Novel Methods For The Health Laboratory Technology Of Melamine And Manganese

Melamine (MM) and manganese (Mn) are both important hygienic detection items. MM is an important nitrogen-heterocyclic organic compound, and responsible for kidney stones and other urinary diseases to infants. Mn is an essential microelement for human health, which may result in varying degrees of organ damage such as nervous, genital and respiratory system of human being by excessive ingestion; on the contrary, it is possible that the manganese-deficient associated with arteriosclerosis, retardation and skeletal deformities. Therefore, it is increasingly important to develop novel and simple methods for the determination of MM and Mn.In the chapter 1, the significance and headways trend of the health laboratory technologies for MM and Mn were summarized respectively; the determination methods of the health laboratory technologies for them were also introduced briefly in our work.In the chapter 2, three new spectral methods were presented for the determination of MM in dairy.①A novel spectrophotometric method was developed for the determination of MM based on the ion-association complex formation between MM and alizarin red (ALR) in aqueous micellar solution. Meanwhile, the ultraviolet-visible (UV-vis) spectrum characteristics of the complex of MM with ALR were investigated in sodium dodecylsulfate (SDS) micellar system. The spectras showed the maximum of the absorption peak of ALR shifted from 426 to 516nm due to the formation of the complex, and the absorption value (ΔA) in 516nm was positive correlated with the MM concentration. Furthermore, the stability and sensitivity of the method were remarkably enhanced by adding a certain amount of SDS. Beer′s law was obeyed in the MM concentration range of 1.9-25.0mg/L, and the apparent molar absorptivity coefficient of the complex was 6.9×103L·mol-1·cm-1. The established method was successfully applied to the determination of MM in liquid milk and milk powder. The recoveries were 94.5-104.8% and 95.5-100.4%, the relative standard deviations were between 1.6-2.2% and 1.7-2.6%, respectively. The possible mechanism of the complex was also investigated.②A novel fluorescence spectrometry was reported for determination of trace MM in dairy based on the inhibitory effect of MM on the decolorizing reaction of the uncatalytic oxidation of acridine red (AR) by potassium permanganate (PP) in sulfuric acid (SA) medium. The calibration graph was linear for MM concentrations of 2.1×10-4-1.6mg/L, and the detection limit was 61.5ng/L. MM was determined in diary samples by the proposed method after liquid-liquid and solid phase extraction, and the results correlated well with high-performance liquid chromatography. The possible mechanism of the reaction had also been investigated by UV spectra.③The present work reported a novel fluorescence spectrometry for determination of trace MM in dairy. The method was based on the inhibitory effect of MM on the decolorizing reaction of pyronine Y (PY) by potassium dichromate (PD) in sulfuric acid (SA) medium. Under optimal conditions, a calibration graph of 8.7×10-4-1.5mg/L and a detection limit of 2.6×10-4mg/L were obtained, respectively. The proposed method was simple, sensitive, selective and inexpensive. It had been applied to the determination of trace melamine in biscuit and milk samples with satisfactory results.In the chapter 3, two novel resonance light scattering (RLS) methods were presented for the determination of trace Mn in water.①A novel RLS method was developed for the determination of total Mn based on the self-aggregation reaction of the MnO2 product of the redox reactions between potassium permanganate (PP) and dimethyl sulfoxide (DMSO) in the Tris-HCl buffer solution of pH6.0. Under optimal study conditions, a good linear relationship existed between the intensity of RLS and Mn (Ⅶ) concentration (c =6.3×10-3-7.5×10-1μmol/L). The linear regression equation wasΔI=-217.3+114.7c (r=0.9991), and the detection limit was 1.9×10-3μmol/L, respectively. The present method was simple, specific and sensitive. It had been applied to the determination of total Mn in the environmental water samples with satisfactory results.②A novel RLS method was proposed for determination of trace Mn (Ⅱ) based on the ion-association complex formation between Mn (Ⅱ) and safranine T (ST) in Britton-Robinson (BR) buffer solution at pH10.0. Besides, the stability and sensitivity of the method were remarkably enhanced by adding a certain amount of cetylpyridinium bromide (CPB). Under optimized conditions, the enhanced RLS intensity (ΔI ) had a good linear relationship with the concentration of Mn (Ⅱ) (c) in the range of 3.6×10-5-1.1×10-1mmol/L. The linear regression equation ofΔI=8.4+3857.1c with a correlation coefficient of r=0.9980 and a detection limit of 1.1×10-5mmol/L were obtained, respectively. The proposed method had the advantage of simplicity, high sensitivity and low cost, which had been applied to the determination of trace amounts of Mn (Ⅱ) in bottled drinking water with satisfactory results.