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1.
《Electroanalysis》2004,16(18):1514-1520
The wavelet derivative was developed for resolving overlapped signals in electrochemical analysis. It has been shown that the wavelet derivative could be used as an effective tool in resolution enhancement of the electrochemical signals. Since signal‐to‐noise ratio (SNR) does not degrade significantly at high order derivatives, the wavelet derivative is much better than the conventional numerical derivative in resolving practical signals with low SNR, particularly in the case when the overlapped degree of complex is high and high order derivatives are required for the further resolution enhancement. In this article, applications of the wavelet derivative in the voltammetric determination of small mounts of substances in the presence of large mounts of potentially interfering species are presented, and the advantages of this technique are discussed as well. 相似文献
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A novel method based on continuous wavelet transform (CWT) using Haar wavelet function for approximate derivative calculation
of analytical signals is proposed and successfully used in processing the photoacoustic signal. An approximate nth derivative of an analytical signal can be obtained by applying n times of the wavelet transform to the signal. The results obtained from four other different methods – the conventional numerical
differentiation, the Fourier transform method, the Savitzky-Golay method, and the discrete wavelet transform (DWT) method
– were compared with the proposed CWT method; it was demonstrated that all the results are almost the same for signals without
noise, but the proposed CWT method is superior to the former four methods for noisy signals. The approximate first and second
derivative of the photoacoustic spectrum of Pr(Gly)3Cl3· 3 H2O and PrCl3· 6 H2O were obtained using the proposed CWT method; the results are satisfactory.
Received: 21 December 1999 / Revised: 28 February 2000 / Accepted: 7 March 2000 相似文献
4.
Zorana Grabari Boidar S. Grabari Miquel Esteban Enric Casassas 《Journal of Electroanalytical Chemistry》1997,420(1-2)
Ratio differential pulse polarograms obtained by dividing the multianalyte and single analyte signals are proposed as a tool for resolution of global signals and quantification of the analytes from a qualitatively known mixture by differential pulse polarography (DPP) and related electroanalytical techniques. The influences of shape and position of the resolving function (DP polarograms of individual analyte) on the efficiency of resolution are discussed on simulated and experimental results. The method is applied for the determination of p-nitroaniline (NA) and p-nitrotoluene (NT) from their mixture in N,N′-dimethylformamide solutions with 0.1 M tetrabutylammonium iodide as supporting electrolyte, using an external calibration diagram and internal standard addition methods. NA and NT give one-electron DP polarographic peaks with 93 mV of peak separation and, therefore, show significant overlapping which depends on the concentration ratio of NA and NT in the mixture. The method is especially suitable for quantification of one analyte in the presence of a large excess of another analyte, because by division the component in excess is removed and the pseudo-ratio DPP of the minor component is clearly revealed in a way which is not possible by deconvolution using polynomial division or deconvolution by Fourier transforms. 相似文献
5.
Foca G Ferrari C Sinelli N Mariotti M Lucisano M Caramanico R Ulrici A 《Analytical and bioanalytical chemistry》2011,399(6):1965-1973
Spectral resolution (R) and number of repeated scans (S) have a significant effect on the S/N ratio of Fourier transform-near infrared (FT-NIR) spectra, but the optimal values of these two parameters have to be determined
empirically for a specific problem, considering separately both the nature of the analysed matrix and the specific instrumental
setup. To achieve this aim, the instrumental noise of replicated FT-NIR spectra of wheat samples was modelled as a function
of R and S by means of the Doehlert design. The noise amounts in correspondence to different experimental conditions were
estimated by analysing the variance signals derived from replicate measurements with two different signal processing tools,
Savitzky–Golay (SG) filtering and fast wavelet transform (FWT), in order to separate the “pure” instrumental noise from other
variability sources, which are essentially connected to sample inhomogeneity. Results confirmed that R and S values leading to minimum instrumental noise can vary considerably depending on the type of analysed food matrix and on the
different instrumental setups, and helped in the selection of the optimal measuring conditions for the subsequent acquisition
of a wide spectral dataset. 相似文献
6.
The normal distribution function is used as resolving factor and spline wavelet self‐convolution is used to resolve the overlapped peaks containing noise. The resolution of several kinds of overlapped peaks (SNR from 5 to 50) simulated by computer has been discussed in details. It is known that the overlapped peaks with noise can be separated (SNR > 50) directly and the noise is removed at the same time in time domain. Base‐line separation can be achieved. The relative errors of peak area and position are less than 5.0%. The satisfactory results are also obtained in resolving voltammetric overlapped signals by this method. 相似文献
7.
