[Multivariate Calibration Combined with Mass Spectrometry for Rapid Analysis].

A mixture of four substances of benzaldehyde, iso-octane, butyl acetate, acetophenone were quantitatively analyzed by mass spectrometry combined with chemometrics. The mass chromatogram data of mixture were proceeded with two methods for quantitative analysis. One is feature selection--Multiple Linear Regression (MLR) and the other is full spectrum--Partial Least Squares (PLS). The results show that the RMSEP of benzaldehyde were 0.062 and 0.091 after selecting m/z spectrum and full spectrum respectively; RMSEP of isooctane were 0.048 and 0.057 after selecting spectrum and full spectrum respectively; which of butyl acetate were 0.021 and 0.020 and of acetophenone were 0.010 and 0.032. The feature selection results of the mixture were better than that of the full spectrum modeling results expect butyl acetate which got similar results by the two methods.

[Determination of calcium and magnesium in tobacco by near-infrared spectroscopy and least squares-support vector machine].

The purpose of the present paper is to determine calcium and magnesium in tobacco using NIR combined with least squares-support vector machine (LS-SVM). Five hundred ground and dried tobacco samples from Qujing city, Yunnan province, China, were surveyed by a MATRIX-I spectrometer (Bruker Optics, Bremen, Germany). At the beginning of data processing, outliers of samples were eliminated for stability of the model. The rest 487 samples were divided into several calibration sets and validation sets according to a hybrid modeling strategy. Monte-Carlo cross validation was used to choose the best spectral preprocess method from multiplicative scatter correction (MSC), standard normal variate transformation (SNV), S-G smoothing, 1st derivative, etc., and their combinations. To optimize parameters of LS-SVM model, the multilayer grid search and 10-fold cross validation were applied. The final LS-SVM models with the optimizing parameters were trained by the calibration set and accessed by 287 validation samples picked by Kennard-Stone method. For the quantitative model of calcium in tobacco, Savitzky-Golay FIR smoothing with frame size 21 showed the best performance. The regularization parameter λ of LS-SVM was e16.11, while the bandwidth of the RBF kernel σ2 was e8.42. The determination coefficient for prediction (Rc(2)) was 0.9755 and the determination coefficient for prediction (Rp(2)) was 0.9422, better than the performance of PLS model (Rc(2)=0.9593, Rp(2)=0.9344). For the quantitative analysis of magnesium, SNV made the regression model more precise than other preprocess. The optimized λ was e15.25 and σ2 was e6.32. Rc(2) and Rp(2) were 0.9961 and 0.9301, respectively, better than PLS model (Rc(2)=0.9716, Rp(2)=0.8924). After modeling, the whole progress of NIR scan and data analysis for one sample was within tens of seconds. The overall results show that NIR spectroscopy combined with LS-SVM can be efficiently utilized for rapid and accurate analysis of calcium and magnesium in tobacco.

[Simultaneous determination of instant coffee, plant fat and sugar content in liquid coffee beverage by diffuse reflectance near-infrared spectroscopy].

The diffuse reflectance near-infrared spectra of 20 liquid coffee beverage samples were collected by FT-NIR spectrometer combined with integral sphere in this thesis. The quantitative calibration models of instant coffee, plant fat and sugar were developed respectively. The result indicated that for the calibration models of instant coffee, plant fat and sugar, the dimensions of the calibration models are 4, 5 and 4 respectively; the determination coefficients (R2) are 98.97%, 99.94% and 99.18% respectively; the root mean square errors of calibration (RMSEC) are 1.62, 0.42 and 1.58 respectively; the root mean square errors of cross validation (RMSECV) are 2.12, 0.72 and 2.01 respectively. The result of F-test showed that a very remarkable correlation exists between the estimated and specified values for each calibration model. This research indicated that NIR spectroscopy can be applied in the rapid, accurate and simultaneous determination of the three main ingredients in liquid coffee beverage. This research can provide some references for the quality control of liquid coffee beverage and the determination of the substance with chemical-fixation composition in liquid formula food.

[UV spectroscopy coupled with partial least squares to determine the enantiomeric composition in chiral drugs].

