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.     

High-performance capillary electrophoretic analysis of synthetic food colorants

Summary A high-performance capillary electrophoresis method with diode-array detection has been developed for analysis of synthetic food colorants. The influence of buffer composition on the separation of the food colorants was examined, as were the effects of α-, β- and γ-c-yclodextrins on analyte migration behavior. Eight food colorants were completely separated within 10 min using pH 9.5 borax—NaOH buffer containing 5 mM β-cyclodextrin. Experimental results indicate that the relative standard deviations of analyte migration times were<0.88% under the optimized separation condition. Correlation coefficients of the linear calibration plots of the analytes exceeded 0.998. The method was suitable for determination of the quantities of synthetic food colorantsi in ice cream bars and fruit soda drinks.     

导数伏安法同时测定5种混合人工合成色素

建立了同时测定胭脂红、柠檬黄、日落黄、赤藓红、苋菜红5种食用人工合成色素的1.5次线性扫描伏安法,并讨论了人工合成色素在悬汞电极上的反应机理.本方法简单快速,灵敏度高,重现性好,可以不经分离同时测定食品中的多种着色剂.     

Multicomponent kinetic spectrophotometric determination of pefloxacin and norfloxacin in pharmaceutical preparations and human plasma samples with the aid of chemometrics

A spectrophotometric method for the simultaneous determination of the important pharmaceuticals, pefloxacin and its structurally similar metabolite, norfloxacin, is described for the first time. The analysis is based on the monitoring of a kinetic spectrophotometric reaction of the two analytes with potassium permanganate as the oxidant. The measurement of the reaction process followed the absorbance decrease of potassium permanganate at 526nm, and the accompanying increase of the product, potassium manganate, at 608nm. It was essential to use multivariate calibrations to overcome severe spectral overlaps and similarities in reaction kinetics. Calibration curves for the individual analytes showed linear relationships over the concentration ranges of 1.0-11.5mgL(-1) at 526 and 608nm for pefloxacin, and 0.15-1.8mgL(-1) at 526 and 608nm for norfloxacin. Various multivariate calibration models were applied, at the two analytical wavelengths, for the simultaneous prediction of the two analytes including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), radial basis function-artificial neural network (RBF-ANN) and principal component-radial basis function-artificial neural network (PC-RBF-ANN). PLS and PC-RBF-ANN calibrations with the data collected at 526nm, were the preferred methods-%RPE(T) approximately 5, and LODs for pefloxacin and norfloxacin of 0.36 and 0.06mgL(-1), respectively. Then, the proposed method was applied successfully for the simultaneous determination of pefloxacin and norfloxacin present in pharmaceutical and human plasma samples. The results compared well with those from the alternative analysis by HPLC.     

Simultaneous determination of iron and aluminium by differential kinetic spectrophotometric method and chemometrics

A differential kinetic spectrophotometric method was researched and developed for the simultaneous determination of iron and aluminium in food samples. It was based on the direct reaction kinetics and spectrophotometry of these two metal ions with Chrome Azurol S (CAS) in ethylenediamine-hydrochloric acid buffer (pH 6.3). The results were interpreted with the use of chemometrics. The kinetic runs and the visible spectra of the complex formation reaction were studied between 540 and 750 nm every 30 s over a total period of 285 s. A set of synthetic metal mixture samples was used to build calibrations models. These were based on the spectral and kinetic two-way data matrices, which were processed separately by the radial basis function-artificial neural network (global RBF-ANN) method. The prediction performance of these models was poorer than that from the combined kinetic-spectral three-way array, which was similarly processed by the same method (% relative prediction error (RPE_T) = 5.6). These results demonstrate that improved predictions can be obtained from the data array, which has more information, and that appropriate chemometrics methods can enhance analytical performance of simple techniques such as spectrophotometry.Other chemometrics models were then applied: N-way partial least squares (NPLS), parallel factor analysis (PARAFAC), back propagation-artificial neural network (BP-ANN), single radial basis function-artificial neural network (RBF-ANN), and principal component neural network (PC-RBF-ANN). There was no substantial difference between the methods with the overall %RPE_T range being 5.0-5.8. These two values corresponded to the NPLS and BP-ANN models, respectively. The proposed method was applied for the determination of iron and aluminium in some commercial food samples with satisfactory results.     

