Simultaneous Extraction and Rapid Analysis by LC–MS-MS of Melamine and Cyanuric Acid Using New Kinetex Core-Shell Technology

The presence of both melamine and cyanuric acid in concentrations greater than 2 μg/mL results in the crystallization of the two compounds, forming the toxic, water-insoluble melamine cyanurate complex. This article describes a method for the simultaneous extraction of both compounds using one solid phase extraction sorbent, Strata® Melamine, followed by single injection LC–MS-MS analysis using Kinetex™ HILIC Core-Shell technology to quickly and accurately measure melamine and cyanuric acid in less than 1 min.

Experimental Conditions

Prior to solid phase extraction, protein precipitation of the sample was performed by adding 3 mL of ACN to the 1 mL of spiked baby formula. After vortexing the sample, the supernatant was collected for the SPE step.

Results and Discussion

The sample load onto the Strata® Melamine SPE cartridge consisted of 75% ACN, necessary to crash out proteins, which we found to be essential in achieving acceptable recoveries of cyanuric acid.

The combined protein precipitation and solid phase extraction of melamine and cyanuric acid out of baby formula yielded relative recoveries of 115% and 94.5% respectively. Acceptable coefficients of variation (CVs) for both compounds, 4.10 for cyanuric acid and 3.05 for melamine, were also achieved.

Complete separation and detection of melamine and cyanuric acid was achieved accurately and precisely in less than one min by LC–MS-MS using a Kinetex® HILIC core-shell technology column (See Figure 1). The MS ionization mode was initially set for negative ionization to facilitate the detection of cyanuric acid, but following elution of the cyanuric acid peak, the source must be switched to positive ionization mode in order to allow for detection of melamine.

Figure 1: LC–MS-MS chromatogram of melamine and cyanuric acid extracts from baby formula separated on Kinetex™ HILIC.

Conclusion

The extraction and chromatography method is well suited for the analysis of melamine and cyanuric acid in dairy samples, such as baby formula. Food safety testing often requires extremely fast turn around time between samples to allow proper action to be taken; Kinetex core-shell columns and a one-cartridge SPE method allow any lab the ability to implement fast LC solutions for melamine and cyanuric acid testing. Methods described are suitable for the extraction and analysis of both compounds in other food samples; however some sample pretreatment modifications may be required. The Kinetex HILIC 2.6 μm core shell product is applicable on any LC system, allowing ultra-high efficiency and fast separations in every lab.

For complete method details, request Technical Note TN-0021 from Phenomenex.

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