In the present study, sucrose was used as a chiral selector to detect the molar fraction of R-metalaxyl and S-ibuprofen due to the UV spectral difference caused by the interaction of the R- and S-isomer with sucrose. The quantitative model of the molar fraction of R-metalaxyl was established by partial least squares (PLS) regression and the robustness of the models was evaluated by 6 independent validation samples. The determination coefficient R2 and the standard error of calibration set (SEC) was 99.98% and 0.003 respectively. The correlation coefficient of estimated value and specified value, the standard error and the relative standard deviation (RSD) of the independent validation samples was 0.999 8, 0.000 4 and 0.054% respectively. The quantitative models of the molar fraction of S-ibuprofen were established by PLS and the robustness of models was evaluated. The determination coefficient R2 and the standard error of calibration set (SEC) was 99.82% and 0.007 respectively. The correlation coefficient of estimated value and specified value of the independent validation samples was 0.998 1. The standard error of prediction (SEP) was 0.002 and the relative standard deviation (RSD) was 0.2%. The result demonstrates that sucrose is an ideal chiral selector for building a stable regression model to determine the enantiomeric composition.

[Near-infrared spectroscopy quantitative analysis model based on inverse regression].

In the present paper, an inverse regression method is used in near infrared (NIR) spectroscopy analysis to reduce dimension of predictor at first, then estimate linear regression function using the new derived low dimensional data. A real data set of 103 corn samples was used for analysis with this new inverse regression method. Taking 103 corn samples as experiment materials, seventy samples were chosen randomly to establish predicting model, the remaining thirty-three corn samples were viewed as prediction set. The new derived model is used to the prediction set. The coefficient is 0.986 and the average relative error is 2.1% between the model predication results and Kjeldahl's value for the protein content, and the resulis of using partial least square regression are 0.978 and 2.5%, respectively. The results demonstrate that the inverse regression method is feasible and has good property in near-infrared spectroscopy quantitative analysis, and also provides a new idea for chemometrics quantitative analysis.

[Rapid detection of dichlorvos in chlorpyrifos by mid-infrared and near-infrared spectroscopy].

In the present study, the content of dichlorvos in chlorpyrifos was rapidly determined by mid-infrared and near-infrared spectroscopy. The quantitative models were established by partial least squares (PLS) method and optimized. The independent validation sets and 7 test samples were used to evaluate the model accuracy. The results showed that mid-infrared and near-infrared spectroscopy can accurately determine the content of dichlorvos in chlorpyrifos. The RMSEC (the root mean square error of calibration) of the mid-infrared model and near-infrared model was 0.013 and 0.020, respectively. R2 (determination coefficient) both were 1.000. For 7 test samples, RMSEP before model recalibration is 0.22 (MIRS) and 0.09 (NIRS). The adaptability of the near-infrared model was much better and model updating was unnecessary. To sum up, MIR and NIR are both rapid and easy-operation method with simple pretreatment.

[Study on rapid determination of active ingredient of agrochemicals by near-infrared spectroscopy].

The main problem of disqualification of the agrochemicals is the insufficiency and abuse of its active ingredient, but lacking of the rapid and on the site analysis method. In the present thesis, the content of haloxyfop-r-methyl in the emulsifiable concentration was analyzed quantitatively by the FT-NIR spectroscopy combined with partial least square (PLS) method. The calibration models of haloxyfop-r-methyl were developed, the determination coefficients (R2) of the calibration models were no less than 0.999 9, the SEC were less than 0.019, and the SEP were less than 0.030. Meanwhile, the factors affecting the calibration model were studied and the validation was done by the actual sample. The result indicated that the method of near-infrared spectroscopy can predict the content of the active ingredient in emulsifiable concentration accurately; while the resolution of the instrument and the content of addition agent will not affect the prediction precision of the calibration model remarkably. Therefore, it is a feasible, convenient and quick method to analyze the active ingredient in the commodity agrochemicals by near-infrared spectroscopy, which has an important significance in the on-line determination, analysis on site in the enterprise and the rapid quantitative analysis of agrichemicals in the department of quality monitoring.

[Quantitative analysis of the content of deltamethrin in agrochemicals by near-infrared, attenuated total reflectance infrared and raman spectroscopy].

The method of near-infrared, attenuated total reflectance infrared and Raman spectroscopy was used for the rapid determination of the content of deltamethrin in agrochemicals. The quantitative models were established by PLS (partial least squares) method and optimized. The independent validation sets were used to evaluate the model accuracy. The determination coefficient R2 and RMSECV of the near-infrared model and mid-infrared model were 0.9999, 0.022 and 0.9996 and 0.056, respectively. The accuracy of both was similar. The determination coefficient R2 and RMSECV of Raman were 0. 996 7 and 0.172, which exhibits the lower accuracy. The result indicated that near-infrared, mid-infrared and Raman spectroscopy can be applied to the rapid determination of the content of the active ingredients precisely, which has an important significance in the on-line determination, analysis on site in the enterprise and the rapid quantitative analysis of agrichemicals in the department of quality monitoring.

