NMR-spectroscopy for nontargeted screening and simultaneous quantification of health-relevant compounds in foods: the example of melamine

Abstract

The recent melamine crisis in China has pointed out a serious deficiency in current food control systems, namely, they specifically focus on selected known compounds. This targeted approach allowed the presence of melamine in milk products to be overlooked for a considerable time. To avoid such crises in the future, we propose that nontargeted screening methods need to be developed and applied. To this end, NMR has an extraordinary potential that just started to be recognized and exploited. Our research shows that, from the very same set of spectra, (1)H NMR at 400 MHz can distinguish between melamine-contaminated and melamine-free infant formulas and can provide quantitative information by integration of individual lines after identification. For contaminated Chinese infant formulas or candy, identical results were obtained when comparing NMR with SPE-LC/MS/MS. NMR was found to be suitable for routine nontargeted and targeted analyses of foods, and its use will significantly increase food safety.

Figure 1

Comparison of melamine-contaminated Sanlu sample with the reference distribution of a collection of infant formulas (measurement in DMSO-d₆ at 400 MHz). The signal at 5.93 ppm derives from the NH₂-groups of melamine.

Figure 2

Upper panel: Comparison of melamine-contaminated Sanlu sample with the reference distribution of a collection of infant formulas (measurement in water at 400 MHz). Lower panel: Reference measurement of sucrose from the spectral library.