As part of the public health investigation into elevated lead (Pb) levels in an apple cinnamon fruit puree, cinnamon was identified as the source of contamination. Cinnamon samples were tested by inductively coupled plasma mass spectrometry (ICP-MS) at the U.S. Food and Drug Administration's (FDA) Kansas City Human and Animal Food Laboratory and determined to contain elevated levels of Pb (>2000–5000 µg/g) and chromium (Cr) (>500–1200 µg/g). Total Pb and Cr concentrations alone could not determine the source of the contamination. To aid in the investigation of potential sources of the Pb and Cr contamination, e.g., particles from grinding equipment or addition of lead (II) chromate (PbCrO 4 ), further information was needed. The FDA's National Forensic Chemistry Center conducted additional analyses in which suspected lead (II) chromate particles were physically isolated and preconcentrated, then analyzed by Raman microspectroscopy. Once Raman spectra of the preconcentrated particles were obtained, the same particles were removed from the microscope slide and digested with nitric acid for ICP-MS analysis. The combination of the Raman spectral comparison to a lead (II) chromate reference standard and confirmation of Pb and Cr in the particles with 1:1 stoichiometry using ICP-MS identified lead (II) chromate as the contamination source. This confirmed that lead (II) chromate had been added to the cinnamon, suggesting intentional adulteration. Previous reports indicate that lead (II) chromate can be added to spices to enhance the color and/or increase the mass of the product. This paper demonstrates how combining two complimentary instrumental techniques was used to identify and quantify an inorganic compound in a possible case of economically motivated adulteration.
Kubachka et al. (Sun,) studied this question.