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Analytical and Bioanalytical Chemistry (v.371, #8)
No Title by Katrin Cziesla; Bernhard Platzer; Michael Okruss; Stefan Florek; Matthias Otto (pp. 1043-1046).
The coupling of a near-infrared Echelle spectrometer (NIRES) with a gas chromatograph for element-selective detection is introduced. The miniaturized capacitive plasma device is operated at a frequency of 40.68 MHz and is mounted directly on an Hewlett–Packard HP6890 GC. First results with a mixture of halogenated standard compounds are presented and discussed in terms of the advantages and problems with this system.
A long-term validation of the modernised DC-ARC-OES solid-sample method by K. Flórián; J. Haßler; O. Förster (pp. 1047-1051).
The validation procedure based on ISO 17 025 standard has been used to study and illustrate both the long-term stability of the calibration process of the DC-ARC solid sample spectrometric method and the main validation criteria of the method. In the calculation of the validation characteristics depending on the linearity(calibration), also the fulfilment of predetermining criteria such as normality and homoscedasticity was checked. In order to decide whether there are any trends in the time-variation of the analytical signal or not, also the Neumann test of trend was applied and evaluated. Finally, a comparison with similar validation data of the ETV-ICP-OES method was carried out.
No Title by Björn Knauthe; Matthias Otto (pp. 1052-1056).
The behavior of phosphorus, sulfur and carbon in the argon–ICP–OES was systematically investigated for a wide range of nebulizer gas flows and observation heights. Five lines of phosphorus, four lines of sulfur and three lines of carbon, which have analytical usable detection limits, were taken into consideration. The further parameter set was inspired by the needs of every-day-analysis in the laboratory, especially the low integration time that is necessary for analysis of large amounts of samples. For each element line a signal-to-noise plot was obtained with a method described earlier. The optimum conditions for the combined analysis were determined from signal-to-noise plots of those element lines with the lowest detection limits. The lowest detection limits for phosphorus (0.13 mg/L) and carbon (0.01 mg/L) are useful for solving many analytical problems. However, even the best detection limit for sulfur (2.97 mg/L) is only of limited use without further preconcentration. A major problem was the background of carbon, most probably from carbon dioxide, which increased the available detection limit to about 0.04 mg/L. Surprisingly, the best detection limits were obtained at very low observation heights, which were only a couple of millimeters above the load coil. Fortunately, all elements showed a similar behavior and so the detection limits at compromise conditions were only slightly higher compared with the single-element detection limits.
No Title by Christian Ludwig; Harald Lutz; Jörg Wochele; Samuel Stucki (pp. 1057-1062).
"Thermal desorption experiments" were carried out during which heavy metal evaporation was studied by on-line monitoring. This could be achieved by the use of a tubular furnace connected to a heavy metal detector, i.e. an ICP-OES (inductively coupled plasma optical emission spectrometer), by a specially designed and patented interface. The spectrograms typically had a time resolution of four different elements per minute using a conventional (sequentially operating) ICP-OES. This study shows how thermo-desorption spectrometry (TDS) can be applied to study the evaporation of high boiling substances, such as heavy metal and alkali metal compounds. The future scope of the method is discussed.
No Title by Tobias Bundschuh; Jong-Il Yun; Roger Knopp (pp. 1063-1069).
The application of laser-induced breakdown detection (LIBD) as a new and powerful particle-analyzing technique for the determination of solubility data by monitoring initial colloid generation, when the metal ion concentration just exceeds the solubility at a given pH value, is investigated. Laser-induced breakdown spectroscopy (LIBS) is used for selective analysis of an aqueous suspension of lanthanide oxide particles in the presence of the respective lanthanide aquo ion. The detection limit for aquo ion and oxide particle is determined. On the basis of the different detection limits, the LIBS technique is used to study the formation of hydroxide colloids in aqueous solution by varying the pH value until the solubility limit is exceeded. LIBS enables both qualitative and quantitative monitoring of particle formation without artifacts arising from other contaminants. LIBD and LIBS are described and compared. The advantages and disadvantages of the methods for the determination of solubility data are discussed.
No Title by O. Schulz; P. Heitland (pp. 1070-1075).
