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）.

Investigation of the interaction of DNA and neutral red by fluorescence spectroscopic analysis

The binding characteristics of neutral red （NR） with DNA were investigated by fluorescence spectrometry. Chemometrics approach as singular value decomposition （SVD） was used to evaluate the number of spectral species in the drug-DNA binding process, and then the intrinsic binding constant of 1.6 × 10^4 in base pairs and the binding site number of 0.97 were obtained from the Scatchard plot.

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.

Simultaneous spectrophotometric determination of four preservatives in foodstuffs by multivariate calibration and artificial neural networks

Benzoic acid （BA）, methylparaben （MP）, propylparaben （PP） and sorbic acid （SA） are food preservatives, and they have well defined UV spectra. However, their spectra overlap seriously, and it is difficult to determine them individually from their mixtures without preseparation. In this paper, seven different chemometric approaches were applied to resolve the overlapping spectra and to determine these compounds simultaneously. With respect to the criteria of % relative prediction error （RPE） and % recovery, principal component regression （PCR） and radial basis function-artificial neural network （RBF-ANN） were the preferred methods. These two methods were successfully applied to the analysis of some commercial samples.

Osteryoung square wave voltammetric determination of lactose in food samples by a derivative procedure

A method for determination of lactose in food samples by Osteryoung square wave voltammetry （OSWV） was developed. It was based on the nucleophilic addition reaction between lactose and aqua ammonia. The carbonyl group of lactose can be changed into imido group, and this increases the electrochemical activity in reduction and the sensitivity. The optimal condition for the nucleophilic addition reaction was investigated and it was found that in NH4C1-NH3 buffer of pH 10.1, the linear range between the peak current and the concentration of lactose was 0.6-8.4 mg L-l, and the detection limits was 0.44 mg L- 1. The proposed method was applied to the ＇determination of lactose in food samples and satisfactory results were obtained.

Determination of ziram in vegetable samples by square wave voltammetry

The electrochemical behaviour and electrode reaction mechanism of ziram （zinc-dimethyl dithiocarbamate） on a hanging mercury drop electrode were investigated in Britton-Robinson （B-R） buffer by using cyclic and square wave voltammetry （SWV）. Based on these studies a voltammetric method for determination of ziram wasdeveloped and applied to determine the ziram in synthetic and spiked vegetable samples, satisfactory results were obtained in both cases.

Behavior and Quantification Studies of Phoxim Pesticide Using Cyclic and Linear Sweep Stripping Voltammetry at a Mercury Electrode

The adsorptive and electrochemical behaviour of phoxim on a hanging mercury drop electrode were explored in NH3·H2O-NH4Cl buffer by using cyclic and linear sweep voltmmetry. The procedure was successfully applied for the assay of phoxim in vegetable and fruit samples.

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.

Near-infrared spectra combined with partial least squares for pH determination of toothpaste of different brands

Near-infrared spectroscopy（NIR）,which is generally used for online monitoring of the food analysis and production process, was applied to determine the internal quality of toothpaste samples.It is acknowledged that the spectra can be significantly influenced by non-linearities introduced by light scatter,therefore,four data preprocessing methods,including off-set correction, 1st-derivative,standard normal variate（SNV） and multiplicative scatter correction（MSC）,were employed before the date analysis. The multivariate calibration model of partial least squares（PLS） was established and then was used to predict the pH values of the toothpaste samples of different brand.The results showed that the spectral date processed by MSC was the best one for predicting the pH value of the toothpaste 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.