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11.
《Electroanalysis》2004,16(9):748-756
A strategy for constructing a global multivariate calibration model that includes calibration samples measured over time on different days is developed and applied in electroanalysis. Both synthetic and real samples (tap, extracted and river water) are analyzed by differential‐pulse anodic stripping voltammetry, showing the suitability of the global model constructed that provides successful results similar to those of the usual multivariate calibration. In addition the capability of discrimination of this model is evaluated in prediction for the mean of three replicates with estimation of probability of false noncompliance, α, and false compliance, β, being found 3.1, 11.2, 6.7 and 64.7 nM for nominal concentrations of zinc, cadmium, lead and copper of 96.0, 40.4, 37.3 and 328.0 nM respectively when α=β=0.05. It has been proven that the use of the global calibration does not imply a loss of multivariate analytical sensitivity, using this parameter as quality index of the analytical procedure. The viability of using calibration maintenance strategies with electroanalytical techniques is shown, providing a way to save time and experimental effort when these techniques are used in routine analysis. 相似文献
12.
含三正辛胺微胶囊对六价铬的富集 总被引:5,自引:0,他引:5
本文将对六价铬有效的萃取剂TOA(三正辛胺)微胶囊化,制成填充柱型的酸性体系六价铬的富集分离装置。实验结果表明,微胶囊填充柱中每毫升TOA对六价铬的最大萃取容量为158.0g/mL,为纯TOA液相萃取的4.9倍。微胶囊经碱/水洗涤后,可再生使用。 相似文献
13.
A highly selective solid phase extraction sorbent for pre-concentration of sameridine made by molecular imprinting 总被引:5,自引:0,他引:5
Summary A novel approach to solid phase extraction, based on the use of a highly selective molecularly imprinted polymer, is presented.
The versatility of this type of sorbent for solid phase extraction was demonstrated in a model batch-wise pre-concentration
of sameridine prior to gas chromatography. Problems associated with leakage of remaining imprint molecules during the desorption
phase could be eliminated by the use of a close structural analogue of sameridine as the imprint species. It was found that
a major benefit of the imprinted polymer was its specificity, which lead to distinctly cleaner chromatographic traces and
ability to improve sensitivity by extracting sameridine from larger sample volumes. 相似文献
14.
15.
The stability of Ochratoxin A during its extraction using different extraction techniques has been evaluated. Microwave-assisted extraction and pressurised liquid extraction, in addition to two other reference methods of extraction, i.e. ultrasound-assisted and magnetic stirring-assisted extraction, were evaluated. The effect of extraction temperature using the cited techniques was checked.The results show that Ochratoxin A can be extracted using microwave-assisted extraction at temperatures up to 150 °C without degradation. Pressurised liquid extraction can be used at temperatures up to 100 °C, for extraction times of less than 30 min. Further, both ultrasound-assisted extraction and magnetic stirring extraction can be applied at temperatures up to 65 °C.High-performance liquid chromatography combined with fluorescence detection using a Chromolith RP-18e column at a flow rate of 5 mL min−1 was used to quantify the Ochratoxin A. The retention time for the Ochratoxin A was 1.3 min. The limits of detection (LOD) and of quantification (LOQ) were 0.03 and 0.10 μg L−1, respectively. 相似文献
16.
Optical properties of polarization-dependent geometric phase elements with partially polarized light
Yuri Gorodetski 《Optics Communications》2006,266(2):365-375
The behavior of geometric phase elements illuminated with partially polarized monochromatic beams is investigated both theoretically and experimentally. The element discussed in this paper is composed of wave plates with π-retardation and a space-variant orientation angle. We found that a beam emerging from such an element comprises two polarization orders; right-and left-handed circularly polarized states with conjugate geometric phase modification. This phase equals twice the orientation angle of the space-variant wave plate comprising the element. Apart from the two polarization orders, the emerging beam coherence polarization matrix includes a “vectorial interference matrix” which contains information concerning the correlation between the two orthogonal, circularly polarized portions of the incident beam. In this paper we measure this correlation by a simple interference experiment. In addition, we found that the equivalent mutual intensity of the emerging beam is modulated according to the geometric phase induced by the element. Other interesting phenomena concerning propagation will be discussed theoretically and demonstrated experimentally. The experiment made use of a spherical geometric phase element that was realized by use of a space-variant subwavelength grating illuminated with CO2 laser radiation of 10.6 μm wavelength. 相似文献
17.
