[The application of near-infrared spectroscopy and pattern recognition to quality assessment of toothpaste samples of different brands].

The near-infrared spectroscopy (NIR) was combined with pattern recognitions method and applied to the quality assessment of toothpaste samples of four different brands. Several chemometrics approaches, such as principal component analysis (PCA), clustering analysis (CA), partial least squares (PLS), artificial neural networks (ANN) and K-nearest neighbor (kNN) were used to investigate the quality of toothpastes samples. The obtained results showed that the four clustering groups can be observed after the pretreatment of multiple scatter correction for the NIR data. It was also found that the quality of toothpastes of all the four brands was relatively stable, however, there is a significant difference in the quality between two brand kinds of toothpaste samples.

[Research on discrimination method of vinegar varieties and brands based on the content of inorganic elements].

Classification of brands and quality of food products is a very active area with the application of chemometric classification procedures. The content of inorganic elements such as Mg, K, Pb, Zn, Fe, Mn, Ca and Cu in 32 vinegar samples was determined by atomic absorption spectrophotometer. The similarity of Chencu and Baicu as well as different brands of vinegar samples of the same kind was calculated by vector similarity analysis. The characteristic discrimination of vinegar samples of four brands from Beijing, Jiangxi, Jiangsu and Shanxi was accomplished through cluster analysis and principal component analysis, and the classification of different kinds of vinegar samples (Chencu and Baicu) was performed as well. Vinegar samples were divided into two main groups by cluster analysis and principal component analysis. Each main group was discriminated according to different brands. The contents of inorganic elements in vinegar were good chemical descriptors for differentiation of their kinds and brands.

[Kinetic spectrophotometric determination of iodate in iodized salt samples].

A kinetic spectrophotometric method for the determination of iodate based on consecutive reactions was proposed. The method was based on the kinetic process of the analytes which react with starch-iodide in the presence of sodium chloride in sulfuric acid medium. It was found that the intermediate triiodide ion was produced in the consecutive reactions and the three peak wavelengths, 291, 354 and 585 nm, were obtained in the whole reaction process. And then the three peak wavelengths were chosen as the optimization conditions. In the reaction time of 180 s, the obtained linear calibration concentration ranges at the three peak wavelengths under the optimized conditions were 0.1-1.2, 0.05-1.2 and 0.1-1.2 microg x mL(-1), respectively, and the detection limits were 0.047, 0.027 and 0.048 microg x mL(-1), respectively. As there were the widest linear range and the lowest detection limit at the peak wavelength 354 nm, the wavelength was chosen for the quantitive ananlysis of iodate. At the same time, the method was successfully applied to the determination of iodate in iodized salt samples.

[Simultaneous determination of trace elements in mistletoe by ICP-AES].

A method for the simultaneous determination of elements Cu, Mg, Zn, Mn, Ni, Se, K, Na, Ca and Fe in mistletoe after HNO3-H2O2 digestion by ICP-AES was studied. The recoveries obtained by standard addition method were between 90.8% and 112.8%, while the RSD (n = 5) was in the range of 0.47%-4.59%. The results showed that there were rich K, Ca, Mg and Na in the mistletoe, and offered scientific data for the ulterior study on mistletoe.

[Simultaneous spectrophotometric determination of certain beta-lactam antibiotics in rabbit serum using multivariate calibration methods].

Cefuroxime sodium, ceftriaxone sodium, cefotaxime sodium and cefazolin sodium have absorption in ultraviolet region, and their absorption spectra are overlapping. So they can not be determined individually by spectrophotometry without prior separation. In this paper, the chemometric multivariate calibration method was applied to the simultaneous determination of these four compounds in a Britton-Robinson buffer solution (pH 2.09), and the analytical results were compared with those by classical least squares (CLS), principal components regression (PCR) and partial least squares (PLS). The linear ranges of cefuroxime sodium, ceftriaxone sodium, cefotaxime sodium and cefazolin sodium are 1.0-20.0, 2.0-20.0, 2.0-20.0 and 1.0-18.0 microg x mL(-1), respectively. The proposed procedure was successfully applied in the determination of these drugs in rabbit serum, and the result obtained from spectrophotometry was compared with the one by HPLC with no significant difference found.

[Differential kinetic spectrophotometric determination of chlorpromazine hydrochloride and promethazine hydrochloride by chemometric method].

