Adhesive tape for spatially-resolved and sensitive detection of lead in dust using XRF

A method for rapidly and quantitatively measuring lead (Pb) in dust has been developed. While numerous wipes were tested, an adhesive wipe in the form of a portion of Painter’s tape (3x1.5 inches), has been found to effectively pick up dust due to its adhesive, and partnered with portable X-ray fluorescence (XRF), provides a rapid and sensitive measurement of Pb in dust, due to its flatness when folded. The tape can pick up 0.095 g of dust which is comparable to the amount of dust present in one square foot of a house that is vacuumed once a month (0.100 g). Dust in an area of 1 square foot was wiped up and a calibration curve was constructed by analyzing the folded tape on XRF (in ppm) versus the amount of Pb on the wipe that was determined by digestion and ICP-OES (in µg). The proposed test method has been validated with 63 field samples collected by 15 users and 2 XRF analysts. Validation was carried out by comparing the calibrated XRF results from the tape, to results of the same tape post digestion and ICP-OES analysis. In the validation study, when the threshold was set to 5 μg (current EPA action level for floors), a false positive rate (FPR) of 13% and a false negative rate (FNR) of 0% was obtained. For a threshold of 40 μg (current EPA action level for windowsills), a FPR of 3% and a FNR of 0% was obtained. For a threshold of 100 μg (current EPA action level for window troughs), a FPR of 5% and a FNR of 2% were obtained. When Pb dust-containing tape was sprayed with methyl ammonium bromide, a visual color response (green) was consistently obtained when Pb was present at levels above 100 µg. Thus, it was concluded that the color test could be used in the absence of an XRF on site, to identify gross Pb contamination. For lower Pb levels, Painter’s tape with XRF measurement will allow for spatially-resolved, rapid determination of Pb in dust on site, which has been a long-standing need.