The Healthy Stuff Lab tests products and environmental media using two in-house analytical instruments, an X-ray Fluorescence (XRF) analyzer and a Fourier Transform Infrared Spectrometer (FTIR). We also employ several other test methods at third-party labs and in university research labs.
XRF and FTIR are widely used by academic researchers, product manufacturers and government regulators to screen consumer products for hazardous chemicals. Each test method has its own strengths and limitations.
Each report published by our lab includes a Method section specific to the study done for that report.
X-ray fluoresence spectroscopy
XRF Background Material
- Comparison of Testing of Plastics for Lead by X-ray Fluorescence and Traditional Nitric Acid Digestion/ GFAA After Muffle Furnace Combustion, November 8, 2008. Danielle Cappellini, B.Sc., MHA and Woodhall Stopford, MD, MSPH, Duke University School of Medicine.
From the Study: "Originally billed as a "screening" technique, these results suggest that in the range of concern, x-ray fluorescence can be used to determine accurately the presence of excessive levels of lead in plastic materials."
- Study of the Effectiveness, Precision, and Reliability of X-ray Fluorescence Spectrometry and Other Alternative Methods for Measuring Lead in Paint, August, 2009. U.S. Consumer Product Safety Commission
- Linking PBDEs in House Dust to Consumer Products using X-ray Fluorescence, Allen, Joeseph, et. al., Environmental Science and Technology April 30, 2008.
- Common Research Uses for XRF Technology - Summary or Detailed Review with Abstracts A summary of over 80 peer review research papers, from dozens of research areas, which utlized XRF testing as a core analytical method. XRF analyzers are usd by US Customs, FDA, EPA, DOE, & Consumer Agencies. Read more about the use of XRFs for compliance screening.
Quality Assurance/Product Variation - We routinely collect XRF readings from certified reference standards to verify accuracy. We also collect periodic repeat or duplicate scans. These include readings taken from a single location on one product to test repeatability and readings taken from different locations on the same sample to assess variability inherent in the sample.
Data Interpretation - We interpreted the results using the concentrations and uncertainties reported by the analyzer, together with visual examination of the spectra generated by the instrument. The analyzer reports concentrations of elements by analyzing the spectra using reference data for the elements it reports, and measuring the area under the curve in the spectrum. We visually examine a some of the collected spectra to confirm visual observation of key peaks matches the software's reporting.
XRF Testing Methodology
We use a High Definition X-Ray Fluorescence (HDXRF) analyzer manufactured by X-Ray Optical Systems (download XRF Factsheet). The HDXRF analyzer measures levels of chemical elements, such as lead, cadmium, chlorine, bromine, arsenic, mercury, tin, and antimony. The major benefit of HDXRF is that monochromatic excitation eliminates the X-ray scattering background under the fluorescence peaks, greatly enhancing detection performance. This analytical approach results in detection limits in the parts-per-million (ppm) range for many elements of interest in a variety of materials.
The elemental composition of the materials reveals the presence of potentially hazardous chemicals, such as metals, and also allows researchers to infer the possible presence of toxic chemicals or materials, including brominated, chlorinated, or phosphorus-based flame retardants and polyvinyl chloride (PVC). There are a number of chemicals of concern that cannot be detected by this technology.
The levels of lead, cadmium, chlorine, and other elements shown in this website are those reported by the HDXRF analyzer manufactured by X-Ray Operating Systems. Our testing methodology uses standards with known levels of certain elements to check the accuracy of the analyzer in one type of matrix material. However, the products we tested are made of many different types of materials, in some cases even within the same product. A multi-component or multi-layered sample may interfere with the analyzer's ability to quantify the elements accurately. When the component materials in a sample are not homogeneous, the test results may vary depending on the orientation between the object under test and the testing device.
Therefore, the levels we report provide a general indication of the levels in the products in order to guide consumers on product choices. More exhaustive testing with XRF, as well as laboratory testing, could provide more detailed findings on the levels of elements and associated compounds.
Fourier Transform Infrared Spectroscopy (FTIR)
The Healthy Stuff Lab uses a Nicolet iS5 FTIR spectrometer with a single-bounce diamond attenuated total reflection (ATR) accessory to analyze the composition of a wide variety of polymeric and natural materials. The method complements XRF because it identifies molecular structure rather than individual elements. Absorbance spectra are collected from 4000-500 cm-1 with 4 cm-1 resolution averaging 12-16 scans using Omnic software. No smoothing or atmospheric suppression is applied to the spectra.
We use a combination of visual inspection of the spectral data and match searching within FTIR libraries both purchased (c. 2008 Thermo Fisher Scientific) and obtained in-house. Omnic Specta software was used to help identify some multi-component samples. Regardless of the software, to determine a positive match we required visually apparent alignment of key peaks in the experimental spectrum with a known spectrum. Interpreting the data requires a trained spectroscopist to assess the closeness of matches to library and reference spectra.
The majority of samples we test with FTIR are polymeric materials or polymeric coatings, such as food can interior coatings and nonstick cooking pan coatings. In addition to identifying the main material (the "matrix") we can identify many intentionally added chemicals including plasticizers such as phthalates and alternatives, slip and mold release agents, certain antioxidants, phosphorus-based flame retardants, chlorinated organophosphate flame retardants, talc, carbon black, and calcium carbonate. In thermal paper cash register receipts, the method can detect bisphenol A, bisphenol S and alternative developers.
FTIR provides a rapid and low-cost analysis without extensive sample preparation. The main downside is a high limit of detection for additives. In a real-world flexible PVC item, for example, plasticizer levels must be at least approximately 1% by mass to be detected. Lower levels can be detected in certain cases.