Investigation of the interaction of carbofuran and DNA by voltammetry and fluorescence with the aid of chemometrics

The interactions of carbofuran and DNA were studied using voltammetry and fluorescence spectroscopy.The formation of carbofuran-DNA makes the current peak of DNA decreased by voltammetry method.The binding number（n） and constant（Ka） for complex carbofuran-DNA were calculated to be 1.06±0.04 and 0.11±0.03mol^-1 L,respectively by fluorescence measurement.Chemometrics approach,such as singular value decomposition（SVD） was used to evaluate the number of spectral species in the drug-DNA binding process.And the pure spectra and concentration profiles in the kinetic system were clearly deduced by multivariate curve resolution alternating least squares（MCR-ALS） with the initial estimates by evolving factor analysis（EFA）.

Geographical origin identification of winter jujube(Ziziphus jujuba Dongzao')by using multi-element fingerprinting with chemometrics

Winter jujube(Ziziphus jujuba'Dongzao')is greatly appreciated by consumers for its excellent quality,but brand infringement frequently occurs in the market.Here,we first determined a total of 38 elements in 167 winter jujube samples from the main winter jujube producing areas of China by inductively coupled plasma mass spectrometer(ICP-MS).As a result,16 elements(Mg,K,Mn,Cu,Zn,Mo,Ba,Be,As,Se,Cd,Sb,Ce,Er,Tl,and Pb)exhibited significant differences in samples from different producing areas.Supervised linear discriminant analysis(LDA)and orthogonal projection to latent structures discriminant analysis(OPLS-DA)showed better performance in identifying the origin of samples than unsupervised principal component analysis(PCA).LDA and OPLS-DA had a mean identification accuracy of 87.84 and 94.64%in the testing set,respectively.By using the multilayer perceptron(MLP)and C5.0,the prediction accuracy of the models could reach 96.36 and 91.06%,respectively.Based on the above four chemometric methods,Cd,Tl,Mo and Se were selected as the main variables and principal markers for the origin identification of winter jujube.Overall,this study demonstrates that it is practical and precise to identify the origin of winter jujube through multi-element fingerprint analysis with chemometrics,and may also provide reference for establishing the origin traceability system of other fruits.

Simultaneous Voltammetric Determination of Three Herbicides in Food and Water Samples with the Aid of Chemometrics

Differential pulse stripping voltammetry method（DPSV） was applied to the determination of three herbicides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it is difficult to determine these compounds individually from their mixtures. With the aid of chemometrics, classical least squares（CLS）, principal component regression（PCR） and partial least squares（PLS）, voltammogram resolution and quantitative analysis of the synthetic mixtures of the three compounds were successfully performed. The proposed method was also applied to the analysis of some real samples with satisfactory results.

Simultaneous determination of three 5-nitroimidazoles in foodstuffs by differential pulse voltammetry and chemometrics

The voltammetric behaviour of three 5-nitroimidazoles,metronidazole,tinidazole and ornidazole,was investigated,and a method was developed for the simultaneous determination of these compounds,based on their reduction at a hanging mercury drop electrode（HMDE） in pH 8.95 buffer with differential pulse voltammetric（DPV） approach.Well defined voltammetric waves with peak potentials of -692,-640 and -652 mV were observed for these compounds,respectively.It is difficult to determine them individually from their mixtures without preseparation,for their voltammetric peaks overlapped seriously,so the chemometrics were used to resolve the overlapped voltammogram and quantify the mixtures.The proposed method was successfully applied to the determination of three 5-nitroimidazoles in milk and honey samples.

Application of differential pulse stripping voltammetry and chemometrics for the determination of three antibiotic drugs in food samples

A reliable method for simultaneous determination of three antibiotic drugs（levofloxacin,gatifloxacin and lomefloxacin） by differential pulse stripping voltammetry（DPSV） in Britton-Robinson buffer（pH 7.96） was presented.The method is based on adsorptive accumulation of the antibacterial drugs on a hanging mercury dropping electrode（HMDE）,followed by the reduction of the adsorptive species by the technique of DPSV.Optimal conditions,the deposition time of 80 s,the deposition potential of—1250 mV,and the scan rate of 25 mV/s,were obtained.The linear concentration ranges of 0.010-0.080μg/mL were obtained for all these three antibiotic drugs,while the detection limits were 2.38,3.20 and 1.60ng/mL for levofloxacin,gatifloxacin and lomefloxacin,respectively.In this work,chemometrics methods,such as classical least squares（CLS）,partial least squares（PLS）, principle component regression（PCR） and radial basis function-artificial neural networks（RBF-ANN）,were used to quantitatively resolve the overlapping signals.It was found that PCR gave the best results with total relative prediction error（RPE_T） of 7.71%.The proposed method was applied to determine these three drugs in several commercial food samples with spiked method and yielded satisfactory recoveries.