A new axially viewed ICP optical emission spectrometer featuring an argon-filled optic and CCD detectors was evaluated for the application of prominent spectral lines in the 125–180 nm range. This wavelength range was investigated for several analytical applications of inductively coupled plasma optical emission spectrometry (ICP–OES). There are different advantages for the application of spectral lines below 180 nm. A number of elements, such as Al, Br, Cl, Ga, Ge, I, In, N, P, Pb, Pt, S and Te, were found to have the most intense spectral lines in the wavelength range from 125–180 nm. Compared with lines above 180 nm higher signal-to-background ratios were found. Low limits of detection using pneumatic nebulization of aqueous solutions for sample introduction were calculated for Al II 167.080 nm (0.04 µg L–1), Br I 154.065 nm (9 µg L–1), Cl I 134.724 nm (19 µg L–1), Ga II 141.444 nm (0.8 µg L–1), Ge II 164.919 nm (1.3 µg L–1), I I 142.549 nm (13 µg L–1), In II 158.583 nm (0.2 µg L–1), P I 177.500 nm (0.9 µg L–1), Pb II 168.215 nm (1.5 µg L–1), Pt II 177.709 nm (2.6 µg L–1), S I 180.731 nm (1.9 µg L–1) and Te I 170.00 nm (4.6 µg L–1). Numerous application examples for the use of those lines and other important spectral lines below 180 nm are given. Because of fewer emission lines from transition elements, such as Fe, Co, Cr, lines below 180 nm often offer freedom from spectral interferences. Additional lines of lower intensity for the determination of higher elemental concentrations are also available in the vacuum ultraviolet spectral range. This is specially useful when the concentrations are not in the linear range of calibration curves obtained with commonly used lines.
No Title by Krzysztof Kilian; Krystyna Pyrzyñska (pp. 1076-1078).
The preconcentration of some divalent metal ions by complexation with carboxyphenylporphyrin (TCPP) and retention on conventional anion-exchange resins and a non-ionic sorbent was examined. Two different procedures – ligand in solution or immobilised on the solid sorbents – were evaluated as a function of pH. The selectivity order for metal ions on the TCPP-loaded resin Amberlite IRA-904 was established as: Pb(II)>Ni(II)>Cu(II)>Cd(II)>Mg(II).
Performance of permanent iridium modifier in the presence of corrosive matrix in graphite furnace atomic absorption spectrometry by Marek Piaścik; Ewa Bulska (pp. 1079-1082).
The influence of up to 16% HNO3, 28% HCl, and the mixture of both acids in aqua regia on the analytical performance of electrodeposited modifiers (Ir or Ir+Pd) was evaluated and discussed. Cadmium was used as an example of volatile elements often determined by graphite furnace atomic absorption spectrometry (GF AAS). In the presence of HCl, the maximum pyrolysis temperature that could be applied was found to be 600 °C. In the presence of HNO3 and aqua regia, both modifiers stabilized cadmium up to 800 °C. The long-term performance of electrodeposited Ir or Ir+Pd was not influenced by mineral acids; moreover the tube lifetime was significantly prolonged compared with a non-modified tube.
No Title by Michael W. Pfaffl; Leendert A. van Ginkel; John D. McEvoy; Guy Maghuin-Rogister; Heinrich H. Meyer (pp. 1086-1091).
Within the EU Standards, Measurement and Testing Program (SMT) two clenbuterol reference materials (RMs) were developed. Since clenbuterol readily accumulates and is slowly depleted from pigmented tissues such as the retina, homogenized eye liquid content is the most sensitive tissue for the detection of clenbuterol misuse. Therefore, both of the RMs were produced from bovine eye matrix: a negative control – RM 673 eye reference material, clenbuterol free (<0.50 µg/kg eye matrix) and a positive – RM 674 eye reference material containing clenbuterol (~10 µg/kg eye matrix). Eyes were sampled from 103 German Simmental cattle and the inner liquid content was homogenized to a wet homogenized liquid content (HLC). This clenbuterol negative pool was divided into two sub-pools, one of which was spiked with clenbuterol to a final concentration of 10 µg clenbuterol/kg HLC. Of each pool exactly 2.0±0.01 g (±0.5%) portions were weighed into 790 containers. Lyophilization of the 1580 containers was performed in one batch. Parameters for the filling of containers, dry matter content, and residual moisture were in accordance with EU requirements. A three-year stability study and two homogeneity studies at various storage temperatures (–60 °C, –20 °C, +4 °C, +20 °C, and +37 °C) were performed. Low variation was observed within all of the homogeneity studies, proving that each of the RMs were homogeneous and that this was independent of storage temperature and storage time. In the stability studies, measured clenbuterol concentrations remained constant for RM 673 under the detection limit at 0.15±0.01 µg clenbuterol equivalent/kg HLC (n=110) and were also constant for RM 674 at 11.21±0.15 µg clenbuterol/kg HLC (n=150; measured as duplicates). These studies demonstrate that clenbuterol-containing and clenbuterol-free RMs in bovine eye matrix can be successfully produced. Based on the results described above, it is concluded that both RMs may be suitable as candidates for certification.