Chlorpromazine hydrochloride and promethazine hydrochloride were oxidized fastly resulting in red intermediate product, which was then gradually changed into a colorless product by ammonium cerous sulfate in appropriate acidic medium. The chemometric multivariate calibration methods, such as partial least squares (PLS) and principal components regression (PCR) were applied to the resolution of the kinetic curves to determine these two compounds. The linear ranges are 8.3 - 66.7 mg x L(-1) and 3.3 - 26.7 mg x L(-1) for chlorpromazine and promethazine, respectively. The limits of detections are 2.32 and 0.95 mg x L(-1) for these two compounds, respectively. This method was successfully applied to the analysis of pharmaceutical samples with satisfied results.

[Resolution of synchronous fluorimetric spectrum for carbaryl and coumaphos and its application study].

The synchronous fluorimetric method for the simultaneous determination of carbaryl and coumaphos is described. In the Britton-Robinson buffer at pH 3.0, synchronous scanning with deltalambda= 60 nm was carried out, and the overlapped fluorimetric spectra were better separated. The two synchronous fluorimetric peaks are located at 280 and 322 nm respectively, and can be used for the determination of these two pesticides. No preliminary separation is needed. The method is simple, rapid and successfully applied to the analysis of food samples. The linear ranges of the calibration curves for carbaryl and coumaphos are 0.016-0.384 microg x mL(-1) and 0.016-0.320 microg x mL(-1), respectively. The limits of detection are 0.015 microg x mL(-1) for carbaryl, and 0.010 microg x mL(-1) for coumaphos.

[Synchronous fluorimetric determination of the residues of three quinolones in Eel by partial least squares].

In the present paper, the synchronous fluorimetric spectra of norfloxacin, lomefloxacin chlorhydric acid, and levofloxacin lactate with deltalambda = 190 nm in a B-R buffer medium of pH 2.87 were measured, and the partial least squares (PLS) method was applied to the quantitative resolution of the seriously overlapped fluorimetric spectra of these compounds. The linear ranges for norfloxacin, lomefloxacin chlorhydric acid, and levofloxacin lactate are 0.016-0.40 microg x mL(-1), 0.01-0.336 microg x mL(-1) and 0.01-0.336 microg x mL(-1), respectively. The limits of detection are 0.012 6 microg x mL(-1) for norfloxacin, 0.006 microg x mL(-1) for lomefloxacin chlorhydric acid, and 0.007 2 microg x mL(-1) for levofloxacin lactate. The analytical results by PLS were compared with principal components regression (PCR) and classical least squares (CLS), and this method was applied to the determination of these three compounds in eel samples with satisfactory results.

[Simultaneous synchronous spectrofluorimetric determination of vitamin B1, B2 and B6 by PARAFAC].

In the present study, a synchronous spectronfluorimetric method has been applied to the simultaneous determination of vitamin B1, B2 and B6. However, their spectra are overlapped so it is difficult to determine them individually. The parallel factor analysis (PARAFAC) was applied to the resolution of the overlapped spectra of mixtures of vitamin B1, B2 and B6. The delta wavelength range used was from 20 to 120 nm, and the excitation wavelength range was selected from 200 to 500 nm. From the measured fluorescence data a four-factor PARAFAC model was established, and was applied to the determination of a set of synthetic validation samples and some commercial samples with satisfactory results. This work shows that PARAFAC method is a powerful chemometric tool to the determination of mixtures of vitamin Bl, B2 and B6.

[Simultaneous determination of phenol and aniline in waste water by absorbance ratio derivative method].

A method of simultaneous determination of phenol and aniline in waste water by absorbance ratio derivative is reported in this paper. The sample, with which the pretreatment steps such as extraction, distillation, color development, and acid addition were not needed, was directly determined by the proposed method. Several synthetic samples of phenol and aniline and some real samples of waste water were determined by the method and satisfactory results were obtained. Under the optimal experimental conditions, the linear ranges of determination are 1.01-24.24 mg x L(-1) for phenol and 1.01-24.29 mg x L(-1) for aniline. And the limits of detection are 0.097 mg x L(-1) for phenol and 0.685 mg x L(-1) for aniline. For synthetic mixtures, the relative standard derivations (RSD) are less than 2.60% for both phenol and aniline, and the recovery is in the range of 95%-104%, but for real water samples the recovery is in the range of 91%-108%. The proposed method features high sensitivity and rapid resolution.