Simultaneous kinetic determination of secondary amines and their isomers by a spectrophotometric stopped-flow method based on the formation of dialkyldithiocarbamates

Secondary amines react with carbon disulphide to form stable dialkyldithiocarbamates at high pH in aqueous Triton X-100 solution. The formation rates of dimethyl-, diethyl-, di-n-propyl-, diisopropyl-, di-n-butyl- and diisobutyldithiocarbamates and pyrrolidinedithiocarbamate were measured by a stopped-flow spectrophotometric method. The reaction rates were a function of the pH of the solution and depended on the size and structure of the amines. The rate of isoalkylamines was far slower than that of the n-alkyl analogues. Individual concentrations of amines were determined in a mixture of di-n- and diisopropylamine and in a mixture of diiso- and di-n-butylamine.     

Sensitive spectrophotometric kinetic determination of osmium by catalysis of the pyrogallol red-bromate reaction

Osmium(VIII) is determined by means of its catalytic effect on the oxidation of pyrogallol red (PGR) by potassium bromate at pH 6.0, 30°C and 545 nm. The decrease in absorbance of PGR (2.5 × 10^?5 M) in the presence of KBrO₃ (0.20 M) over a period of 0–150 s is proportional to the concentration of osmium(VIII) over the range 0–1400 ng ml^?1. The limit of detection of osmium was 0.65 ng ml^?1. The precision and accuracy of the method are described. The effects of the presence of 45 cations and anions on osmium determination were studied. The effects of probable interferences were completely removed by a single extraction of osmium as osmium tetraoxide into isobutyl methyl ketone and back-extraction into sodium hydroxide solution.     

Simultaneous spectrophotometric kinetic determination of four flavor enhancers in foods with the aid of chemometrics

A sensitive kinetic spectrophotometric method was developed for the determination of four flavor enhancers--maltol, ethyl maltol, vanillin, and ethyl vanillin--in food samples. The method was based on the reduction of iron(III) by the four analytes in a sulfuric acid medium (0.012 mol/L), and the subsequent interaction of iron(II) with hexacyanoferrate(III) to form the strongly colored Prussian blue complex, which exhibited an absorption maximum at 800 nm. The optimized method had linear calibrations over the concentration ranges of 0.2-2.8 mg/L for maltol, ethyl maltol, and vanillin, as well as 0.2-1.8 mg/L for ethyl vanillin; the corresponding detection limits were 0.07, 0.07, 0.06, and 0.06 mg/L, respectively. Calibration models were constructed from the original and first-derivative spectral data with the use of partial least-squares (PLS) and principal component regression chemometrics methods. Ultimately, the proposed analytical procedure was successively applied for the determination of the four compounds in commercial food samples with the use of a PLS calibration based on the first-derivative spectral data. The results were comparable with those from a reference HPLC method.     

Application of chemometric methods to the simultaneous kinetic spectrophotometric determination of iodate and periodate based on consecutive reactions

A kinetic spectrophotometric method for the simultaneous determination of iodate and periodate in mixtures was proposed. The method is established on the different kinetic behaviours of the analytes which react with starch–iodide in the presence of sodium chloride in sulfuric acid medium. The kinetic data were collected from 260 to 900 nm every 10 nm, within a time range of 0–180 s at 1 s interval, and the absorbance collected at 291, 354 and 585 nm, respectively, increased linearly with the concentration between 0.1–1.2 mg L^− 1 for both iodate and periodate. The mechanism investigation revealed that the iodate/periodate–iodide–starch system is a consecutive reaction. Subsequently, the mathematical model for the quantitative kinetic determination based on the consecutive reactions by utilizing chemometric methods was deduced, and the simultaneous determination of synthetic mixtures of iodate and periodate was then applied. Kinetic data collected at 291, 354 and 585 nm, were processed by chemometric methods, such as classical least square (CLS), principal component regression (PCR), partial least square (PLS), back-propagation artificial neural network (BP-ANN), radial basis function–artificial neural network (RBF-ANN) and principle component–radial basis function–artificial neural network (PC-RBF-ANN). The results showed that calibration model with the data collected at 354 nm had some advantages for the prediction of the analytes as compared with the ones of other two wavelengths, and the PLS and PC-RBF-ANN gave the lower prediction errors than other chemometric methods. The proposed method was applied to the simultaneous determination of iodate and periodate in several real samples; and the standard addition method yielded satisfactory recoveries in all instances.     

