Slide 1What Is Melamine?More InformationAnalytical ProblemChoice of Technique: HPLC/UVOther Techniques Can be UsedInstrumentalProcedureData AnalysisExample ResultConclusionReferenceDETECTION OF MELAMINE IN MILKNai-Yuan LiuChem 410112/13/2011What Is Melamine?IUPAC name:1,3,5-Triazine-2,4,6-triamineUses: a very durable thermosetting plastic used in Formica, and melamine foam, a polymeric cleaning product.High nitrogen content: contains 66% nitogen by mass Outbreak in China, 2008:A company induce melamine into milk causing death of several infants.More Information According to WHO, the tolerable daily intake (TDI) of melamine is 0.2:mg per kg of body mass.According to the regulation in China, the amount lower than 2.5ppm in milk product is permitted.Ingesting excessive melamine leads to kidney lithiasis and makes it more possible to have malignant tumor inside kidney.High nitrogen content sometimes misleads the detection of protein in food product by the commonly used standard test.Analytical ProblemHypothesis:Company X induce melamine in their milk product and its amount exceeds the permitted standard.Importance of solving problem:Finding an easy, efficient and reproductive way to be a good food control process.Choice of Technique: HPLC/UVGood reproductivityNot labor intensiveEfficientCheapLow detection limit Simple method for preparing liquid milkOther Techniques Can be UsedAlternative method Advantage DisadvantageCE fast, high N, good LOD, sensitivity, low sample volume, very small sample valueLow reproducibility, sample recovery ESl/MS Soft ionization, good LOD, high sensitivityMultiply charged ions, expensive GC/MS Adequate sensitivity, good stability, good reproductivityNeed dirvatization, multipled charge ions, expensive, labor intensiveFluorescence More sensitive than UV-visUndetectable, need reagentInstrumentalDionex UltiMate® 3000 HPLC system (1200 USD): consisted of an HPG-3400A pump, WPS-3000TSL autosampler, TCC-3000 thermostated column compartment, and VWD-3400RS UV-VIS detector.HPLC:Chromatographic conditionsWCX-1 MethodGuard column Acclaim Mixed WCX-1, 5 μm, 4.3 × 10 mmAnalytical column Acclaim Mixed-Mode WCX-1, 5 μm, 4.6 × 250 mmColumn temp. 30 °CMobile phase NH4Ac buffer (10 mM, pH 4.3)/CH3CN (8:2, v/v)Flow rate 1.0 mL/minInject vol. 20 μLUV detection Absorbance at 240 nmMethod limit detection 0.028 μg/mLProcedureMeasure approximately 10mL of Samples into 15-mL centrifuge tubes, dilute it with 1 mL dilute HAc (3%, v/v), and store it at 4 °C for at least 30 min. Prepare spiked samples adding 40 μL of the stock standard solution of melamine to the 15-mL centrifuge tubes together with the measured sample, and then following the step above.Run both samples and spiked samples through UV-VIS UltiMate® 3000 HPLC system.Detect at 240nm.Data AnalysisCompare the samples to spiked sample results to determine the melamine peak.Calculate the area of the peak to determine the amount of melamine.Compare the amount of melamine in milk samples to the permitted amount.Example ResultFigure 1. Comparison between samples and spike samples. Upper is the sample and lower line is the spiked sample.Figure 2. Samples containing melamine. Upper line is for sample A. Lower line is for sample BDetected (μg/mL)Sample A 1.8Sample B 22ConclusionQuantitative detection of melamine can be done fast and easy by using HPLC/UV.This method can be commonly used as a standard test of melamine to avoid deadly milk product goes into market.ReferenceA Fast Method for Determination of Melamine in Liquid Milk and Milk Powder by HPLC With UV Detection by Lang Li, Ji Luo, Qun Xu, Jeff Rohrer, and Scott LeffertsA rapid, acetonitrile-free, HPLC method for determination of melamine in infant formula Gopalakrishnan Venkatasami, John R. Sowa Jr. ∗Department of Chemistry and Biochemistry, Seton Hall UniversityRapid Determination of Melamine in Liquid Milk and Milk Powder by HPLC on the Acclaim Mixed-Mode WCX-1 Column with UV DetectionDetermination of Melamine in Food by SPE and CZE with UV Detection, Liang Meng, Guijun Shen, Xiaolan Hou, Lili Wang, College of Environmental and Chemical Engineering, Dalian University, 116622 Dalian, People’s Republic of ChinaDetection of Melamine in Milk Products by Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry Shuiping Yang, JianhuaDing, Jian Zheng, Bin Hu, Jianqiang Li, Huanwen, Chen, Zhiquan, Zhou, and Xiaolin
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