Keywords: Clenbuterol Cattle Eye matrix Reference material Standards CRM
No Title by Michael W. Pfaffl; Leendert A. van Ginkel; John D. McEvoy; Guy Maghuin-Rogister; Heinrich H. Meyer (pp. 1092-1097).
The certification by inter-laboratory testing of two candidate reference materials (RMs) for the mass concentration of the anabolic agent clenbuterol in bovine eye material is described: RM 674 with ca 10 µg clenbuterol per kg of eye matrix and RM 673 clenbuterol-free eye matrix as the negative control (<0.50 µg kg–1). Both candidate RMs were certified by eleven EU laboratories, and sixty-six accepted replicate measurements were included in the "Certification Study". The precision of the measurement process was assessed by calculation of the standard variation determined within each laboratory during the certification step. The study was performed according to the "Guidelines for the production and certification of BCR reference materials" and to "ISO guide 31, 33, and 35". The certified clenbuterol mass concentration for clenbuterol-free eye material CRM 673 (calculated on the basis of clenbuterol as the free base) was <0.50 µg kg–1. The corresponding concentration for clenbuterol-containing eye material CRM 674 was 9.42±0.88 µg kg–1. These certified values are very close to the desired target concentration of <0.5 µg kg–1 and ca 10 µg kg–1. This study has demonstrated that successful certification of clenbuterol-containing and clenbuterol-free bovine eye materials is possible.
Emission of M2X+ cluster ions in thermal ionization mass spectrometry in the presence of graphite by Y. Xiao; H. Wei; W. Liu; Q. Wang; Y. Zhou; Y. Wang; H. Lu (pp. 1098-1103).
The emission of M2X+ cluster ions in thermal ionization mass spectrometry when graphite is loaded on the heating filaments was studied. The emission model of non-reductive thermal ionization of graphite was preliminarily discussed and factors influencing the thermal emission of M2X+ ions were investigated. The results show that the intensities of M2X+ cluster ions are related to ionic radius and crystal lattice energy, and possibly also to the solvation energies of ions. The intensities of M2Cl+ (M stands for K, Rb, and Cs) cluster ions, the M2Cl+/M+ ratios, and the 37Cl/35Cl ratios determined from M2Cl+ ion measurement usually increase with measurement time. The variation of the 37Cl/35Cl ratios determined from Cs2Cl+ ion measurement is lower than those based on K2Cl+ and Rb2Cl+ ion measurement, indicating the lowest isotopic fractionation.
No Title by Mojtaba Shamsipur; Sayed Kazemi; Hashem Sharghi; Khodabakhsh Niknam (pp. 1104-1108).
A PVC membrane sensor for the Cs+ ion based on 1,5-diaza-2,3,4-naphthyl-8,11,14-trioxacyclohexadecane-6,16-dione (L) has been prepared. The sensor has a linear dynamic range of 5.0×10–1-6.9×10–6 mol L–1, a Nernstian slope of 59.5±0.8 mV decade–1, and a detection limit of 4.7×10–6 mol L–1. It has a fast response time of <15 s and can be used for at least 8 weeks without any considerable divergence in potentials. The selectivity of the proposed electrode relative to alkali, alkaline earth, and transition metal ions was comparatively good. The electrode could be used in the pH range 4.5–11.0.
Direct determination of nitrite traces in high ionic-strength samples by electrostatic ion chromatography using diluted acid solutions as eluent by Wenzhi Hu; Kiyoshi Hasebe; Ming-Yu Ding; Kazuhiko Tanaka (pp. 1109-1112).
