Monochromatic 'high-definition' XRF is a highly robust tool for high-throughput lead screening of foods

Spices are well-known sources of harmful lead exposure, yet approved food testing methods, while sensitive and robust, are nevertheless slow, expensive, and labor-intensive. We addressed the need for a lead screening method in spices by leveraging monochromatic 'high-definition' X-ray fluorescence (mHD-XRF). By strictly applying FDA chemical method validation guidelines with 136 diverse spices collected at retail by 3 states over 13 years, we established mHD-XRF as an ideal screening tool. The level of detection was 0.044 ppm, which is ∼100-fold more sensitive than conventional XRF, and quantitation remained within 20% of 'gold-standard' values across >3 orders-of-magnitude. We set the screening threshold at 1.0 ppm, and encountered no false-negatives or false-positives in all 136 spices. FDA experts reviewed our level-2 single laboratory validation favorably, and the method was successfully added to our ISO/IEC-17025:2017 accreditation. Widespread operationalization of this method, especially at ports-of-entry, promises to increase spice surveillance by orders of magnitude.