Dithiothreitol-based oxidative potential for airborne particulate matter: an estimation of the associated uncertainty
2020
Molina, Carolina | Andrade, Catalina | Manzano, Carlos A. | Richard Toro, A. | Verma, Vishal | Leiva-Guzmán, Manuel A.
Oxidative stress is considered as one of the main mechanisms by which airborne particles produce adverse health effects. Several methods to estimate the oxidative potential (OP) of particulate matter (PM) have been proposed. Among them, the dithiothreitol (DTT) assay has gained popularity due to its simplicity and overall low implementation cost. Usually, the estimations of OPᴰᵀᵀ are based on n-replicates of a set of samples and their associated standard deviation. However, interlaboratory comparisons of OPᴰᵀᵀ can be difficult and lead to misinterpretations. This work presents an estimation of the total uncertainty for the OPᴰᵀᵀ measurement of PM₁₀ and PM₂.₅ samples collected in Santiago (Chile), based on recommendations by the Joint Committee for Guides in Metrology and Eurachem. The expanded uncertainty expressed as a percentage of the mass-normalized OPᴰᵀᵀ measurements was 18.0% and 16.3% for PM₁₀ and PM₂.₅ samples respectively. The dominating contributor to the total uncertainty was identified (i.e., DTT consumption rate, related to the regression and repeatability of experimental data), while the volumetric operations (i.e., pipettes) were also important. The results showed that, although the OP measured following the DTT assay has been successfully used to estimate the potential health impacts of airborne PM, uncertainty estimations must be considered before interpreting the results.
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