Simultaneous enzymatic kinetic determination of pesticides, carbaryl and phoxim, with the aid of chemometrics

A sensitive and selective enzymatic kinetic method for the simultaneous determination of mixtures of carbaryl and phoxim pesticides was researched and developed. It was based on the inhibitory effect of the pesticides on acetylcholinesterase (AChE), and the use of 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) as a chromogenic reagent for the thiocholine iodide (TChI) released from the acetylthiocholine iodide (ATChI) substrate. The DTNB-thiocholine reaction was investigated by a spectrophotometric-kinetic approach. The complex rate equation for the formation of the chromogenic product, P, was solved under certain experimental conditions, which enabled the absorbance (A_P, at λ_max = 412 nm) from the mixtures of the two pesticide inhibitors to be directly related to their concentrations provided the absorbance additivity was followed. The spectra were measured for mixtures of carbaryl and phoxim at different concentrations, and at t = 904 s, T = 35 °C, pH = 7.5, c_ATChI = 0.14, and c_AChE = 0.10 mg mL⁻¹. The detection limits of the enzymatic kinetic spectrophotometric procedures for the determination of the carbaryl and phoxim were 4.7 and 0.59 μg L⁻¹, respectively.Calibration models for chemometrics methods, such as principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural network (RBF-ANN) were constructed and verified with synthetic samples of the mixtures of the two pesticides. The best performing model was based on the RBF-ANN method yielding at approximately 10 ppb analyte concentrations, %RPE_T (carbaryl = 5.2; phoxim = 6.5), %Recovery (approx.105%) and %RPE_T (6.5). Various spiked town-water samples produced recoveries in the range of 98.8-103% for each pesticide.     

Application of potassium ferricyanide in the spectrophotometric determination of captopril

A novel method for the determination of captopril by speetrophotometer is described in this paper. The experiment is based on the fact that Fe(Ⅲ) is reduced to Fe(Ⅱ) by captopril, then the in situ formed Fe(Ⅱ) reacts with potassium ferricyanide to give the soluble prussian blue at pH 4.00, and its maximal adsorption wavelength (λmax) is 735 nm. Good linear relationship is obtained between the absorbance and the concentration of captopril in the wide range of 0.05-20 μg/mL. The linear regression equation is A = -0.04314 + 0.11423C (μg/mL) with a correlation coefficient R = 0.9998. The detection limit (3a/k) is 0.04 μg/mL, the molar absorption coefficient is 2.5×104 L/mol cm. By mensurating the absorbance of soluble prussian blue, the indirect determination of eaptopril can be obtained. This method has been successfully applied to determination of captopril in pharmaceutical samples.Analytical results obtained are satisfactory.     

Simultaneous determination of three fluoroquinolones by linear sweep stripping voltammetry with the aid of chemometrics

A linear sweep stripping voltammetric (LSSV) method has been researched and developed for simultaneous quantitative determination of mixtures of three antibiotic drugs, ofloxacin, norfloxacin and ciprofloxacin. It relies on reductive reaction of the antibiotics at a mercury electrode in a Britton-Robinson buffer (pH 3.78). The voltammograms of these three compounds overlap strongly, and show non-linear character. Thus, it is difficult to analyse the compounds individually in their mixtures. In this work, chemometrics methods such as classical least squares (CLS), principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural networks (RBF-ANN) were applied for the simultaneous determination of these compounds. The prediction performance of the calibration models constructed on the basis of these methods was compared. It was shown that satisfactory quantitative results were obtained with the use of the RBF-ANN calibration model relative prediction error (RPE_T) of 8.1% and an average recovery of 101%. This method is able to accommodate non-linear data quite well. The proposed analytical method based on LSSV was applied for the analysis of ofloxacin, norfloxacin and ciprofloxacin antibiotics in bird feedstuffs and their spiked samples, as well as in eye drops with satisfactory results.     