A novel method to calculate the approximate derivative photoacoustic spectrum using continuous wavelet transform 总被引:1,自引:0,他引:1
A novel method based on continuous wavelet transform (CWT) using Haar wavelet function for approximate derivative calculation of analytical signals is proposed and successfully used in processing the photoacoustic signal. An approximate nth derivative of an analytical signal can be obtained by applying n times of the wavelet transform to the signal. The results obtained from four other different methods--the conventional numerical differentiation, the Fourier transform method, the Savitzky-Golay method, and the discrete wavelet transform (DWT) method--were compared with the proposed CWT method; it was demonstrated that all the results are almost the same for signals without noise, but the proposed CWT method is superior to the former four methods for noisy signals. The approximate first and second derivative of the photoacoustic spectrum of Pr(Gly)3Cl3.3H2O and PrCl3.6H2O were obtained using the proposed CWT method; the results are satisfactory. 相似文献
8.
以地阶跃伏安法中干扰信号的消除提出了一种新方法,即将条小波和RLT滤波技术相结合既可以滤去随机噪声,又可以滤去充充电电流。方法效果较好。 相似文献
9.
De-noising signals is a frequent aim achieved by signal processing in analytical chemistry. The purpose is to enable the detection
of trace concentrations of analytes. The limit of detection is defined as the lowest amount of analyte that still causes signals
greater than the background noise. Appropriate de-noising decreases only the noise and maintains the measurement signal, so
that signal-to-noise ratios are enhanced. One adequate mean of signal processing for this purpose is wavelet transform, which
still is not a common tool in analytical chemistry. In this paper, the ability of de-noising by wavelet transform is shown
for measurements in anodic stripping voltammetry using a hanging mercury drop electrode. The calculation of limits of detection
and signal-to-noise ratios on the basis of peak-to-peak noise is exercised to quantify the performance of de-noising. Furthermore,
signal shape with regard of easing the application of base lines is discussed. Different wavelet functions are used, and the
results are compared also to Fourier transform. Coiflet2 was found out to reduce noise by the factor of 330 and is proposed
as the adequate wavelet function for voltammetric and similar signals. 相似文献
10.
Fourier self-deconvolution is an effective means of resolving overlapped bands, but this method requires a mathematical model to yield deconvolution and it is quite sensitive to noises in unresolved bands. Wavelet transform is a technique for noise reduction and deterministic feature capturing because its time-frequency localization or scale is not the same in the entire time-frequency domain. In this work, wavelet transform-based Fourier deconvolution was proposed, in which a discrete approximation (such as A(2)) obtained from performing wavelet transform on the original data was substituted for the original data to be deconvolved and another discrete appropriate approximation (such as A(5)) was used as a lineshape function to yield deconvolution. Again, instead of the apodization function, the B-spline wavelet was used to smooth the deconvolved data to enhance the signal-to-noise ratio. As a consequence, this method does not suffer as badly as Fourier self-deconvolution from noises in the original data. Thus, resolution enhancement can be increased significantly, especially for signals with higher noise level. Furthermore, this method does not require a mathematical model to yield deconvolution; it is very convenient to deconvolve electrochemical signals. 相似文献
11.
小波包分析用于重叠分析化学信号的处理 总被引:9,自引:1,他引:8
对小波包分析的算法进行了改进,并将此算法成功地应用于多组分重叠色谱信号的解析.结果表明,本文提出的算法解决了MRSD算法的不足,更适合处理分析化学信号,用于重叠信号的解析时不需重构(逆变换),简化了数据处理步骤,加快了数据解析速度,具有较强的解析能力.对于重叠色谱信号的解析,小波包分析比小波分析具有更强的解析能力. 相似文献
12.
A novel method named a wavelet packet transform based Elman recurrent neural network (WPTERNN) was proposed for the simultaneous
UV–visible spectrometric determination of Cu(II), Cd(II) and Zn(II). This method combined wavelet packet denoising with an
Elman recurrent neural network. A wavelet packet transform was applied to perform data compression, to extract relevant information,
and to eliminate noise and collinearity. An Elman recurrent network was applied for nonlinear multivariate calibration. In
this case, using trials, the kind of wavelet function, the decomposition level, and the number of hidden nodes for the WPTERNN
method were selected as Daubechies 14, 3, and 8, respectively. A program (PWPTERNN) was designed that could perform the simultaneous
determination of Cu(II), Cd(II) and Zn(II). The relative standard errors of prediction (RSEP) obtained for all components
using WPTERNN, a Elman recurrent neural network (ERNN), partial least squares (PLS), principal component regression (PCR),
Fourier transform based PCR (FTPCR), and multivariate linear regression (MLR) were compared. Experimental results demonstrated
that the WPTERRN method was successful even where there was severe overlap of spectra. The results obtained from an additional
test case also demonstrated that the WPTERNN method performed very well.
