical method for the determination of trace amounts of Galaxolide® (HHCB) by HPLC is presented. It is based on the separation of HHCB in different samples by a C18-column and a gradient elution by water and acetonitrile, both containing some acetic acid. The detection is carried out with a combination of a fast scanning UV detector and a fast scanning fluorescence detector. The fluorescence detection limit is 5 μg/L HHCB without sample pretreatment. HHCB adsorbed on solids or suspended solids can be extracted by ethanol.