The Novel Methods Of Health Laboratory Technology For Melamine And Nitrite

Melamine and nitrite are all the matter containing nitrogen element, and the important hygienic detection items at present. The former is used mainly as chemical industry material. It does not be permit to used as food additives and feedingstuff even now because its level of nitrogen (66% by mass, m:m) is higher more than the amino acids by 3-4 times, resulting in the failure of kidney and death. But melamine was illegally used in recent years due to that it can increase the protein content falsely, and threatening greatly to the health. Therefore, it is practical importance to study methods of hygienic detection of melamine. While the widely existed nitrite could be turned to N-nitrosamine in the human body, which is strong carcinogen. It was scientific researches on new methods of the hygienic detection of melamine and nitrite in this paper.Part 1, the headways trend and research statuses were summarized briefly about melamine and nitrite respectively. The novel ideas on the health laboratory technologies for melamine and nitrite in scientific researches were developed.Part 2, the interactions of melamine with ethanol were reviewed by the fluorescence spectroscopy method and one by Resonance Scattering Spectroscopy(RSS) in aqueous solution.â‘ The fluorescence quenching mechanism of ethanol was investigated after adding melamine, and apparent binding constant K was measured by spectrofluorometric method. Thermodynamic parameters obtained from measured data at different temperatures showed the binding force of melamine and ethanol.â‘¡The binding between melamine and ethanol had been investigated by RSS. The effort types of fluorescence quenching mechanism were analyzed firstly by RSS on the basis of the fluorescence quenching mechanism theory. Results were consistent with each other.Part 3, novel spectrofluorometric methods were developed for the determination of melamine.â‘ A novel spectrofluorometric method was proposed based on the formation of ion-association complex between melamine and formaldehyde and benzoinum in pH3.3 Britton-Robinson (BR) buffer solution, resulting in the enhancement of fluorescence intensity. It was found that the enhanced intensity was propotional to the concentration of melamine in the range of 8.0×10^-8～2.4×10^-5 mol/L, linear regression equation wasΔF=68.9c - 0.381(r = 0.9998) with the detection limit of 2.4×10^-8 mol/L. The average recoveries were 95.7%～110.0% with relative standard deviation(RSD) of 2.5%～4.1%. Satisfactory results were obtained for the determination of melamine in dairy sample.â‘¡The other one was proposed in the water phase based on fluorescence intensity enhancement after fluorescein sodium forms ion-association complex with melamine. The reaction mechanism studied applying the influence of the acid effect on the species distribution. It was found that the enhanced intensity was propotional to the concentration of melamine in the range of 4.8×10^-3～90.0μg/mL and 1.6×10^-2～280.0μg/mL respectively, linear regression equation wereΔF=2660.3ρ+ 36.67(r=0.9992),ΔF=768.92ρ+ 160.66(r =0.9996)with the detection limits of 1.4 ng/mL, 5.0 ng/mL respectively. The optimum conditions of spectrofluorometric methods were investigated. It showed that the method was fast, convenient and accurate.Part 4, two topics were studied on the determination of NO₂^- and inhibiting mechanism of diallyl disulfide(DADS) based on spectrofluorometric method. The nitrosation reaction of NO₂^- (carcinogen) and acridine red (AR) could make the system of fluorescence intensity decreased, while DADS could inhibit part of nitrosation reaction and quenching of the system of fluorescence in the sulphuric acid medium. Novel spectrofluorometric methods were constructed to assay NO₂^- by synchronous fluorescence, three-dimensional fluorescence, resonance fluorescence firstly in this paper. Compared with the direct fluorescent method, the new ones had higher sensitivity, lower detection limit and larger detection range and so on. Principal of the repression was expounded by applying with the results of fluorescence quenching of the system of AR-NO₂^-, then novel methods and theory evidence was supplied for studying the antitumous effect of DADS.