Uptake of trace elements into fish otoliths is governed by several factors such as life histories and environment in addition to stock and species differences. In an attempt to elucidate the elemental signatures of rare earth elements (REEs) in otoliths, a solid phase extraction (SPE) protocol was used in combination with electrothermal vaporization (ETV) as a sample introduction procedure for the determinations by inductively coupled plasma quadrupole mass spectrometry (ICP-MS). Effects of various parameters, such as carrier gas flow rate, atomization temperature and chemical modification, were examined for optimization of the conditions by ETV-ICP-MS. Atomization was achieved at 2800 °C. Lower temperatures (i.e. 2600 °C) resulted in severe memory problems due to incomplete atomization. Palladium was used as a chemical modifier. It was found that an increase in Pd concentration up to 0.5 μg in the injection volume (70 μl) led up to four-fold enhancement in the integrated signals. This phenomenon is attributed to the carrier effect of Pd rather than the stabilization since no significant losses were observed for high temperature drying around 700 °C even in the absence of Pd. Preconcentration was performed on-line at pH 5 by using a mini-column of Toyopearl AF-Chelate 650M chelating resin, which also eliminated the calcium matrix of otolith solutions. After preconcentration of 6.4 ml of solution, the concentrate was collected in 0.65 ml of 0.5% (v/v) HNO3 in autosampler cups, and then analyzed by ETV-ICP-MS. The method was validated with the analysis of a fish otolith certified reference material (CRM) of emperor snapper, and then applied to samples. Results obtained from otoliths of fish captured in the same habitat indicated that otolith rare earth element concentrations are more dependent on environmental conditions of the habitat than on species differences. 相似文献
18.
To find an effective extraction and removal method for palladium(II), which is one of the main fission products from an acidic nuclear spent fuel solution, the extraction behavior of palladium(II) from a nitric acid medium by an acidic chelating extractant, 1-phenyl-3-methyl-4-trifluoroacetylpyrazolone-5-one (HPMTP) and a tertiary amine of high molecular weight, tri-n-octylamine (TOA), has been studied by spectrophotometry. A noticeable antagonistic extraction effect was observed in the extraction system under the given conditions. To understand this phenomenon, a preliminary investigation was performed to explain the mechanism of this reaction. According to the theory of corresponding solutions (TCS), the association reaction between HPMTP and TOA is proposed in the organic phase. An associated species, HPMTP·TOA, formed through hydrogen bonding in a chloroform medium might be the main reason why an antagonistic extraction effect occurred. The association constant between HPMTP and TOA was calculated to be 2.86±0.05. 相似文献
19.
Dmitry Dolgopyat 《Transactions of the American Mathematical Society》2004,356(4):1637-1689
We consider a large class of partially hyperbolic systems containing, among others, affine maps, frame flows on negatively curved manifolds, and mostly contracting diffeomorphisms. If the rate of mixing is sufficiently high, the system satisfies many classical limit theorems of probability theory.
20.
A new type of optoelectronic cellular neural network has been developed by providing the capability of coefficients adjusment of cellular neural network (CNN) using Widrow based perceptron learning algorithm. The new supervised cellular neural network is called Widrow-CNN. Despite the unsupervised CNN, the proposed learning algorithm allows to use the Widrow-CNN for various image processing applications easily. Also, the capability of CNN for image processing and feature extraction has been improved using basic joint transform correlation architecture. This hardware application presents high speed processing capability compared to digital applications. The optoelectronic Widrow-CNN has been tested for classic CNN feature extraction problems. It yields the best results even in case of hard feature extraction problems such as diagonal line detection and vertical line determination. 相似文献