[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.

[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.

[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.

[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.

[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.

[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.

[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.

[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.

[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.

[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.