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ABSTRACT: A flow injection on-line preconcentration technique, combined with graphite furnace atomic absorption spectrometry for the determination of gold in ore samples has been presented. An alpha-amino pyridine resin (AP) was loaded onto a microcolumn as the preconcentration reagent and a solution of 90% acetone-5% HCl-5% H(2)O was used for the gold elution. The Scaled Simplex Method was employed to optimize the flow injection manifold. The selected factors were optimized by the simultaneous consideration of two responses, absorbance and column retention efficiency, with only 12 tests. A detection limit of 0.065 mug Au/l (3sigma) with a relative standard deviation of 4.3%, was achieved. Ore samples containing gold have been analysed successfully using the proposed method.
Talanta 09/1995; 42(8):1081-8. · 3.79 Impact Factor
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ABSTRACT: A flow injection on-line microcolumn method has been studied for the separation and preconcentration of noble metals, Pd, Pt and Ir, followed by flame AAS determination. An alpha-amino pyridine resin was used as preconcentration reagent. Non-noble metals studied could be eliminated by 2M HCl solution in the rinsing stage. A group-eluent for all Pd, Pt and Ir was studied. Separation of individual noble metals could also be accomplished using selective eluents. This approach can be used both for the separation and determination of Pd, Pt and Ir in samples. The sensitivities and the sample frequency have been improved. The method has been applied to certified samples.
Talanta 06/1995; 42(5):685-92. · 3.79 Impact Factor
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ABSTRACT: This paper describes a simple and economic way to construct a computerized potentiometric stripping analysis system for teaching and research purposes. Keywords (Audience): First-Year Undergraduate / General
10/1994;
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ABSTRACT: A reverse-phase extraction column method has been employed as an on-line preconcentration technique for trace gold analysis by flame atomic absorption spectrometry. Di(methylheptyl)methyl phosphonate (DMHMP) loaded onto a macroporous resin was used as the immobilized phase. A thiourea-HCl solution was found successful in eluting the gold. The experimental parameters were optimized by Simplex Optimization, with 17 tests needed to obtain optimal conditions. Sensitivities of 5.2 mug/l. and 2.3 mug/l., with sample frequencies of 45/hr and 48/hr, were obtained by using single and dual-columns respectively. The recoveries for mixed composition samples were 93-110%.
Talanta 05/1994; 41(4):565-71. · 3.79 Impact Factor
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ABSTRACT: A flow-injection method is described, in which phosphate standards are introduced into a reagent stream containing Cd(2+) ,resulting in the formation of Cd(3)(PO(4))(2). The associated reduction in free metal concentration is sensed by a cadmium-selective electrode. With the exception of major interference from iodide and moderate interference from bromide and thiocyanate, the system exhibits excellent response to phosphate and selectivity over several common anions in solutions buffered at pH 8.4. A maximum sampling rate of 160/hr is possible for phosphate standards in the concentration range 10(-1)-10(-1)M with a 10(-4)M Cd(2+) reagent stream at a total flow-rate (carrier and reagent stream combined) of 8.4 ml/min.
Talanta 08/1990; 37(7):683-7. · 3.79 Impact Factor
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ABSTRACT: A potentiometric flow-injection system is described, in which iodide in the concentration range 10(-6)-10(-1)M may be determined at rates of up to 360 samples/hr at a flow-rate of 17.8 ml/min. Iodine, after on-line reduction to iodide with 0.1M sodium metabisulphite, can also be determined, with a throughput of 60 samples/hr for 10(-5)-10(-3)M iodine. Analyses of two pharmaceutical preparations for iodide and iodine are reported, and the results are in reasonable agreement with titrimetric values.
Talanta 04/1990; 37(3):313-6. · 3.79 Impact Factor
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ABSTRACT: The incorporation of platinum disk microelectrodes of various radii (2.5-50 microns) in a well-jet flow cell offers reduced limits of detection for the determination of copper in urine by flow injection analysis compared with standard methods based on a conventional sized glassy carbon disk macroelectrode (radius 1.5 mm), in a thin-layer cell. The radius of the platinum disk microelectrode was found to be critical with respect to both the limit of detection and flow rate dependence. An optimal radius value of 28 microns was found with detection limits increasing with both larger and smaller electrode radii. In contrast, as theoretically expected, a diminished flow rate dependence was observed the smaller the radii of the platinum disk microelectrodes. Sample cleanup and preparation is conveniently achieved by the use of Sep-Pak cartridges and formation of a copper dithiocarbamate complex. The metal complex is easily oxidized at platinum disk microelectrodes in acetonitrile, which was the solvent used in the flow injection method of analysis.