[Near-infrared spectrum quantitative analysis model based on principal components selected by elastic net].

Elastic net is an improvement of the least-squares method by introducing in L1 and L2 penalties, and it has the advantages of the variable selection. The quantitative analysis model build by Elastic net can improve the prediction accuracy. Using 89 wheat samples as the experiment material, the spectrum principal components of the samples were selected by Elastic net. The analysis model was established for the near-infrared spectrum and the wheat's protein content, and the feasibility of using Elastic net to establish the quantitative analysis model was confirmed. In experiment, the 89 wheat samples were randomly divided into two groups, with 60 samples being the model set and 29 samples being the prediction set. The 60 samples were used to build analysis model to predict the protein contents of the 29 samples, and correlation coefficient (R) of the predicted value and chemistry observed value was 0. 984 9, with the mean relative error being 2.48%. To further investigate the feasibility and stability of the model, the 89 samples were randomly selected five times, with 60 samples to be model set and 29 samples to be prediction set. The five groups of principal components which were selected by Elastic net for building model were basically consistent, and compared with the PCR and PLS method, the model prediction accuracies were all better than PCR and similar with PLS. In view of the fact that Elastic net can realize the variable selection and the model has good prediction, it was shown that Elastic net is suitable method for building chemometrics quantitative analysis model.

[Fast determination of the proportion of metalaxyl-M enantiomers by UV spectroscopy].

In the present study, beta-cyclodextrin(betaCD) was used as chiral selector to detect the proportion of chiral isomers of metalaxyl. The proportion of metalaxyl enantiomers can be detected by ultraviolet (UV)spectroscopy since the interaction between the R, S isomer of metalaxyl with beta-CD is different. The quantitative models were established by partial least squares regression (PLS) and the robust of models was evaluated by independent validation samples. The determination coefficient R2 of calibration set in the quantitative model was 0.999 0. The standard error of calibration set (SEC) and the relative standard deviation (RSD) of the model was respectively 0.006 7 and 0.89%; The correlation coefficient r of estimated value and specified value of the 6 independent validation samples was 0.998 5. The standard error of prediction (SEP) and RSD was respectively 0.008 9 and 1.17%. This method is rapid and easy to operate in practical applications.

[Spectrofluorimetric study of supramolecular inclusion between rodenticide brodifacoum and beta-cyclodextrin and application].

The supramolecular interaction between beta-cyclodextrin and brodifacoum, an anticoagulant rodenticide of the second generation, was studied by spectroscopy. The results showed that brodifacoum and beta-cyclodextrin could form an inclusion complex with an association constant of 1.048 x 10(4) L x mol(-1) and a 1 : 1 stoichiometry based on Benesi-Hildebrand equation. The inclusion mechanism was proposed to explain the inclusion mode. It was indicated that the hydrophobic group of brodifacoum molecule, biphenyl, entered into the cavity of beta-cyclodextrin. At the same time, it was also observed the significant enhancement of fluorescence of brodifacoum after forming inclusion complex. According to the fluorescence enhancement phenomenon, a spectrofluorimetric method of detecting brodifacoum in aqueous media was established with the linear range of 8.0 x 10(-8)-4.0 x 10(-6) mol x L(-1) and the correlation coefficient of 0.999 4. The detection limit of the method was 8.8 x 10(-9) mol x L(-1). The proposed method was successfully applied to determine the trace amount of brodifacoum in environment water and the recovery was in the range of 87.3% to 103.9%.

[Study of the interaction mechanism between brodifacoum and DNA by spectroscopy].

The interaction between brodifacoum (3-[3-(4'-bromophenyl-4) 1,2,3,4-tetralin-10]-4-hydroxyl-coumarin) (BDF), an anticoagulant rodenticide, and calf thymus DNA (ct-DNA) was studied by UV spectrum and fluorescence spectrum. The results were summarized as follows: There was a hypochromic effect of low concentration ct-DNA on the UV spectra. The fluorescence quenching studies showed a regular decrease in the fluorescence intensity after addition of ct-DNA by the static quenching mode with a quenching constant (Ksv) of 1.21 x 10(4) L x mol(-1) at 27 degrees C. The BDF possibly bonded to ct-DNA mainly via Van der Waals forces by the corresponding thermodynamics parameter. KI quenching experiment found that there was not obvious protection of ct-DNA to BDF. The fluorescence intensity of BDF/ct-DNA system changed with the variation in ionic strength Quenching of ct-DNA on the fluorescence of BDF/beta-CD inclusion complex was reduced in contrast with the free BDF, which showed that beta-CD could provide BDF with protection. So the comprehensive interaction mode of BDF with ct-DNA may be the groove binding by the above results. It was indicated that there had been static-electro interaction between BDF and ct-DNA at the same time. The conjunct action of Van der Waals forces and electrostatic attraction favorably provide BDF bonding interaction in the groove of ct-DNA.

