Lead Pb exposure assessment in dried blood spots using Total Reflection X-Ray Fluorescence TXRF

Abstract

Whole blood remains the most used biomarker for lead (Pb) biomonitoring, however, blood sampling has several limitations, including its invasive nature. Dried Blood Spots (DBS) have been applied as an alternative to traditional methods for decades, but there are gaps that have prevented them to be adopted in biomonitoring programs, such as their small sample volume. There are microanalytical techniques that require a low volume (<10 µL) to perform the analysis, such as Total Reflection X-Ray Fluorescence (TXRF), however, this approach has not been evaluated yet. This study aimed to validate and apply a method to assess Pb exposure using DBS samples and TXRF. First, we developed a method testing different parameters including digestion and extraction procedures, and the use of different internal standards. Next, we validated our method evaluating several validation parameters, and we compared our results with standardized guidelines. Finally, we applied our method with samples from two cohorts. The limits of detection and quantification of the method were 0.28 and 0.69 µg/dL, respectively. The overall precision and accuracy of the method were 14.88 % (9.92-19.14 %) and 111.14 % (97.03-129.70 %), respectively. The Bland-Altman plot indicated a good agreement between ICP-MS and TXRF, with a mean of differences of -0.02 µg/dL. These results demonstrate that TXRF is a good alternative to traditional methods for the analysis of Pb in DBS samples and it alleviates challenges such as the low volume of sample, analytical interferences, and sample throughput.