A Duffing oscillator algorithm to detect the weak chromatographic signal

Based on the Duffing equation, a Duffing oscillator algorithm (DOA) to improve the signal-to-noise ratio (SNR) was presented. By simulated and experimental data sets, it was proven that the signal-to-noise ratio (SNR) of the weak signal could be greatly enhanced by this method. Using signal enhancement by DOA, this method extends the SNR of low concentrations of methylbenzene from 2.662 to 29.90 and the method can be used for quantitative analysis of methylbenzene, which are lower than detection limit of an analytical system. The Duffing oscillator algorithm (DOA) might be a promising tool to extend instrumental linear range and to improve the accuracy of trace analysis. The research enlarged the application scope of Duffing equation to chromatographic signal processing.     

A linear modulation-based stochastic resonance algorithm applied to the detection of weak chromatographic peaks

A simple stochastic resonance algorithm based on linear modulation was developed to amplify and detect weak chromatographic peaks. The output chromatographic peak is often distorted when using the traditional stochastic resonance algorithm due to the presence of high levels of noise. In the new algorithm, a linear modulated double-well potential is introduced to correct for the distortion of the output peak. Method parameter selection is convenient and intuitive for linear modulation. In order to achieve a better signal-to-noise ratio for the output signal, the performance of two-layer stochastic resonance was evaluated by comparing it with wavelet-based stochastic resonance. The proposed algorithm was applied to the quantitative analysis of dimethyl sulfide and the determination of chloramphenicol residues in milk, and the good linearity of the method demonstrated that it is an effective tool for detecting weak chromatographic peaks. Figure The linear modulation-based stochastic resonance algorithm (LSRA) improved the output chromatographic peak of chloramphenicol     

Stochastic resonance is applied to quantitative analysis for weak chromatographic signal of glyburide in plasma

Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml⁻¹, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml⁻¹ of glyburide in plasma and the method can be used for quantitative analysis of glyburide.     

A method based on stochastic resonance for the detection of weak analytical signal

An effective method for detection of weak analytical signals with strong noise background is proposed based on the theory of stochastic resonance (SR). Compared with the conventional SR-based algorithms, the proposed algorithm is simplified by changing only one parameter to realize the weak signal detection. Simulation studies revealed that the method performs well in detection of analytical signals in very high level of noise background and is suitable for detecting signals with the different noise level by changing the parameter. Applications of the method to experimental weak signals of X-ray diffraction and Raman spectrum are also investigated. It is found that reliable results can be obtained.     

Improved stochastic resonance algorithm for enhancement of signal-to-noise ratio of high-performance liquid chromatographic signal

Based on the theory of stochastic resonance, an improved stochastic resonance algorithm with a new criterion for optimizing system parameters to enhance signal-to-noise ratio (SNR) of HPLC/UV chromatographic signal for trace analysis was presented in this study. Compared with the conventional criterion in stochastic resonance, the proposed one can ensure satisfactory SNR as well as good peak shape of chromatographic peak in output signal. Application of the criterion to experimental weak signals of HPLC/UV was investigated and the results showed an excellent quantitative relationship between different concentrations and responses.     

Stochastic resonance algorithm applied to quantitative analysis for weak liquid chromatographic signal of pyrene in water samples

The phenomenon of stochastic resonance (SR), which was discovered in recent years, rendered an entirely new way for the detection of weak signals, and it has been widely studied in many different science fields. This phenomenon is manifest in nonlinear systems whereby a weak signal can be amplified when the noise, signal and nonlinear system attain the proper cooperation. The introduced algorithm was employed to detect pyrene in drinking water samples with solid-phase extraction–liquid chromatography. The weak chromatographic peak of the analyte was amplified significantly, and the profiles of the peaks were also satisfactory. The limit of detection and the limit of quantification were improved from 0.022?ng?mL^?1 and 0.08?ng?mL^?1 to 0.004?ng?mL^?1 and 0.01?ng?mL^?1, respectively. The results showed an excellent quantitative relationship between concentrations and chromatographic responses. It is expected that the SR will be an effective tool to detect weak chromatographic peaks quantitatively in trace analysis.     

The stochastic resonance algorithm with the direct current signal as external force and its application to the detection of weak chromatographic peaks

As a potential tool for amplifying weak chromatographic peaks, the stochastic resonance algorithm was developed based upon a counterintuitive physical phenomenon. Therefore, the essential step, parameter optimization, was perplexing and difficult for analysts. In order to avoid optimizing the system parameters on a case‐by‐case basis, an improved algorithm was proposed by introducing a constant or direct current signal into the signal to be measured as the external force. The weak chromatographic peak can be amplified and detected by the new algorithm using the same set of parameters. Two sets of our previous experimental data were reanalyzed by using the developed algorithm and the results were satisfactory. A generalized solution was expected to come into being on account of the new algorithm.     

