Analysis of trace amounts of adulterants found in powders/supplements utilizing Raman spectroscopy coupled to direct analyte-probed nanoextraction-nanospray ionization-mass spectrometry

Abstract

In the United States, all food products have to be regulated to inform the consumers of the ingredients contained within. Some ingredients are not included on the label and yet are still found in the products. Presented is a Raman imaging technique for rapid, nondestructive, and spatially relevant localization of adulterants in powders. Raman spectroscopy followed by direct analyte-probed nanoextraction coupled to nanospray ionization-mass spectrometry allows rapid determination of the presence of each adulterant, leading to positive identifications such as melamine. The location and identification of these trace particles can then be extracted using a nanomanipulator. The nanomanipulation technique uses a solvent filled capillary tip which can be positioned on the particle of interest. Direct mass spectrometric analysis via nanospray of the particulate of interest eliminates time consuming chromatographic techniques prior to mass spectrometry analysis. This coupled technique combines rapid Raman spectroscopy techniques with direct mass spectrometry to confirm the presence of an adulterant. This technique was applied to an FDA supplied test sample, in which sibutramine, phenolphthalein, and melamine were confirmed to be present.