Development And Application Of Detection Methods For Melamine In Water And Sediment

Melamine is relatively stable in the environment and difficult to degradation in soil, sediment and water. Because of many kinds of ways of contaminated soils, sediments and water body, melamine can be transferred to the body of crop plants by means of root absorption, and lead to plant products have a small amount of melamine residue; it would bring a trace amounts of melamine to animal products if contaminated crops be used as raw materials, straw feed and forage grass.Because of the low content of melamine and complex of matrix composition of Environmental samples (such as soil, water, sediment, etc.), the sample preparation have become an indispensable step of melamine detection. Water, sediment and soil were selected as analysis object. The am of work is to study the effects of the solid-phase extraction (SPE), ultrasonic extraction (UE), high performance liquid chromatography (HPLC) with diode array detector (DAD), and set up two new methods of the determination of trace levels of melamine. The effects of pretreatment and Chromatographic detection technology were investigated to use single factor optimization method to determine the best conditions and evaluate the methods of analysis capability. New methods were successfully applied to the actual sample testing.1、A rapid, simple, economic, and efficient analytical method of trace concentrations of melamine in water were proposed by solid-phase extraction coupled to high performance liquid chromatography with diode array detector (SPE-HPLC-DAD). The qualitative effect of DAD could effectively reduce the false positive results. The work used CNW poly-Sery MCX column as the purification and enrichment of melamine, acetonitrile/water as mobile phase, Inertsil CN-3chromatographic column as chromatographic analysis column. Under the optimization of chromatographic conditions (wavelength was210nm, mobile phase was acetonitrile/water (5/95, v/v)), extraction conditions (pH6.0, kept flow velocity of solid phase extraction within1mL/min) and elution conditions (6mL5%amonium methanol), it have the most ideal extraction effect. The enrichment ratio was102, The limit of detection (S/N=3) and the limit of quantification (S/N=10) for melamine in soil were0.05μg/L and0.18μg/L. Based on the optimized conditions, the method has been successfully applied to the analysis of melamine in4kinds of actual water samples with satisfactory results.2、A novel method for the determination of melamine in sediment and soil was established, using ultrasonic-assisted extraction coupled with high performance liquid chromatography. The sample pretreatment conditions and the analytical chromatographic conditions were tested and optimized. The soil samples was extracted by ammonium methanol (5/95, v/v) with ultrasonic assistance for5min, followed by centrifugation and nitrogen blowing. Chromatographic separation was achieved by a GL Inertsil CN-3column using acetonitrile/water (5/95, v/v) as mobile phase, and the quantification was carried out by external standard method.A good linearity for melamine was obtained in the range of0.05～0.5mg/kg with a correlation coefficient of0.9999. The limit of detection (S/N=3) and the limit of quantification (S/N=10) for melamine in soil were0.01mg/kg and0.04mg/kg, respectively. The recovery for melamine ranged from95.9%to99.2%, with relative standard deviations (RSDs) of less than2%. The proposed method was shown to be rapid, sensitive, cheap and simple, and was applied to the analysis of melamine in several soil samples with satisfactory results.3、A miniature aquatic ecosystems was simulated to stady the dynamic change process of distribution and accumulation of melamine in water, sediment and accumulation and aquatic plants. Results show that after the melamine was entered into the water, one portion of it was adsorbed by the sediment, Tilapia mossambica, viviparid and aquatic plants, its concentration in the aqueous phase had a significant reduction in the first few days then slowly lower and stable. Due to the fast adsorption of melamine in the surface layer of sediment, the concentrations Continuous of melamine in the sediment rised quickly at first, but becomed smally after reaching adsorption-desorption dynamic balance. In the late test, because of the Continuous deposition of mossambica and viviparid’s metabolic waste and decomposition of Goldfish algae’s residue, the content of melamine in the sedimentary phase of tended to increase. The melamine showed a strong bioaccumulation effect in Goldfish algae, and the concent increasesed quickly at first and keep a rising trend during the entire test cycle. In addition, the microorganism in the system may be existed a certain degree of biodegradation of melamine.