一种有效提取微弱信号的新方法

根据小波变换能进行时频局部化分析的特性,本文提出一种用小波分段分析处理信号的方法。对任意长度的信号数据,在不增减信号点的情况下,提高分析信号的信噪比,有效地从信号中提取有用信息。将它应用于微弱信号检测,效果满意。     

一种有效提取弱信号的新方法

随机共振 ( Stochastic Resonance,简称 SR)最初由 Benzi[1] 于 1 981年提出 ,并在气象学领域中得到了成功的应用 .根据随机共振理论 ,通过加噪声可在某一“共振”点处大幅度提高信号的信噪比 .这种方法也已成功地应用于方波脉冲信号的恢复 [2 ] ,但在化学信号中的应用尚属空白 .我们首次将这种方法用于化学弱信号的检测 ,并在简单喇曼谱图的解析中获得成功 [3 ] .但是 ,加噪声的方法作为一种有效的信号分析手段还显得很不成熟 .具体表现为处理过程较繁 ,分析信号的峰位偏移明显 ,而且结果在一定程度上要依赖人为判断来决定 [3 ] .　　在…     

A Novel Approach to Improve the Detectability of CO2 by GC Analysis

A novel stochastic resonance algorithm was employed to enhance the signal-to-noise ratio (SNR) of signals of analytical chemistry.By using a gas chromatographic data set,it was proven that the SNR was greatly improved and the quantitative relationship between concentrations and chromatographic responses remined simultancously.The linear range was extended beyond the instrumental detection limit.     

A new way to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering signal and its potential application

A novel assay has been developed to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering (RLS) technique. The proposed method can be used to study those drugs which do not produce a RLS-signal after binding to DNA. RLS was used to monitor the interaction of five anticancer drugs with DNA. The reaction between anticancer drugs and DNA took place in BR buffer solution. From the RLS assay, the sequence of five anticancer drugs activities was as follows: CTX < MTX < Pt < MMC < 5-Fu. Mammary cancer cell DNA (mcDNA) was involved to validate the RLS assay. The results showed that the sensitivities of the five anticancer drugs targeting both mcDNA and ctDNA increased in the same order. However the sensitivity of each drug to mcDNA was higher than that to ctDNA It is a significant innovation of the RLS method to detect the interaction of DNA and anticancer drugs and to obtain drug sensitivity, which provides new strategies to screen DNA targeted anticancer drugs.     

基于周期调节的随机共振算法对化学弱信号的检测研究

提出了一种新的随机共振算法,通过对系统的周期进行调节以实现系统的共振.讨论了实现共振的系统参数,并对模拟信号和拉曼光谱实验信号进行了处理.结果表明,该方法不仅可方便地用于弱化学信号的处理,克服检出信号的滞后现象,而且对不同噪声水平的信号均有良好的适用性.     

Comparative investigation of irradiated meat by the methods of electron paramagnetic resonance and gas chromatography

A comparative study of irradiated pork meat containing bone was made by the methods of electron paramagnetic resonance (EPR) and gas chromatography (GC). In this investigation EPR has the advantage to be a very fast and unambiguous method even in the cases of thermal treatment of bones. On the other hand, GC analysis is a time consuming procedure however, it becomes very valuable for meat samples that contain no bones.     

强噪声背景中微弱信号检测的初步研究

为了提高信噪比,以往大都设法滤除噪声。根据随机共振理论,本文对用添加噪声来提高测量信号信噪比的方法进行了初步的尝试,并将此方法应用于强噪声背景中微弱信号的检测,得出了一些有意义的初步结构。     

A new signal processing method to observe weak P and O NMR peaks

In NMR spectroscopy, situations may arise where sample concentrations are below the threshold for FT NMR detection, or sample lability constrains allowable acquisition times. In ³¹P NMR, for example, observation of ¹³C satellites may not be practical under given conditions. For ¹⁷O NMR, which is useful to characterize ¹⁷O-labeled phosphate derivatives, similar considerations may apply, and added factors are the cost of isotopically enriched samples and the requirement to obtain spectra at relatively high temperatures if narrow spectral peak line widths are desired. We report here application of a new signal processing method [S.D. Kunikeev, H.S. Taylor, J. Phys. Chem. A 108, 2004 743] to observation of weak ³¹P and ¹⁷O NMR peaks.     

