Application Note

High-throughput melamine detection with Beacon Analytical Systems Melamine Plate Kit

  • Quality assurance screening solution for the detection of melamine contamination
  • Maximum throughput with minimum manual plate handling
  • Complete data analysis with SoftMax Pro GxP Software

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The organic base melamine is used to make a number of products, including plastics, flame retardants, pigments, and fertilizers. The practice of adding melamine to animal feed and foods for human consumption in order to increase the apparent protein content has recently been reported. Because melamine contamination can cause serious illness or death in animals and humans, there is increased interest in identifying methods for detecting melamine contamination in a variety of food products. In this application note, the Melamine Plate Kit from Beacon Analytical Systems is introduced and validated.

The Beacon Melamine Plate Kit is a competitive enzyme-linked immunosorbent assay (ELISA) for the quantitative analysis of melamine in contaminated samples. A variety of sample types, including dairy products, wheat gluten, and wet and dry pet foods, may be assayed using this kit. Melamine is extracted from a sample by blending or shaking with extraction solution. Melamine HRP conjugate, sample extract, and calibrators are then pipetted into test wells coated with melamine antibody. After a 30-minute incubation, wells are washed to remove unbound melamine, and substrate is added to wells. The reaction is stopped after 30 minutes, and the absorbance of the wells is measured using an absorbance microplate reader. The melamine concentrations of test samples are interpolated from a melamine standard curve.

Absorbance microplate readers from Molecular Devices are used to detect the absorbance in the melamine assay. Molecular Devices AquaMax® 4000 Microplate Washer aspirates and dispenses all microplate wells simultaneously for rapid completion of the required wash steps. Data collection and analysis are performed using a melamine ELISA preconfigured protocol in SoftMax® Pro GxP Software, an industrystandard analysis software for FDA 21 CFR Part 11 compliance.



The following test procedure was used:1


Optical density (OD) values were used to construct a standard curve. Calibrators were plotted as OD values of the calibrators (y-axis) versus the log of the calibrator concentrations (x-axis). Sample melamine content could then be interpolated from the standard curve. Samples with OD values greater than the lowest calibrator or less than the highest calibrator must be reported as < 20 ppb or > 500 ppb, respectively.

Figure 1 shows the melamine standard curve plotted as described above, with a 4-parameter curve fit. Figure 2 shows the melamine standards plotted using a semi-log curve fit. The 4-parameter curve typically gives a better fit at the high and low ends of the standard curve and is preferable.

Figure 1. Melamine standard curve with 4-parameter fit. Melamine standards at 20, 100, and 500 ppb plotted as optical density of calibrators (OD) versus the log of the calibrator concentration. A 4-parameter curve fit was used. r2 = 1.000.

Figure 2. Melamine standard curve with semi-log curve fit. Melamine standards at 20, 100, and 500 ppb plotted as optical density of calibrators (OD) versus the log of the calibrator concentration. Here, a semi-log curve fit was used. r2 = 0.994.

Table 1 summarizes the Melamine Plate Kit Calibrator data. Excellent CVs of less than 5% were observed using the test procedure outlined in the product insert, and the AquaMax® 4000 microplate washer for the required wash steps.

Calibrator (ppb)
Average OD
Std Dev

Table 1. Melamine Plate Kit data summary. Average OD, standard deviation, and %CVs were calculated by SoftMax Pro Software. Standards were run in triplicate.


The Melamine Plate Kit from Beacon Analytical Systems, together with SpectraMax, VersaMax, VMax, and EMax Microplate Readers from Molecular Devices, offer a quality assurance screening solution for the detection of melamine contamination in food products such as milk, milk powder, yogurt, wheat gluten, and moist and dry pet food. The AquaMax 4000 Microplate Washer from Molecular Devices enables automation of the ELISA wash steps for excellent reproducibility and can be integrated with the StakMax® Microplate Handling System for increased throughput. Users may also configure the StakMax system with SpectraMax and VersaMax microplate readers in order to minimize manual plate handling. Complete data analysis is provided by SoftMax Pro GxP Software, an industry-standard analysis software for FDA 21 CFR Part 11 compliance.


  1. Melamine Plate Kit Instructional Booklet (Beacon Analytical Systems)

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