[Spectroscopic study on interaction of rodenticide brodifacoum with bovine serum albumin].

The mutual interaction of bovine serum albumin (BSA) with brodifacoum (3-[3-(4'-bromophenyl-4) 1,2,3,4-tetralin-10]-4-hydroxyl-coumarin), an anticoagulant rodenticide, was investigated by ultra-violet spectroscopy, flurorescence spectroscopy and synchronous fluorescence spectroscopy under physiological conditions. It was proved that the intrinsic fluorescence quenching of BSA by brodifacoum was the result of the formation of brodifacoum-BSA complex. And this quenching is mainly due to static fluorescence quenching. The quenching rate constant (K(sv)), binding site number (n) and binding constant (KA) at different temperatures were calculated from the double reciprocal Lineweaver-Burk plots and the quenching function of lg[(F0 - F)/F] - lg[Q] plots. The thermodynamic parameters indicated that the process of binding was a spontaneous molecular interaction and the hydrophobic force played a major role in stabilizing the brodifacoum BSA complex. The binding distance r between brodifacoum and BSA was 2.84 and 2.87 nm at 20 and 30 degrees C, respectively, which was obtained based on Forster theory of non-radiation energy transfer. The synchronous spectroscopy of BSA and brodifacoum-BSA revealed that the BSA conformation had changed in the presence of brodifacoum. The binding mode and interaction mechanism were suggested as follows: brodifacoum molecules are closed with amino acid residues with electric charge on the hydrophobic cavities of BSA by electrostatic interaction, and binded to the Trp212 residues inside of BSA hydrophobic cavities by hydrophobic interaction force, thereby changed the microenvironment around the Trp residues. The interaction prevented the energy transfer between Tyr and Trp residues, moreover, caused to a non-radiation energy transfer from Trp residues in BSA to brodifacoum, and finally leaded of the quenching the intrinsic fluorescence of BSA.

[Comparison of the models of mixed liquid samples under different near-infrared spectral resolutions].

Models of near-infrared spectra under different resolutions, 1, 4, 16, 32 and 64 cm(-1), were studied with the mixed liquid samples of 4 components. The calibration models were developed by the method of partial least square and the validations of the models were carried out by the method of full cross. The value of target function was used to estimate the models performance. For the calibration models developed by the raw spectra, the target function values of benzene and benzaldehyde reached the max value with the resolution of 1 cm(-1), the target function value of toluene reached the max value with the resolution of 4 cm(-1), and the target function value of chlorobenzene reached the max value with the resolution of 16 cm(-1); for calibration models developed by the 1st derivative spectra, the target function values of the four components all reached the max value with the resolution of 1 cm(-1). The result suggested that, first of all, the resolution of the instrument will influence the quantitative analysis result. For the component with spectrum overlapped seriously, a higher resolution is good for the quantitative analysis, while for the analyte with a broad real band width, a lower resolution can be adopted in order to assure the signal to noise ratio. In addition, the influence of the resolution of the instrument is different for different components. Furthermore, the quantitative analysis result can be affected by both the SNR of the raw spectra and the band width of different components in the analyte, and a higher resolution is good for the quantitative model when the SNR of the spectra is assured.

[Applications of near-infrared spectroscopy to analysis of traditional Chinese herbal medicine].

Analysis of traditional Chinese herbal medicine is of great importance to its quality control Conventional analysis methods can not meet the requirement of rapid and on-line analysis because of complex process more experiences or needed. In recent years, near-infrared spectroscopy technique has been used for rapid determination of active components, on-line quality control, identification of counterfeit and discrimination of geographical origins of herbal medicines and so on, due to its advantages of simple pretreatment, high efficiency, convenience to use solid diffuse reflection spectroscopy and fiber. In the present paper, the principles and methods of near-infrared spectroscopy technique are introduced concisely. Especially, the applications of this technique in quantitative analysis and qualitative analysis of traditional Chinese herbal medicine are reviewed.

[Study on the interaction of carbaryl and ctDNA by resonance light scattering spectra and its application].

