Rapid Limit Tests for Metal Impurities in Pharmaceutical Materials by X-ray Fluorescence Spectroscopy Using Wavelet Transform Filtering

摘要

ABSTRACT: We introduce a new method for analysis of X-raynfluorescence (XRF) spectra based on continuous wavelet trans-nform filters, and the method is applied to the determination ofntoxic metals in pharmaceutical materials using hand-held XRFnspectrometers. The method uses the continuous wavelet trans-nform to filter the signal and noise components of the spectrum.nWe present a limit test that compares the wavelet domain signal-nto-noise ratios at the energies of the elements of interest to annempirically determined signal-to-noise decision threshold. Thenlimit test is advantageous because it does not require the user to measure calibration samples prior to measurement, though systemnsuitability tests are still recommended. The limit test was evaluated in a collaborative study that involved five different hand-heldnXRF spectrometers used by multiple analysts in six separate laboratories across the United States. In total, more than 1200 mea-nsurements were performed. The detection limits estimated for arsenic, lead, mercury, and chromium were 8, 14, 20, and 150 μg/g,nrespectively.