An ion-chromatographic (IC) system with high selectivity for separation of nitrite is described. It is analogous to the EIC (electrostatic IC) previously reported and was established using 3-(N,N-dimethylstearylammonio)propanesulfonate (C23H49NO3S, a sulfobetaine type of zwitterionic surfactants) as the stationary phase and dilute aqueous HCl solutions as the mobile phase. Five inorganic anions, sulfate, chloride, bromide, nitrate, and nitrite were chosen as the model analytes and were analyzed using this EIC system. Sulfate was always eluted first, followed by chloride, bromide and nitrate. Nitrite, however, could be eluted either before or after nitrate, depending on the concentration of HCl in the eluent. An elution order nitrate3 mmol L–1 HCl as the eluent. For nitrite the detection limit was better than 2.1×10–7 mol L–1 (100 µL sample injection volume, S/N=3, UV at 210 nm). Bromide and nitrate could also be separated under these HPLC conditions. The detection limit for bromide was 7.2×10–8 mol L–1 and for nitrate 6.5×10–8 mol L–1. Both nitrite and nitrate in real seawater samples were successfully determined with direct sample injection using this EIC system.
No Title by Behzad Haghighi; Abdollah Tavassoli (pp. 1113-1118).
Two flow-injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 µL) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd–Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O2 carrier gas. The gaseous phase is separated from the liquid phase using a gas–liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV–visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd–Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd–Cu reduction method, up to 330 µg of nitrate was determined. The limit of detection was 2.97 µg nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 µg nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd–Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample.
No Title by P. Bruno; M. Caselli; G. de Gennaro; A. Traini (pp. 1119-1123).
A multivariate statistical method has been applied to apportion the atmospheric pollutant concentrations measured by automatic gas analyzers placed on a mobile laboratory for air quality monitoring in Taranto (Italy). In particular, Principal Component Analysis (PCA) followed by Absolute Principal Component Scores (APCS) technique was performed to identify the number of emission sources and their contribution to measured concentrations of CO, NOx, benzene toluene m+p-Xylene (BTX). This procedure singled out two different sources that explain about 85% of collected data variance.
Coupling pervaporation to AAS for inorganic and organic mercury determination. A new approach to speciation of Hg in environmental samples by Consuelo Fernandez-Rivas; Riansares Muñoz-Olivas; Carmen Camara (pp. 1124-1129).
The design and development of a new approach for Hg speciation in environmental samples is described in detail. This method, consisting of the coupling of pervaporation and atomic absorption spectrometry, is based on a membrane phenomenon that combines the evaporation of volatile analytes and their diffusion through a polymeric membrane. It is proposed here as an alternative to gas chromatography for speciation of inorganic and organic Hg compounds, as the latter compounds are volatile and can be separated by applying the principles mentioned above. The interest of this method lies in its easy handling, low cost, and rapidity for the analysis of liquid and solid samples. This method has been applied to Hg speciation in a compost sample provided by a waste water treatment plant.
Determination of chromium in river waters by electrothermal atomic absorption spectrometry with preconcentration on a tantalum wire by Nurul Md. Amin; Hidetoshi Okada; Syn-ichi Itoh; Tohru Suzuki; Satoshi Kaneco; Kiyohisa Ohta (pp. 1130-1133).
The preconcentration of chromium on tantalum wire followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer is described. The preconcentration is accomplished by adsorbing chromium on a tantalum wire. The optimal immersion time was 3 min. The best pH for chromium adsorption was 3. Under optimal conditions, the detection limit was 15 pg mL–1 (3×S/N). The effects on the preconcentration of chromium by large amounts of contaminants were evaluated. Even though matrix elements existed in 103–104-fold excess in water, the chromium absorption signal was not affected by the matrix elements. The method with preconcentration on tantalum wire was applied to the determination of chromium in river water.
Spectrophotometric determination of some pesticides in water samples after preconcentration with Saccharomyces cerevisiae immobilized on sepiolite by A. Tunçeli; H. Bağ; Rehber A. Türker (pp. 1134-1138).
A sensitive and selective method for the preconcentration and determination of carbaryl, chlorpyrifos, linuron, and thiram was developed. The column sorption method was used for the preconcentration studies. Several parameters, such as amount of sorbent, pH, flow rate, volume of elution solution, and interferences, that can influence the retention of pesticides on Saccharomyces cerevisiae immobilized on sepiolite were investigated. Results showed that it was possible to achieve quantitative analysis when the sample pH was in the range 4–6 for carbaryl and thiram, 4–8 for linuron and 6 for chlorpyrifos using 100 mL of sample solution containing 20 µg of pesticide and 5 mL of eluent. Recoveries of carbaryl, chlorpyrifos, linuron, and thiram were 93.2±0.4%, 97.1±0.3%, 98.5±0.4%, and 96.1±0.2%, respectively, at 95% confidence level under optimum conditions. The capacity of the sorbent was found to be 41, 28, 35, and 46 mg g–1 for carbaryl, chlorpyrifos, linuron, and thiram, respectively. Saccharomyces cerevisiae immobilized on sepiolite is suitable for repeated use without loss of capacity up to twenty five cycles. The pesticides studied have been determined in river water with high precision and accuracy.
