Is X-ray Fluorescence (XRF) an acceptable method for determining compliance?
XRF is an excellent tool for screening, however, the results should be carefully evaluated for false positives as well as false negatives. Obtaining accurate results using XRF on packaging can be very challenging because there are many variables that can affect the results, including sample matrix, sample thickness, sample homogeneity, chemical interferences, and instrumental errors. Positive results should be followed up with definitive testing by an accredited laboratory with demonstrated proficiency in testing the type of material. An effective quality assurance program for compliance screening may include XRF, but should also include a method demonstrated to completely digest the sample, followed by definitive testing such as inductively coupled plasma (ICP) analysis. Incomplete digestion of the sample will not provide a measure of total metals. ASTM recently released Method F 2617-08 for measuring cadmium, lead, and mercury in polymeric material using XRF.2 It is critical to note