Determination of trace amount of antimony (Ⅲ) by adsorption voltammetry on carbon paste electrode

A sensitive method is described for the determination of trace antimony based on the antimony-bromopyrogallol red (BPR) adsorption at a carbon paste electrode (CPE). Three steps were involved in the overall analysis: preconcentration,reduction and stripping. Optimal conditions were found to be an electrode containing 25% paraffin oil and 75% high purity graphite powder as working electrode;a 0.10 mol/L HCl solution containing 40 μmol/L BPR as accumulation medium;a 0.20 mol/L HCl solution as reduction and stripping electrolyte;accumulation time,150 s;reduction potential and time,-0.50 V,60 s;scan range from -0.50 to 0.20 V. Interferences by other ions were studied as well. The detection limit was found to be 0.5 nmol/L for 150 s preconcentration. The linear range was from 1.0 nmol/L to 0.50 μmol/L. Application of the proposed method to the determination of antimony in water and human hair samples gave good results.

Simultaneous spectrophotometric determination of cobalt,copper and nickel using 1-(2-thiazolylazo)-2-naphthol by chemometrics methods

The simultaneous determination of cobalt, copper and nickel using 1-（2-thiazolylazo）-2-naphthol （first figure of this article） by spectrophotometric method is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares （PLS） regression, it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction （OSC） is a preprocessing technique used for removing the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 550-750-nm range for 21 different mixtures of cobalt, copper and nickel. Calibration matrices were formed from samples containing 0.05-1.05, 0.05-1.30 and 0.05-0.80 μg·mL^-1 for cobalt, copper and nickel, respectively. The root mean square error of prediction （RMSEP） for cobalt, copper and nickel with OSC and without OSC were 0.007, 0.008, 0.011 and 0.031,0.037, 0.032 μg· mL^-1, respectively. This procedure allows the simultaneous determination of cobalt, copper and nickel in synthetic and real samples and good reliability of the determination was proved.

Authentication of Cassia seeds on the basis of two-wavelength HPLC fingerprinting with the use of chemometrics

High performance liquid chromatographic(HPLC) fingerprints of Cassia seed,a traditional Chinese medicine(TCM),were developed by means of the chromatograms at two wavelengths of 238 and 282 nm.Then,the two data sets were combined into one matrix.The application of principal component analysis(PCA) for this data matrix showed that the samples were clustered into four groups in accordance with the plant sources and preparation procedures.Furthermore,partial least squares(PLS),back propagation artificial neural...

Trace Determination of Scandium Using Adsorption Voltammetry of Mix-Polynuclear Complex of Scandium-Calcium-Alizarin Red S at Carbon Paste Electrode

A novel method was described for the determination of ultra trace amount of scandium based on the cathodic adsorptive voltammetry of the mix-polynuclear complex of scandium-calcium-alizarin red S at a carbon paste electrode (CPE). The 2nd-order derivative linear scan voltammograms of the adsorbed complex were recorded by model JP-303 polarographic analyzer from 0.0 to -1.0 V (vs. SCE). The experimental conditions of the working procedure were optimized. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at -0.61 V, corresponding to the reduction of the alizarin red S in the mix-polynuclear complex at the electrode. The detection limit of Sc^(3+) is 1.0×10^(-10) mol·L^(-1) for 3 min of accumulation time. The procedure was successfully applied to the determination of trace amount of scandium in the sample ores.