No Title by M. Felipe-Sotelo; A. Carlosena; E. Fernández; P. López-Mahía; S. Muniategui; D. Prada (pp. 1139-1145).
Five modifiers were tested for the direct determination of cobalt in coal fly ash and slag by ultrasonic slurry-sampling electrothermal atomic absorption spectrometry (USS–ETAAS).The furnace temperature programs and the appropriate amount for each modifier were optimized to get the highest signal and the best separation between the atomic and background signals. Nitric acid (0.5% v/v) was the most adequate chemical modifier for cobalt determination, selecting 1450 °C and 2100 °C as pyrolysis and atomization temperatures, respectively. This modifier also acts as liquid medium for the slurry simplifying the procedure. The remaining modifiers enhanced the background signal, totally overlapped with cobalt peak. The method optimized gave a limit of detection of 0.36 µg g–1, a characteristic mass of 13±1 pg and an overall-method precision which is highly satisfactory (<7%, RSD). The method was validated by analyzing two certified coal fly ash materials, and satisfactory recoveries were obtained (83–90%) and no statistical differences were observed between the experimental and the certified cobalt concentrations. Additionally, certified sediment, soil and urban particulate matter were assayed; again good results were obtained. The developed methodology was used to determine cobalt in several coal combustion residues from five Spanish power plants.
No Title by F. Reiff; M. Bartels; M. Gastel; H. Ortner (pp. 1146-1153).
Four contemporary forgeries of ancient gold coins were investigated regarding techniques used for gilding, and the composition of the gold cover and the base metal core. The forged coins are a Daric of the Persian Empire, a Gold Stater in the name of Alexander, and two Solidi of the late Roman Empire. A combination of modern analytical methods such as Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA), X-Ray Fluorescence Spectrometry (XRF), and Secondary-Ion Mass Spectrometry (SIMS) was used. The results demonstrate that the coins represent the main three technologies of gilding used in antiquity. The core of the Daric is a silver Siglos, plated by leaf gilding. The Gold Stater was forged by foil gilding using a silver core. The Roman Solidi have a core of either silver or copper and were plated by fire gilding. On account of our results it is possible to compare the forgers' profits made by use of the different technologies of forging.
No Title by Han-wen Sun; Jing Ha; Jian-min Sun; Li-li Yang; De-qiang Zhang (pp. 1154-1157).
Fundamentals of derivative hydride-generation atomic absorption spectrometry (DHGAAS) are described. A linear relationship was obtained between the derivative absorbance and the concentration of analysis in a sample. The new DHGAAS method was applied to the determination of traces of lead in water. The conditions affecting the derivative absorbance of lead were evaluated and optimized. The detection limit and sensitivity of the proposed method were 26 times and 8.8 times better, respectively, than those of conventional hydride-generation atomic absorption spectrometry. The characteristic concentration (for a derivative absorbance of 0.0044) and detection limit (3σ) for lead were 0.017 and 0.096 ng mL–1, respectively, for a 2 mV min–1 sensitivity range setting. The recovery range was 92.5–103%.
Direct determination of boron and zirconium in ceramic materials by flame atomic absorption spectrometry after alkali sintering and fusion by M. Mihaljevič; O. Šebek; E. Lukešová; A. Bouzková (pp. 1158-1160).
Both boron and zirconium are present in ceramic materials as major silica components and have to be determined for quality control in the ceramic industry. For boron determination, sintering with a mixture of Na2CO3 and ZnO is proposed for decomposition of samples. For zirconium determination, acid digestion using an HF–HClO4 mixture and subsequent fusion with NaKCO3 and H3BO3 is proposed as decomposition step. The AAS absorbance signal of these elements is suppressed by the fusion elements in the samples. Therefore, the calibration solutions for both B and Zr must contain an appropriate concentration of sodium, sodium–potassium, and boron salts. An AlF3 solution was used for signal enhancement and improving the linearity of the Zr calibration curve. The methods proposed are well suited for the determination of higher concentrations of both boron and zirconium in silicate samples.