A kinetic spectrophotometric method for the determination of ternary mixtures of reducing sugars with the aid of artificial neural networks and multivariate calibration

A differential spectrophotometric method has been developed for the simultaneous quantitative determination of glucose (GLU), fructose (FRU) and lactose (LAC) in food samples. It relies on the different kinetic rates of the analytes in their oxidative reaction with potassium ferricyanide (K₃Fe(CN)₆) as the oxidant. The reaction data were recorded at the analytical wavelength (420 nm) of the K₃Fe(CN)₆ spectrum. Since the kinetic runs of glucose, fructose and lactose overlap seriously, the condition number was calculated for the data matrix to assist with the optimisation of the experimental conditions. Values of 80 °C and 1.5 mol l⁻¹ were selected for the temperature and concentration of sodium hydroxide (NaOH), respectively. Linear calibration graphs were obtained in the concentration range of 2.96-66.7, 3.21-67.1 and 4.66-101 mg l⁻¹ for glucose, fructose and lactose, respectively. Synthetic mixtures of the three reducing sugar were analysed, and the data obtained were processed by chemometrics methods, such as partial least square (PLS), principal component regression (PCR), classical least square (CLS), back propagation-artificial neural network (BP-ANN) and radial basis function-artificial neural network (RBF-ANN), using the normal and the first-derivative kinetic data. The results show that calibrations based on first-derivative data have advantages for the prediction of the analytes and the RBF-ANN gives the lowest prediction errors of the five chemometrics methods. Following the validation of the proposed method, it was applied for the determination of the three reducing sugars in several commercial food samples; and the standard addition method yielded satisfactory recoveries in all instances.     

Simultaneous enzymatic kinetic determination of carbamate pesticides with the aid of chemometrics

A method for the simultaneous enzymatic kinetic determination of the pesticides, oxamyl, aldicarb and aminocarb in fruit, vegetables and water samples, has been researched and developed. It was based on enzymatic reaction kinetics and spectrophotometric measurements, and results were interpreted with the aid of chemometrics. The analytical method relies on the inhibitory effect of the pesticides on acetylcholinesterase (AChE), and the use of 5,5′-dithiobis (2-nitrobenzoic) acid (DTNB) as a chromogenic reagent for the thiocholine iodide (TChI) released from the acetylthiocholine iodide (ATChI) substrate. The complex rate equation for the formation of the chromogenic product, P, was solved under certain experimental conditions, and this enabled the absorbance (A _p, at λ _max = 412 nm) from the mixtures of the three pesticide inhibitors to be directly related to their concentrations. The detection limits of the enzymatic kinetic spectrophotometric procedures for the determination of the oxamyl, aldicarb and aminocarb were 0.81, 2.13 and 1.25 ng mL^?1, respectively. Calibration models were constructed for principal component regression (PCR), partial least squares (PLS), and radial basis function-artificial neural network (RBF-ANN), and verified with synthetic samples of the three pesticides. The prediction performance of these models showed generally satisfactory results, and the RBF-ANN one performed slightly better than the other two (RPE_T = 7.59% and average %recovery = 99%). This model was then successfully applied to estimate the amounts of the three compounds in fruit, vegetables and water with satisfactory results.     

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02-3.50 μg mL⁻¹ for carmoisine and 0.05-3.50 μg mL⁻¹ for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.017 and 0.016 μg mL⁻¹ (n = 10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 μg mL⁻¹ was 4.14 and 3.30% (n = 10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.     

Exploiting kinetic spectrophotometric determination of captopril, an angiotensin-converting enzyme inhibitor, in a multi-pumping flow system

The implementation of a differential kinetic spectrophotometric method for the determination of angiotensin-converting-enzyme inhibitors in pharmaceutical formulations is described. The determination method was based on the monitoring (350 nm) of the reaction between captopril and iodate, in the presence of iodide, versus time and was fully automated by exploiting the multi-pumping flow concept. The developed multi-pumping flow system included four discretely actuated solenoid micro-pumps as unique flow manifold active components. The automatic control of the solenoid micro-pumps, under time-based and pulse-counting routines, allowed the implementation of a reliable and versatile analytical determination, with the additional advantage of permitting a runtime access to important analytical parameters, such as flow rate, sample insertion and reagent addition synchronisation, facilitating this way the establishment of an approach for kinetic measurements, directly due to the efficient solution handling and accurate timing control.

A linear range of determination was verified for captopril concentrations between 10.0 and 60.0 μg mL⁻¹ with a sample throughput of about 100 determinations per hour. The results were in agreement with those obtained by the reference procedure with relative deviations between 1.81 and 4.48%.     