Analytical Chemistry 02/1990; 62(1):27-31. · 5.86 Impact Factor
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ABSTRACT: Gas sensors based on a-Fe 2 O 3 (Al) have been studied experimentally and theoretically. Those with 9 mol% Al-added, sintered at 8508C, exhibit good gas sensing responses to CO and CH 4 . Well formed polycrystalline particles, essential to good gas sensing properties, are observed. XRD data show that the Al is dissolved into the material. The improvement in the gas sensing performance is attributed to the increase of the speci®c surface area caused by this aluminum addition. Variation of surface energy due to the Al-doped iron(III) oxide is modeled with two-and three-dimensional periodic structures. The results show that stronger relaxation leads to a stabilization of the surface in the case of Al addition compared to that without Al addition. Without relaxation, the non Al-added surface has a much lower surface energy than the Al-added surface. Although the energy difference between the relaxed surfaces is small, it indicates that the growth of Al-added iron oxide is less exothermic than that of pure iron oxide, which would explain the smaller particle size and hence the increased surface area observed after Al addition. # 2001 Elsevier Science B.V. All rights reserved.
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ABSTRACT: A flow injection on-line microcolumn method has been studied for the separation and preconcentration of noble metals, Pd, Pt and Ir, followed by flame AAS determination. An α-amino pyridine resin was used as preconcentration reagent. Non-noble metals studied could be eliminated by 2M HCl solution in the rinsing stage. A group-eluent for all Pd, Pt and Ir was studied. Separation of individual noble metals could also be accomplished using selective eluents. This approach can be used both for the separation and determination of Pd, Pt and Ir in samples. The sensitivities and the sample frequency have been improved. The method has been applied to certified samples.
Talanta.
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ABSTRACT: Four filtering functions, rectangular, triangular, exponential and decay exponential for Fourier filtering have been compared in this study of potentiometric stripping analysis (PSA) data. The filtering procedure involves treating the potential coordinate as mathematically equivalent to a time coordinate to transform data to the frequency domain. After Fourier transformation, each method yielded signal-to-noise enhancement over the original data in the order, decay exponential > triangular > exponential > rectangular. Apart from the filtering functions, two different filtering procedures, conventional and reflectance, have been compared in this study. Peak area measurement was unaffected by the reflectance procedure, while an undesirable increase in peak area was observed in the conventional procedure. A linear peak area-concentration relationship was retained in all cases. The resolution of overlapping potential peaks, using copper and bismuth peaks as the example, was most improved using the rectangular filtering function and worst using the decay exponential filtering function. This is completely opposite to the results obtained in signal-to-noise enhancement study. Thus, a compromise between ratio enhancement and peak distortion has to be made, as the latter is always a trade-off in signal processing. With the use of a personal computer (PC) and commercial data acquisition systems, the original saved data can be stored. Selection of a particular type of filtering function to optimise the analytical signal can be achieved by applying various functions to the original signal, until a desirable output is obtained.
Analytica Chimica Acta. 338(3):167-178.
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ABSTRACT: Four digital signal processing methods, moving average smoothing, polynomial smoothing, rectangular low pass filtering and exponential low pass filtering have been compared in this study of potentiometric stripping analysis (PSA) data. For the filtering methods, a new procedure is introduced based on treating the potential coordinate as mathematically equivalent to a time coordinate to transform data to the frequency domain. After Fourier transformation, each method has yielded signal-to-noise () improvement over the original data, for example exponential low pass filtering providing a 2.3 times enhancement. Peak area measurement was unaffected by the two smoothing methods, while an undesirable increase in peak area was observed in the two filtering methods. A linear peak area-concentration relationship was retained in all cases. The original peak height calibration is poorly correlated linearly, although the complex curve is reproducible. However, after digital signal processing, peak height as the measuring parameter gave a good linear relationship to concentration. The filtering approach which allows optimum filtering and best peak resolution was readily established. The resolution of overlapping potential peaks, using copper and bismuth peaks as the example, was best improved using the rectangular low pass filtering method.
Analytica Chimica Acta.
