Evaluation of HgI2 detectors for lead detection in paint

A laboratory study of HgI₂ spectrometers used for in-situ determination of lead on painted surfaces has been conducted. ¹⁰⁹Cd and ⁵⁷Co isotopes have been used to excite lead characteristic X-rays from samples. The energy resolution of HgI ₂ detectors in the energy region corresponding to lead K X-rays has been measured. An energy resolution of 880 eV (FWHM) for the 60 keV line from an ²⁴¹Am source has been obtained. Measurements using thin-film standards ranging from 0.5 mg Pb/cm² to 2 mg Pb/cm² have been conducted. Detection limits, accuracy, and precision of the measurements have been estimated. Based on a comparison of the results obtained with the performance of existing detector technology for hand-held X-ray lead analyzers, the HgI₂ detectors seem to be the best solution. A truly portable instrument for lead paint detection can be implemented by using HgI₂ detectors. Such an instrument can easily meet the requirement for a critical decision point of 1.0 mg Pb/cm², which is the regulatory limit for lead concentration in paints