| Abstract: With the improvement of living standards and changing consumer attitudes, people put a higher food safety requirement, after "Sanlu" problem milk powder causes some infants kidney stones disease, at home and abroad has aroused great concern of melamine in milk powder. Therefore, the establishment and improvement of the detection of melamine in the fast and easy way, has become an urgent need to resolve important issues.Melamine is an important heterocyclic organic chemical raw material, mainly used for condensation with+ aldehydes to produce melamine - formaldehyde resins to produce plastics, can also be used to make fertilizer. Melamine itself is less toxic, long-term or repeated exposure may affect kidney and bladder, leading to stone production, may further induce bladder cancer. Because of its high nitrogen content and odor and taste, often used by unscrupulous businessmen pretend food proteins.This paper selected dairy products - milk powder as the research object, after the samples extracted by cationic exchange solid-phase extraction column, detected melamine content in them by flow-inject Chemiluminescence.Details are as follows:Weigh 2 g (accurate to 0.0001 g) milk samples in 50 mL plastic centrifuge tube with stopper, added 15 mL1% trichloroacetic acid solution and 5 mL acetonitrile, 10 min after ultrasonic extraction, to 4000 r / min centrifugation 10 min. Filter the supernatant solution after 1% trichloroacetic acid wetting the filter paper, with 1% trichloroacetic acid solution to volume 25.00 mL, Pipette 5.00 mL filtrate, added 5.00 mL of water and purification liquid to be done after mixing. Extraction by cationic exchange solid phase extraction column, the extraction conditions are: using 3 mL of methanol, 3 mL distilled water of activation, Pipette 3.00mL be purified liquid to solid phase extraction column, using 3 mL of water and 3 mL of methanol elution Drained, with 6 mL5% ammoniated methanol elution, collecting eluate. The elution was dried with nitrogen at 50℃, then residuum was dissolved in hot double dished water, adjusted pH to 2.50 , after cooling to room temperature in 50 mL volumetric flask.Melamine was detected by Microwave Digestion - Flow Injection Chemiluminescence Method.The method in the selected digestion conditions,the optimal conditions of this chemiluminescence system were pH11.7 luminol solution 5.0×10-4mol/L,hydrogen peroxide solution 6.0×10-2mol/L,pH2.5 Cr+3 concentration 1.0×10-5mol/L. Under this condition standard curve was drawn. The result indicated that it presented linear relationship when the contents are in range of 5.0×10-7 mol/L～1.0×10-5 mol/L , related coefficient was 0.9991,the detection limit of melamine was5.2×10-9mol/L, RSD为2.3%.Melamine was detected by luminal- potassium permanganate chemiluminescence system. Optimum condition of this chemiluminescence system were pH12.5 luminol solution 6×10-4mol/L, potassium permanganate solution 1×10-5mol/L, pH2.5 Melamine test solution. Under this condition standard curve was drawn. The result indicated that it presented good linear relationship when the contents are in range of 1.0×10-11 mol/L～1.0×10-6 mol/L, related coefficient was 0.9991, detection limit was 3.2×10-13mol/L, RSD was1.1%.Melamine was detected by HPLC method. The condition is: 150mm×4.6mm stainless steel column, built-in C18, 5μm filler, mobile phase: phosphate buffer solution - acetonitrile (70 +30 by volume), flow rate: 1mL/min, column temperature: room temperature, UV Detector: wavelength 240nm. The detection limit was 3.71×10-7 mol/L.Thus, the sample preparation under the same conditions, using luminol- potassium permanganate chemiluminescence determination of melamine has wide linear range, high sensitivity, for the determination of melamine in milk powder with satisfactory results. |
PDF Full Text Request