Simultaneous kinetic spectrophotometric determination of cephalexin and trimethoprim in pharmaceutical preparation and human urine with the aid of chemometrics

A procedure for the simultaneous kinetic spectrophotometric determination of cephalexin and trimethoprim was described. It was based on the different reaction rate of oxidation of these compounds with yellow ammonium cerous （Ⅳ） sulfate in acidic medium and colorless cerous （Ⅲ） sulfate was produced. The overlapped kinetic data was quantitatively resolved by the use of chemometric methods, partial least squares （PLS）, principal component regression （PCR） and radial basis function-artificial neural network （RBF-ANN）. The proposed method was also applied to the simultaneous determination of cephalexin and trimethoprim in pharmaceutical preparation and human urine with satisfied results, which compared well with those obtained by HPLC.

Determination of trace amounts of morphine in human plasma by anodic adsorptive stripping differential pulse voltammetry

New adsorptive anodic differential pulse stripping voltammetry method for the direct determination of morphine at trace levels in human plasma of addicts is proposed.The procedure involves an adsorptive accumulation of morphine on a HMDE,followed by oxidation of adsorbed morphine by voltammetry scan using differential pulse modulation.The optimum conditions for the analysis of morphine are pH 10.5,Eacc of -100 mV（vs.Ag/AgCl）,and tacc of 120 s.The peak current is proportional to the concentration of morphine,and a Linear calibration graph is obtained at 0.01-3.10μg mL^-1.A relative standard deviation of 1.06%（n=5）was obtained,and the limit of detection was 3 ng mL^-1.The capabiLity of the method for the analysis of real samples was evaluated by the determination of morphine in spiked human plasma and addicts human plasma with satisfactory results.

Interaction between Eu-phenylalanine and DNA Using Cyclic Voltammetry and UV Spectroscopy

The interaction between DNA and the Eu(Phe) 3+ 3 complex ion has been studied by means of cyclic voltammetry and differential UV spectroscopy The results depicted an obvious decrease of peak current in CV plot after the reaction between the two species studied The observed peak potential separation was increased but the diffusion coefficient of Eu complex ion was decreased Hypochromicity was observed at 226 and 258 nm after the predicted interaction of them A preliminary interpretation is proposed for discussion

Amperometric detection of gold by differential pulse voltammetry using a DNA biosensor

A DNA biosensor with [Ru（DA-bpy）3]Cl2（DA-bpy：4,4＇-diamino-2,2＇-bipyridine） （RuL） as the electrochemical probe was prepared on pyrolytic graphite electrode （PGE） through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru（Ⅲ）/Ru（Ⅲ） redox potential of-0.165 V versus AglAgCl in pa 7.4 0.1 mol·L^-1Tris-HCl. The electron transfer was expected across the double-strand DNA by an ＂electron tunneling＂ mechanism. When the DNA biosensor was immerged in gold （Ⅲ） buffer solution, the current peak signal （I） of the RuL-DNA supramolecular depressed and △I was linear in the concentration range of Au ion from 1×10^-7 to 2×10^-5 mol·L^-1 with a regression coefficient of 0.9879. The detection limit was 5×10^-8 mol·L^-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.

Determination of Metamizole Sodium by Cyclic Voltammetry Under Microwave Activation

Microwave radiation was applied to the detection of metamizole sodium by cyclic voltammetry. The electrochemical characteristics of metamizole sodium were studied by cyclic voltammetry at GC electrode under microwave radiation and a considerable current enhancement was observed for metamizole sodium in aqueous 0.05 mol/L H2SO4. Under the optional conditions, metamizole sodium was determined in the absence and presence of microwave activation. In the absence of microwave activation cyclic voltammogram of metamizole sodium shows good linear relationship in a concentration range of 8.0×10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 6.75× 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=12.973c-0.1905（R^2=0.9996, n=6）; in the presence of 80 W microwave activation cyclic voltammogram of metamizole sodiumin shows good linear relationship in a concentration range of 4.0× 10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 4,41 × 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=25.107c-0.1193（R^2=0.9973, n=7）. The current in the presence of 80 W microwave activation increases to about 2 orders of magnitude compared with that in the absence of microwave activation. The proposed method in the presence of microwave activation showed high selectivity and sensitivity, and the sampling of the disposal method is simple. The method was verified by the determination of Metamizole Sodium tablet with satisfactory results.

