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Strategies for detection of melamine in milk products

Strategies for detection of melamine in milk products. Xin Wu Literature Seminar 05/03/2010. Objective. Compare two methods to detect of melamine in milk products. Melamine. 2,4,6-triamino-s-triazine, MM In manufacture of: Plastics, Flame retardant Fertilizer Toxicity

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Strategies for detection of melamine in milk products

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  1. Strategies for detection of melamine in milk products Xin Wu Literature Seminar 05/03/2010

  2. Objective • Compare two methods to detect of melamine in milk products.

  3. Melamine • 2,4,6-triamino-s-triazine, MM • In manufacture of: • Plastics, • Flame retardant • Fertilizer • Toxicity • Acute toxicity • Chronic toxicity • Contaminants in many kinds of food http://www.toothpastefordinner.com/archives/2008/Dec/

  4. Summary of the detection methods Nitrogen methods Other methods

  5. Kjeldahl method • Degradation: Protein + H2SO4 → (NH4)2SO4(aq) + CO2(g) + SO2(g) + H2O(g) • Liberation of ammonia: (NH4)2SO4(aq) + 2NaOH → Na2SO4(aq) + 2H2O(l) + 2NH3(g) • Capture of ammonia: B(OH)3 + H2O + NH3 → NH4+ + B(OH)4– • Back-titration: B(OH)3 + H2O + Na2CO3 → NaHCO3(aq) + NaB(OH)4(aq) + CO2(g) + H2O

  6. Paper I Residue analysis of melamine in milk Products by micellar electrokinetic capillary chromatography with amperometric detection Jinyan Wang, Lianmei Jiang, Qingcui Chu , Jiannong Ye Food Chemistry 121 (2010) 215–219

  7. Capillary electrophoresis (CE) • Separate ionic species by their charge and mass. • UV or fluorescence detection • Advantages of CE over HPLC

  8. Micellar electrokinetic chromatography • Modification of capillary electrophoresis • Sample separated between micelles and buffer • C(Surfactant) >CMC • in open capillaries under alkaline conditions • Sodium dodecyl sulfate (SDS) Shegeru,Japan Chemical Journal 8:291-301

  9. Materials and Preparation • laboratory-built CE–AD system • MM ; Milk and infant formula milk powder samples; running buffer (8 mmol/L SDS/20 mmol/L H3BO3–Na2B4O7 solution) • Weighed-Extracted by ultrasonic bath-filtered-CEAD system

  10. Effect of the potential applied to the working electrode 1 Above 750 mV, oxidation current increased rapidly with applied potential. 2 Above 1200 mV, unstable baseline 3 1150mV is best choice

  11. Effects of the pH value 1 pH range 7.4-9.2 2 MM always overlapped with the unknown compound peak in real samples 3 pH is optimum pH

  12. Effects of SDS 1 at a fixed pH value 7.4 2 longer retention time with increased concentration of SDS 3 8 mmol/L SDS is optimum concentratioin

  13. Electropherograms

  14. Recovery of samples

  15. Conclusion • A new method of MECC-AD to residue analysis of melamine • For the real world sample • Run time is 9 min • Good recoveries ranging from 83.3% to 105.5% of MM were determined • Practical method with sample preconcentration

  16. Paper II A sensitive and validated method for determination of melamine residue in liquid milk by reversed phase high-performance liquid Chromatography with solid-phase extraction Hanwen Sun, Lixin Wang, Lianfeng Ai, Shuxuan Liang, Hong Wu Food Control 21 (2010) 686–691

  17. HPLC • separate, identify, and quantify compounds based on their idiosyncratic polarities and interactions with the column's stationary phase • A pump propel the mobile phase and analyte through densely packed column • Widely used • Various types of HPLC http://en.wikipedia.org/wiki/File:Hplc.JPG

  18. solid-phase extraction (SPE) • Concentrate and purify samples for analysis • Used to separate analytes from a variety of matrices: (1) blood (2) animal tissue (3) water etc. • Mobile phase (liquid and analyte); Stationary Phase (solid) • Silica

  19. Materials and Methods • Cleanert PCX-SPE cartridges (3 mL/60 mg), LC–MS/MS (Thermo Electron Corp., San Jose, CA, USA), an SeQuant ZIC HILIC column. • Sodium n-heptanesulfonate, acetonitrile, melamine, 1% trichloroacetic acid, 2.2% lead acetate solution, liquid milk sample • Confirmation by LC-MS/MS, Sample extraction and clean-up, HPLC analysis,

  20. The effects of pH pH =2.7 is the optimum value

  21. The effects of the ratio (v/v) between 10 mM sodium n-heptanesulfate (pH 2.7) and acetonitrile retention time of melamine shorted with the decrease of ratio value.

  22. The LOD and recovery of sample

  23. Conclusion • A new method of RP-HPLC-SPE to residue analysis of melamine • Real world sample • Run time is 10 min • Good recoveries ranging from 85.5–99.3%of MM were determined

  24. Comparison of the two methods

  25. Acknowledgements • Professor Kermit K. Murray • Murray Research Group • Audience

  26. Any questions?

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