Interaction modes of carbaryl and DNA were studied by resonance light scattering (RLS) spectra and absorption spectra. Experiments show that at pH 1.97, there are two interaction modes between carbaryl and ctDNA, namely surface assembly mode and intercalative mode. Interaction mode has a relation with the concentration ratio of carbaryl to ctDNA. Under this condition, the RLS intensity o f carbaryl and ctDNA is proportional to the concentration of ctDNA. According to this, one new simple and rapid method of determining ctDNA was set up. The linear ranges of the concentration of ctDNA were 0.02-3 microg x mL(-1), the linear regression equation was I = 200.77c (microg x mL(-1)) + 118.91, and the correlation coefficient was r = 0.998 9. This method has successfully been used to determine the synthetic samples.

Rapid qualitative and quantitative analysis of methamphetamine, ketamine, heroin, and cocaine by near-infrared spectroscopy.

Rapid and nondestructive near infrared spectroscopy (NIR) methods have been developed for simultaneous qualitative and quantitative analysis of methamphetamine, ketamine, heroin, and cocaine in seized samples. This is the first systematic report regarding a qualitative and quantitative procedure of applying NIR for drug analysis. A total of 282 calibration samples and 836 prediction samples were used for the building and validating of qualitative and quantitative models. Two qualitative analysis modeling methods for soft independent modeling by class analogy (SIMCA) and supporting vector machine (SVM) were compared. From its excellent performance in rejecting false positive results, SIMCA was chosen. The drug concentrations in the calibration and validation sample sets were analyzed using high-performance liquid chromatography. Based on the use of first-order derivative spectral data after standard normal variate (SNV) transformation correction, in the wavelength range from 10,000 to 4000cm-1, four partial least squares quantitative-analysis models were built. The coefficients of determination for all calibration models were >99.3, and the RMSEC, RMSECV, and RMSEP were all less than 1.6, 2.9, and 3.6%, respectively. The results obtained here indicated that NIR with chemometric methods was accurate for qualitative and quantitative analysis of drug samples. This methodology provided a potentially useful alternative to time-consuming gas chromatography-mass spectroscopy and high-performance liquid chromatography methods.

[Study on the methods and applications of near-infrared spectroscopy chemical pattern recognition].

Near infrared spectroscopy pattern recognition technique is an important part of modern near infrared spectroscopy technique. In the present paper, main methods of near infrared spectroscopy chemical pattern recognition and some recent developments are introduced. Basic principles of the methods in cluster analysis, discriminant analysis and latent projection are discussed, including some new methods such as support vector machines (SVM), bubble agglomeration algorithm (BA) and focal eigen functions (FEF) etc. Finally, the applications of near infrared spectroscopy pattern recognition technique in agriculture, pharmaceutical industry, food analysis, petroleum industry and other fields are reviewed.

[Interaction between carbaryl and calf thymus DNA enhanced via Cu2+].

The interaction between carbaryl and calf thymus DNA with Cu2+ was studied using fluorescence spectroscopy (FS) and UV spectrum. The quenching process was proved to be single static quenching and the quenching constant decreases with temperature increasing. The experimental results showed that the carbaryl can be intercalated into the twin-screw structure of calf thymus DNA, forming ctDNA-carbaryl adducts. The UV spectrum showed that ctDNA can also result in the increasing color and red shift. In the presence of Cu2+, it was discovered that the apparent association constant (Kalpha) increases and the binding sites number (n) of carbaryl molecules on ctDNA obviously increases. The interaction of the carbaryl and ctDNA was driven mainly by electrostatic force which was enhanced by Cu2+, thus the contribution of deltaH to deltaG increased in the presence of Cu2+ So the interaction between carbaryl and calf thymus DNA was enhanced via Cu+.

[The mechanism of carbofuran interacts with calf thymus DNA].

Carbofuran is an insecticide used on a variety of corps. Acute and chronic occupational exposure of humans to carbofuran has been observed to cause cholinesterase inhibition, but little is known about the interaction of carbofuran with DNA. Using the technique of UV spectrum and fluorescence quenching respectively, the interaction between carbofuran and ct DNA was studied. The UV spectrum showed that ct DNA can lead to the hypochromic effect and red shift of the UV spectrum of carbofuran. The quenching process was proved to be the single static quenching and quenching constant decreases with temperature increasing. The basis of this specificity is intercalation of insecticide between base pairs to produce ct DNA-carbofuran adducts. Furthermore, ethanol can produce Franck-condon effect on the ct DNA-carbofuran adducts. At different sodium chloride concentrations, quenching constant had no significant change, which appeared that there was little electrostatic interaction between ct DNA and carbofuran and it was intercalation.