Cyclic Voltammetry Determination of Epinephrine with a Nano-gold Modified Glassy Carbon Electrode in the Presence of High Concentration Ascorbic Acid

Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can not only catalytically oxidize EP and AA, but also separate the catalytic peak potentials of EP and AA by about 183.5 mV. In pH = 7.0 ogisogate byffer solution, the linear range of epinephrine was 5 106 ~ 1 ?10-4 mol/L.

Electrochemical Determination of Alkaline Phosphatase in Human Serum by Differential Pulse Voltammetry

Differential pulse voltammetry(DPV) was applied to the determination of alkaline phosphatase(ALP) activity in human serum with phenyl phosphate as the substrate. Phenyl phosphate can enzymatically be hydrolyzed to produce phenol which is quantified by DPV at +660 mV(vs.Ag/AgCl) in the concentration range of 2.0_100 μmol/L. The standard curve for ALP is linear over the range from 0.06 to 1000 U/L with a relative standard deviation of 3.0%. The conditions for the enzymatic reaction and voltammetric detection were optimized and the kinetic constants were also examined.The human serum samples were tested by this method and the results were in good agreement with those obtained by the routine p-nitrophenyl phosphate spectrophotometric method.

Rapid qualitative and quantitative analysis of strong aroma base liquor based on SPME-MS combined with chemometrics

To objectively classify and evaluate the strong aroma base liquors(SABLs)of different grades,solid-phase microextraction-mass spectrometry(SPME-MS)combined with chemometrics were used.Results showed that SPME-MS combined with a back-propagation artificial neural network(BPANN)method yielded almost the same recognition performance compared to linear discriminant analysis(LDA)in distinguishing different grades of SABL,with 84%recognition rate for the test set.Partial least squares(PLS),successive projection algorithm partial least squares(SPA-PLS)model,and competitive adaptive reweighed samplingpartial least squares(CARS-PLS)were established for the prediction of the four esters in the SABL.CARS-PLS model showed a greater advantage in the quantitative analysis of ethyl acetate,ethyl butyrate,ethyl caproate,and ethyl lactate.These results corroborated the hypothesis that SPME-MS combined with chemometrics can effectively achieve an accurate determination of different grades of SABL and prediction performance of esters.

Qualitative and quantitative evaluation of Flos Puerariae by using chemical fingerprint in combination with chemometrics method

In order to better control the quality of Flos Puerariae(FP),qualitative and quantitative analyses were initially performed by using chemical fingerprint and chemometrics methods in this study.First,the fingerprint of FP was developed by HPLC and the chemical markers were screened out by similarity analysis(SA),hierarchical clustering analysis(HCA),principal components analysis(PCA),and orthogonal partial least squares discriminant analysis(OPLS-DA).Next,the chemical constituents in FP were profiled and identified by HPLC coupled to Fourier transform ion cyclotron resonance mass spectrometry(HPLCFT-ICR MS).Then,the characteristic constituents in FP were quantitatively analyzed by HPLC.As a result,31 common peaks were assigned in the fingerprint and 6 of them were considered as qualitative markers.A total of 35 chemical constituents were detected by HPLC-FT-ICR MS and 16 of them were unambiguously identified by comparing retention time,UV absorption wavelength,accurate mass,and MS/MS data with those of reference standards.Subsequently,the contents of glycitin,genistin,tectoridin,glycitein,genistein,and tectorigenin in 13 batches of FP were detected,ranging from 0.4438 to 11.06 mg/g,0.955 to 1.726 mg/g,9.81 to 57.22 mg/g,3.349 to 41.60 mg/g,0.3576 to 0.989 mg/g,and 2.126 to 9.99 mg/g,respectively.In conclusion,fingerprint analysis in combination with chemometrics methods could discover chemical markers for improving the quality control standard of FP.It is expected that the strategy applied in this study will be valuable for further quality control of other traditional Chinese medicines.

SOLID STATE VOLTAMMETRY OF ELECTROACTIVE SOLUTES IN POLYMER SOLVENTS(PEO)AT MICROELECTRODE

The present paper describes experiments aimed at delineating significant chemical characteristics of electrochemical reactions in polymeric solutions, including how rigid solvent environments affect mass transport rates, and also discusses the possibility that the microelectrode coated with poly(ethylene oxide)(PEO) film can be used as gas sensor.