Mercury Determination in Certifiable Color Additives Using Thermal Decomposition Amalgamation and Atomic Absorption Spectrometric Analysis

Background Color additives requiring batch certification by the U.S. Food and Drug Administration (FDA) have Code of Federal Regulations (CFR) specification limits for certain elements and are usually analyzed by x-ray fluorescence spectrometry (XRF). However, sensitivity for Hg is too low in some color additives. Objective The thermal decomposition amalgamation-atomic absorption spectrometric (TDA-AAS) technique was investigated for providing quick and accurate determinations of Hg in certifiable color additives. Methods Tests were performed to optimize conditions and test reliability of Hg determinations at and below the CFR specification limit of 1 mg/kg. Results Sensitivity is much improved over XRF with limits of quantitation of 0.03 mg/kg for highly homogeneous color additives. Conclusions The TDA-AAS method can be used for determining Hg concentrations at and below the CFR specification limit. The technique is effective for all color additives, including those that are difficult to analyze by XRF, but less efficient for color additives that quickly deteriorate the catalyst. Regular quality checks using certified reference materials and in-house matrix-matched check standards are essential. Highlights The TDA-AAS method is applicable for use in routine color additive batch certification. Certain matrices (notably those that release nitrogen or sulfur oxides or halogens upon combustion) necessitate more frequent replacement of the catalyst and recalibration, impacting productivity. Color additives containing BaSO4, in color additive lakes, that are difficult to analyze by other techniques are well suited for TDA-AAS analysis.