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Analytical and Bioanalytical Chemistry (v.362, #4)
Optical waveguide sensors in analytical chemistry: today’s instrumentation, applications and trends for future development by R. A. Potyrailo; S. E. Hobbs; G. M. Hieftje (pp. 349-373).
Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered.
Minimising the risk of some systematic errors by the use of the single vessel principle for cold vapour atomic absorption spectrometric determination of mercury in biological solids by H. S. Dhindsa; A. R. Battle; J. Mierzwa (pp. 374-377).
The suitability of the single vessel principle (performing all steps of an analytical procedure in one vessel) for cold vapour atomic absorption spectrometric determination of mercury in biological solids was evaluated. The single vessel method gave a lower mean blank level with better precision, hence lower detection limits, as compared to the conventional method. The determination of total mercury in biological standard reference materials by the single vessel method also produced significantly higher mercury values and better precision than the conventional method. However, the mercury concentrations obtained in certified reference materials by the use of both methods were close to the mean certified values. Moreover, the use of the single vessel method is cost effective, rapid and environment friendly. The use of the single vessel technique is therefore recommended for accurate and reliable determination of mercury in biological solids.
Determination of the hydride concentration in alkyldiboranes(6) by 11B NMR spectroscopy – Reduction of inorganic selenium and tellurium compounds by B. Wrackmeyer; Hans-Jörg Schanz; Wilhelm Schüßler; Roland Köster (pp. 378-381).
As an alternative to volumetric analysis, 11B NMR spectroscopy can be used to determine the hydride concentration and the relative amount of different active hydride species in mixtures of alkyldiboranes(6) (alkyl = Et, Pr). Inorganic selenium(IV) compounds react with propyldiboranes(6) at first to give elemental selenium (hydride number HN = 4) and after prolonged heating at 130 °C to selenides (HN = 6). In contrast, tellurium(IV) and tellurium(VI) compounds are reduced only to elemental tellurium.
Analysis of chlorine and other halogens by activation with photons and neutrons by K. Wagner; W. Görner; M. Hedrich; P. Jost; C. Segebade (pp. 382-386).
The analysis of halogens in various matrices is described. Activation analysis with mainly high energy bremsstrahlung (PAA) and pile neutrons (NAA) was applied. In the case of chlorine, fast procedures were worked out requiring not more than 100 min for one determination. The particular problems of fluorine analysis are discussed. The described techniques were applied for the following cases: Determination of total chlorine resp. bromine in oil samples; determination of chlorine in wood, glasses and TiN powders; determination of iodine in ZnSe single crystals using instrumental photoactivation.The limits of detection are: (interference-free in μg/g) F: 0.03/–; Cl: 0.1/0.05; Br: 0.04/0.003 and I: 0.1/0.01 using PAA/NAA. Activation analysis, being independent upon the chemical status of the analyte and usually less affected by blank problems has been found to be a useful complement to conventional chemical analysis.
Optosensing of hydrochloric acid based on the fluorescence quenching of a flavone copolymer by Wanhui Liu; Jianghong Tang; Ying Wang; Guoli Shen; R. Yu (pp. 387-390).
An optical fiber sensor for the continuous determination of hydrochloric acid is presented. It is based on the fluorescence quenching of a flavone containing copolymer membrane by hydrochloric acid. The quenching efficiency is greatly enhanced in the presence of Fe(III). This enhancement is attributed to the primary inner filter effect, as well as the formation of a complex between the 4′-N,N-dimethylaminoflavone group in the copolymer and the Fe(III) species extracted from hydrochloric acid solution. The optical response is linear and reversible for 0.10–6.00 mol L–1 HCl with a response time of the order of a second. The standard deviations for repeated alternative measurements of 0.20 and 2.00 mol L–1 hydrochloric acid are 0.32% and 0.46% (n = 10), respectively, indicating a good reproducibility. Because of the covalently bonding of the dye to polymer, the sensor exhibits also a good stability. Selectivity has also been evaluated for some potential interferents. The sensor in conjunction with a flow-injection system can be used for on-line determination of hydrochloric acid.
Determination of 99Tc in bentonite clay samples using inductively coupled plasma mass spectrometry by H. Ramebäck; Y. Albinsson; M. Skålberg; U. B. Eklund (pp. 391-394).
A method was developed for the determination of 99Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS. The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser, the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection.
Trace analysis of high-purity copper by total reflection X-ray fluorescence spectrometry by Hitoshi Yamaguchi; Sinji Itoh; Shukuro Igarashi; Kunishige Naitoh; Ryosuke Hasegawa (pp. 395-398).
Total reflection X-ray fluorescence (TXRF) analysis after the separation of matrix element was studied for the determination of trace impurity elements (Ca, Sc, V, Cr, Mn, Fe, Co, Ni and Zn) in high purity copper. Matrix copper was removed by electrolysis (0.2 A, 8 h) of a nitric acid solution. A 10 μL aliquot of the remaining solution of the electrolysis was dropped on a silicon-wafer sample-carrier and dried in a vacuum. This was repeated five times and the precipitate of five 10 μL-aliquots was analyzed by TXRF using a W-Lβ beam with an incident angle of 0.05 °. TXRF analytical values were obtained by using relative sensitivity factors of the analytes to the internal standard element (Pd). Detection limits of the analytes ranges from 0.077 ng for Zn to 0.785 ng for Ca.
Flow-injection spectrofluorimetric determination of ethylenethiourea by Tomás Pérez-Ruiz; Carmen Martínez-Lozano; Virginia Tomás; Antonio Sanz; Jesús Martín (pp. 399-403).