Determination of 13 synthetic food colorants in water-soluble foods by reversed-phase high-performance liquid chromatography coupled with diode-array detector

A reversed-phase high performance liquid chromatographic method for the successful separation and determination of 13 synthetic food colorants (Tartrazine E 102, Quinoline Yellow E 104, Sunset Yellow E 110, Carmoisine E 122, Amaranth E 123, Ponceau 4R E 124, Erythrosine E 127, Red 2G E 128, Allura Red AC E 129, Patent Blue V E 131, Indigo Carmine E 132, Brilliant Blue FCF E 133 and Green S E 142) was developed. A C18 stationary phase was used and the mobile phase contained an acetonitrile-methanol (20:80 v/v) mixture and a 1% (m/v) ammonium acetate buffer solution at pH 7.5. Successful separation was obtained for all the compounds using an optimized gradient elution within 29 min. The diode-array detector was used to monitor the colorants between 350 and 800 nm. The method was thoroughly validated. Detection limits for all substances varied between 1.59 (E 142) and 22.1 (E 124) μg L⁻¹. The intra-day precision (as R.S.D._r) ranged from 0.37% (E 122 in fruit flavored drink at a concentration of 100 mg L⁻¹) to 4.8% (E 142 in icing sugar at a level of 0.9 mg kg⁻¹). The inter-day precision (as R.S.D._R) was between 0.86% for E 122 in fruit flavored drink at 100 mg L⁻¹ and 10% for E142 in jam at a concentration of 9 mg kg⁻¹. Satisfactory recoveries, ranging from 94% (E 142 in jam) to 102% (E 131 in sweets), were obtained. The method was applied to the determination of colorants in various water-soluble foods, such as fruit flavoured drinks, alcoholic drinks, jams, sugar confectionery and sweets, with simple pre-treatment (dilution or water extraction).     

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

<正>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(K_a) 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).     

Nondestructive determination of compound amoxicillin powder by NIR spectroscopy with the aid of chemometrics

Near-infrared (NIR) spectroscopy, in combination with chemometrics, enables nondestructive analysis of solid samples without time-consuming sample preparation methods. A new method for the nondestructive determination of compound amoxicillin powder drug via NIR spectroscopy combined with an improved neural network model based on principal component analysis (PCA) and radial basis function (RBF) neural networks is investigated. The PCA technique is applied to extraction relevant features from lots of spectra data in order to reduce the input variables of the RBF neural networks. Various optimum principal component analysis-radial basis function (PCA-RBF) network models based on conventional spectra and preprocessing spectra (standard normal variate (SNV) and multiplicative scatter correction (MSC)) have been established and compared. Principal component regression (PCR) and partial least squares (PLS) multivariate calibrations are also used, which are compared with PCA-RBF neural networks. Experiment results show that the proposed PCA-RBF method is more efficient than PCR and PLS multivariate calibrations. And the PCA-RBF approach with SNV preprocessing spectra is found to provide the best performance.     

Authentication of vegetable oils on the basis of their physico-chemical properties with the aid of chemometrics

In food production, reliable analytical methods for confirmation of purity or degree of spoilage are required by growers, food quality assessors, processors, and consumers. Seven parameters of physico-chemical properties, such as acid number, colority, density, refractive index, moisture and volatility, saponification value and peroxide value, were measured for quality and adulterated soybean, as well as quality and rancid rapeseed oils. Chemometrics methods were then applied for qualitative and quantitative discrimination and prediction of the oils by methods such exploratory principal component analysis (PCA), partial least squares (PLS), radial basis function-artificial neural networks (RBF-ANN), and multi-criteria decision making methods (MCDM), PROMETHEE and GAIA.In general, the soybean and rapeseed oils were discriminated by PCA, and the two spoilt oils behaved differently with the rancid rapeseed samples exhibiting more object scatter on the PC-scores plot, than the adulterated soybean oil. For the PLS and RBF-ANN prediction methods, suitable training models were devised, which were able to predict satisfactorily the category of the four different oil samples in the verification set. Rank ordering with the use of MCDM models indicated that the oil types can be discriminated on the PROMETHEE II scale. For the first time, it was demonstrated how ranking of oil objects with the use of PROMETHEE and GAIA could be utilized as a versatile indicator of quality performance of products on the basis of a standard selected by the stakeholder. In principle, this approach provides a very flexible method for assessment of product quality directly from the measured data.