Application of the stochastic resonance algorithm to the simultaneous quantitative determination of multiple weak peaks of ultra-performance liquid chromatography coupled to time-of-flight mass spectrometry

The stochastic resonance algorithm (SRA) has been developed as a potential tool for amplifying and determining weak chromatographic peaks in recent years. However, the conventional SRA cannot be applied directly to ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS). The obstacle lies in the fact that the narrow peaks generated by UPLC contain high-frequency components which fall beyond the restrictions of the theory of stochastic resonance. Although there already exists an algorithm that allows a high-frequency weak signal to be detected, the sampling frequency of TOFMS is not fast enough to meet the requirement of the algorithm. Another problem is the depression of the weak peak of the compound with low concentration or weak detection response, which prevents the simultaneous determination of multi-component UPLC/TOFMS peaks. In order to lower the frequencies of the peaks, an interpolation and re-scaling frequency stochastic resonance (IRSR) is proposed, which re-scales the peak frequencies via linear interpolating sample points numerically. The re-scaled UPLC/TOFMS peaks could then be amplified significantly. By introducing an external energy field upon the UPLC/TOFMS signals, the method of energy gain was developed to simultaneously amplify and determine weak peaks from multi-components. Subsequently, a multi-component stochastic resonance algorithm was constructed for the simultaneous quantitative determination of multiple weak UPLC/TOFMS peaks based on the two methods. The optimization of parameters was discussed in detail with simulated data sets, and the applicability of the algorithm was evaluated by quantitative analysis of three alkaloids in human plasma using UPLC/TOFMS. The new algorithm behaved well in the improvement of signal-to-noise (S/N) compared to several normally used peak enhancement methods, including the Savitzky-Golay filter, Whittaker-Eilers smoother and matched filtration.     

A weak cation-exchange phase for the separation of biogenic amines by open tubular liquid chromatography

Summary The preparation and performance of a weak cation-exchange stationary phase for Open Tubular Liquid Chromatography (OT-LC) was investigated. The stationary phase was prepared in 5.4 μm I.D. fused silica capillaries byin situ photopolymerization of a mixture of silicon acrylate and acrylic acid. The influence of pH, counter ion concentration and organic modifier concentration of the mobile phase on the retention was studied with catecholamines as test solutes using LIF detection. Other biological amines like amino acids, small peptides and nucleic acid derivatives could be separated on this stationary phase as well. The kinetic performance of the stationary phase was studied with several cations and neutral solutes.     

Headspace solvent microextraction A new method applied to the preconcentration of 2-butoxyethanol from aqueous solutions into a single microdrop

A new procedure and experimental setup for the headspace solvent microextraction of volatile organic materials from aqueous sample solutions is described. The extraction occurs by suspending a 3-μl drop of the solvent from the tip of a microsyringe to the headspace of a stirred aqueous sample solution for a preset extraction time. The temperature of the microdrop and the bulk of sample solution should be kept constant at optimized values. The sample analyses were carried out by gas chromatography. The procedure was successfully applied to the extraction and determination of 2-butoxyethanol from content of some color samples used for painting the outer coverage of some machines such as coolers, refrigerator, cloths machine, etc. Parameters such as extraction time, nature of extraction solvent, size of microdrop, sample volume, stirring rate, ionic strength and pH of sample solution were studied and optimized, and the method performance was evaluated.     

Mapping the intramolecular signal propagation pathways in protein using Bayesian change point analysis of atomic motions

We propose to use change points of atomic positions in the molecular dynamics trajectory as indicators of the propagating signals in protein. We designate these changes as signals because they can propagate within the molecule in the form of “perturbation wave”, transmit energy or information between different parts of protein, and serve as allosteric signals. We found that change points can distinguish between thermal fluctuations of atoms (noise) and signals in a protein despite the differences in the motility of amino acid residues. Clustering of the spatially close residues that were experiencing change points close in time, allowed us to map pathways of signal propagation in a protein at the atomic level of resolution. We propose a potential mechanism for the origin of the signal and its propagation that relies on the autonomic coherence resonance in atomic fluctuations. According to this mechanism, random synchronization of fluctuations of neighboring atoms results in a resonance, which increases amplitude of vibration of these atoms. This increase can be transmitted to the atoms colliding with the resonant atoms, leading to the propagating signal. The wavelet-based coherence analysis of the inter-atomic distances between carbon-alpha atoms and surrounding atoms for the residue pairs that belong to the same communication pathway allowed us to find time periods with temporarily locked phases, confirming the occurrence of conditions for resonance. Analysis of the mapped pathways demonstrated that they form a network that connects different regions of the protein.