Figure The part of WP coefficients obtained by wavelet packet transforms 相似文献
13.
Some mathematical methods for the elimination of noise in stripping voltammetric curves are compared. On the basis of the obtained data, the wavelet transform method is proposed for noise filtering. 相似文献
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二维小波变换与子窗口因子分析法结合用于含噪声HPLC-DAD数据的解析 总被引:1,自引:0,他引:1
将二维小波变换与子窗口因子分析法相结合,用于模拟的高噪声HPLC-DAD数据的解析.首先应用二维小波变换滤除噪声,然后采用子窗口因子分析法解析重叠峰.结果表明,信噪比为10的高噪声基本被滤除掉. 相似文献
16.
A Background and noise elimination method for quantitative calibration of near infrared spectra 总被引:1,自引:0,他引:1
Da Chen 《Analytica chimica acta》2004,511(1):37-45
A new hybrid algorithm is proposed to eliminate the varying background and noise simultaneously for multivariate calibration of near infrared (NIR) spectral signals. The method is based on the use of multi-resolution, which is one of the main advantages provided by wavelet transform. The signals are firstly split into different frequency components, which keep the same data points of the original signals. In conjunction with a modified uninformative variable elimination (mUVE) criterion, the new method can be used to remove the low-frequency varying background and the high-frequency noise simultaneously. The method is successfully applied to simulated spectral data set and experimental NIR spectral data, resulting in more parsimonious multivariate models with higher precision. In addition, the proposed strategy can be applied to other spectral signals as well. 相似文献
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In this paper, a new signal-processing procedure is applied to the optimization of voltammetric determination of antimony in the presence of copper and the parallel determination of these two elements. The proposed numerical algorithm for the separation of the overlapping peaks utilizes the continuous wavelet transform and the inverse continuous wavelet transform. As the base function, the specially defined dedicated mother wavelet is used. In its construction the ideal, simulated voltammetric peak is intensively exploited. This approach, corresponding to the wavelet theory, gives satisfactory signals separation, even in the cases when they constitute one peak. The possibility of Sb(III) determination is presented in the case of different distances between copper and antimony peaks and also in 10-, 20- and 50-fold excesses of Cu. The parallel determination of Cu(II) and Sb(III) is possible even in the case of a 10-fold excess of copper. The quality of the obtained results fulfills the requirements of validation. 相似文献
19.
《Analytical letters》2012,45(12):2507-2520
ABSTRACT A novel algorithm of wavelet transform, called the on-line wavelet transform, which can be used in on-line processing of signals of an instrumental analysis, is proposed. And application of the on-line wavelet transform in denoising of high performance liquid chromatograms was investigated. Results showed that the noise in chromatograms was cleanly removed by the method, peak position after the on-line de-noising dose not change, and the linearity of calibration curves of concentration versus peak area remained and even was improved. Quantitative determination of three mixed samples were investigated with five standard samples; the recoveries were between 94.0-105.0%. 相似文献
20.
A new graphical method based on the one-dimensional wavelet transform (WT) was proposed and tested on mixture of thiamine hydrochloride (THI) and pyridoxine hydrochloride (PYR) in the presence of strongly overlapping signals. We selected from the data of the UV-VIS absorption spectra a signal consisting of 1150 points corresponding to the concentration range 8-32 mg ml−1 for each vitamin and we subjected it to Daubechies8 (DAUB8) and Biorthogonal6.8 (BIOR6.8) wavelet transforms. Since the peaks of the transformed signals were bigger than original ones a zero crossing method was applied to obtain the calibration graphs. In addition, the validity of Beer-Lambert law was assumed for the transformed signals. An appropriate scale setting was choosing to obtain an alternative calibration for each method. Matlab 6.5 software was used for one-dimensional wavelet analysis and the basic concepts about wavelet method were given. The obtained results were successfully compared among each other as well as with those obtained by other literature methods. The method developed in this paper is rapid, easy to apply, not expensive and it is suitable for analyzing of the overlapping signals of compounds in their mixtures without any chemical pre-treatment. 相似文献