A number of reports by various regulators, media, and watchdog groups have identified numerous face cream products containing percent levels of mercury that are far in excess of the FDA regulatory limit of 1 ppm.  The mercury is added to provide skin bleaching properties to the face cream, and poses a serious health risk to consumer through dermal exposure as well as inhalation of volatile forms of mercury in some of these products.  This study describes the development of several different XRF and TXRF methods for determination of mercury in several face cream products containing non-detectable to percent levels of mercury, as well as a critical evaluation of each method and comparison of results to those from the more widely accepted ICP-MS method.  For screening and identifying such products in the field, XRF is the method of choice as it involves direct analysis of the sample with analysis times on the order of one minute or less, and can readily detect the presence of mercury down to single ppm levels.  Although calibration of the XRF analyzer using authentic standards yielded results that compared well to those from ICP-MS for homogeneous products, the results were more variable for products containing small crystals or chunks of inorganic mercury salts.   For these products, more accurate quantification of mercury requires more time-consuming sample preparation with microwave digestion to provide a representative subsample for analysis, followed by either TXRF and ICP-MS analysis.  The TXRF method uses an internal standard and requires no additional calibration, and gave results that compared well to those from ICP-MS.  Although ICP-MS is often the method of choice for trace level determination of a variety of elements, it is the most expensive of all of these methods, has detection limits which are orders of magnitude lower than necessary for this application, involved the use of dilution factors on the order of 1,000,000, and gave erroneous results for two samples due to either cross contamination or carryover.  Moreover, the inadvertent analysis of samples containing high levels of mercury via ICP-MS may lead to contamination of this equipment which is often used for trace level analysis.  Given the prevalence of these products and their sale and use in third world countries, it is recommended that portable XRF be used to screen for such products and XRF or TXRF methods be used for accurate quantification of mercury in homogeneous and heterogeneous products, respectively.

Comparison of XRF, TXRF, and ICP-MS methods for determination of mercury in face cream

248th National Meeting (2014)

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