R. M. Jacobs1 , P. T. Palmer2 , 1San Francisco District Lab, ORA, FDA, Alameda, CA, 2San Francisco State University, San Francisco, CA
Background: Energy dispersive x-ray fluorescence (EDXRF) technology to detect and quantify toxic elements has dramatically improved in the last 25 years. Over the last half decade portable EDXRF (PEDXRF) devices have emerged. These devices have impressive capabilities. In addition to being fully portable hand-held devices, their on-board functions have enabled them to accomplish an assortment of applications. The design of these devices has been focused on the non-scientific user. Some devices bear identification algorithms, the ability to display emission spectra, and the ability to quantify elements. Some are able to determine many toxic elements in ppm concentrations in foods. A Niton PEDXRF was used to evaluate a number of FDA samples (e.g., consumer complaint samples that caused injuries, samples of Asian patent medicines, dietary supplement ingredients both in field locations, e.g. Postal facilities and in the lab. Quantitative assessments of these products were conducted in the lab.
Methods:Samples that were chosen for evaluation were either ones from poisonings, ones that were Asian patent medicines with known additions of toxic elements, or samples where toxic elements were found by chance during the course of quantitative analysis by other techniques. One poisoning case involved dairy cows that had been accidentally poisoned with a chromate compound. These samples (cow hide) were obtained after the toxic substance had been identified. In field investigations, some samples, e.g., Asian patent medicines were initially tested through their packaging, e.g., blister packs. Other preparations, e.g., tablets and powders were placed in small testing vials equipped with a Mylar window and tested in "bulk mode". This mode yields several types of data outputs: algorithm based identification, the concentration of the element (when the sample is homogeneous), and the emission spectrum of the sample. Tests conducted in the lab were typically preceded by sample pulverization. The tests were conducted with a Niton XLi-728e. This model was equipped with dual radioisotopic sources, 109Cd and 241Am for target analyte excitation. Samples were typically excited for a 2 minute period using the 109Cd source. Typical target analytes for this mode were Cr, Fe, Pb, Hg, As, Se.
Results: 1. Examination of a consumer complaint sample involving a human poisoning from As in a food condiment accidentally contaminated with sodium arsenite, yielded nearly instantaneous identification of the presence of arsenic and comparable quantitative results by PEDXRF and ICP-MS, 244 mg/kg and 233 mg/kg, respectively. 2. An Ayurvedic medicine, Pushpadhanwa (a fertility medicine), was found to contain percent levels of Fe, Pb, and Hg. This product had been responsible for several serious injuries (e.g., spontaneous abortion, illnesses requiring hospitalization). While the lead content had been found by others, the product also contained undiscovered and equivalent amounts of mercury and iron. PEDXRF identified these ingredients almost instantaneously. 3. The analysis of an Ayurvedic medicine ingredient, Kapikachu powder, by PEDXRF and ICP-MS yielded highly similar results for arsenic, 203 mg/kg and 181mg/kg, respectively.4. Using the PEDXRF on a baby food sample reported to contain metallic mercury, the device quickly identified the "mercury" as mixture of aluminum and iron that was trapped in the glass. This finding averted undue concern regarding the safety of the product. 5. "Chromium Cow":While this turned out to be an on-farm accident, the identification of the causative agent took a couple of weeks. Examination of the exterior surface of the hide using the PEDXRF revealed, nearly instantaneously, extraordinary high amount of chromium was on the exterior surface compared to the very low levels normally encounter in tissue. The use of this device on the farm could have averted many of the suspicions of the identity and origin of the poison.
Conclusions:PEDXRF devices are able to rapidly identify and often quantify various ranges of toxic levels, i.e., from relatively low ppm levels to percent levels in foods and other sample types. These devices can often detect these elements through packaging and are ideal for field investigations. Laboratory use of the PEDXRF can allow much more rapid response to samples that may contain hazardous levels of toxic elements and therefore resolution of regulatory status of a sample. PEDXRF and laboratory grade EDXRFs could fill very important niches in FDA's inspectional and laboratory capabilities in detecting toxic elements in foods, Asian patent medicines, and other regulated products.