A flow-injection configuration is proposed for the fluorimetric determination of ethylenethiourea. The procedure is based on the inhibitory effect of ethylenethiourea on the oxidation of thiamine to thiochrome by mercury(II). A linear calibration graph was obtained between 0.1 and 2.0 μg mL–1, with a sampling rate of 40 samples per hour and a relative standard deviation of about 1.11%. The usefulness of the method was tested for the determination of ethylenethiourea residues in water, milk, potatoes, pear, grape and apple.
Calculation of the polychlorinated terphenyl congener distribution and gas chromatographic retention behavior of selected single standards on four stationary liquid phases by Gerald Remberg; Pat Sandra; Wolfgang Nyiry; Norbert Winker; A. Nikiforov (pp. 404-408).
The distribution of the 8557 theoretically possible structures of polychlorinated terphenyls (PCT) over the different degrees of chlorination and basic terphenyl backbones has been calculated and is presented in detail. As congeners missing chlorine atoms in an ortho position are suspected to be as noxious to organisms as dioxins, the number of these congeners is specified as well. The gas chromatographic retention behavior of 14 PCT single standards is studied on four stationary liquid phases for capillary columns (HP-Ultra 1, HP-5MS, RSL-300 and Polycarbonate) relative to 2,2′,3,4,4′,5,5′-heptachlorobiphenyl and shows no consequent separation of PCT in terms of the degree of chlorination. Individual congeners have been assessed for their suitability as internal standards in PCT analysis.
FTIR-screening of carbonyl compounds in metal working fluid aerosols by I. Trapp; T. Famulok; U. Risse; A. Kettrup (pp. 409-414).
Due to the complex composition of metal working fluids (MWF) the determination of all individual compounds is sometimes difficult and very expensive. Today the widely used method for the quantification of airborne MWFs consists of a non specific IR analysis of their C-H valence bands. With a new design of sample cell this inexpensive technique was extended to a more detailed screening of the MWF composition, especially the detection of carbonyl compounds in MWFs and their aerosols and vapors. The screening method was evaluated for the determination of concentrations of the aldehyde nonanal and the ketone diacetone alcohol in air in laboratory experiments. In preliminary workplace studies the applicability of this method to the (semi-)quantitative determination of carbonyl compounds in airborne MWFs is shown. The screening method was found to be very useful, specially to detect alterations in the composition of the MWF due to industrial use.
A PVC-based cryptand C2B22 membrane potentiometric sensor for zinc(II) by Hamid Reza Pouretedal; M. Shamsipur (pp. 415-418).
A PVC membrane electrode for zinc ions based on cryptand C2B22 as membrane carrier was prepared. The electrode exhibits a linear stable response over a wide concentration range (5.0 × 10–2– 5.0 × 10–5 mol/L) with a slope of 24 mV/ decade and a limit of detection of 3.98 × 10–5 mol/L (2.6 μg/g). It has a fast response time of about 30 s and can be used for at least 4 months without any divergence in potential. The proposed sensor revealed good selectivities for Zn2+ over a wide variety of other metal ions and could be used in a pH range of 4–7. It was used as an indicator electrode in potentiometric titration of zinc ion.
Determination of metal ions by capillary electrophoresis using pre-column complexation with 1,10-phenanthroline by F. Bedia Erim; Kezban Akın-Şenel (pp. 418-421).
The capillary electrophoretic separation of Fe(II), Cu(II) and Zn(II) ions in an acidic buffer solution (pH 2.5) by complexation with 1,10-phenanthroline is investigated. As 1,10-phenanthroline is a neutral ligand, the positively charged metal complexes formed migrate in the same direction as the EOF, providing a rapid separation of metal ions in acidic buffers. The method was applied to the determination of metal ions in vitamin tablets.
Cupferron separation for the determination of tantalum in high-purity iron and low alloy steel by ICP-AES by Yûetsu Danzaki; Kunio Takada; Kazuaki Wagatsuma (pp. 421-423).
For the determination of Ta (> 0.0005 mass %) in iron and low-alloy steel spectrophotometric methods, e.g., after the extraction of the Ta-Victoria Blue B complex by benzene, are generally used. To avoid the application of poisonous benzene as extracting solvent and to improve the detection power, an ICP-AES method after the separation of Ta by coprecipitation with cupferron has been developed. The detection limit (3σ) of 0.6 μgTa/g is lower in comparison with spectrophotometric methods. Therefore, the method also allows the determination of Ta-concentrations in the μg/g-range in high-purity iron.
Potentiometric back-titration of sulfate ion using a tetraphenylborate derivative as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode by T. Masadome; Yasukazu Asano (pp. 423-425).
A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium tetrakis (4-fluorophenyl) borate.
Determination of traces of metals in wines from Macedonia by L. Šoptrajanova; I. Spirevska; S. Petrovska-Jovanović; K. Stojanova (pp. 425-427).
A new method for the determination of chromium and manganese in wines using square-wave voltammetry was developed. For chromium, acrylic acid was chosen as supporting electrolyte and for manganese a mixture of NH4OH and NH4Cl. The experimental conditions (initial and final potential, frequency, pulse height, scan increment, scan rate and equilibrium and deposition time) were optimized. Chromium and manganese were determined in the Macedonian wines Kratošija, Kavadarka, Ohridija and Smederevka. The results agreed well with those obtained by standard UV/VIS spectrophotometry. A statistical treatment of the experimental data was performed using STATGRAPH and MATHCAD software packages.