Computational Formulas for Total Relative Standard Deviations of CombinedGravimetric-Analytic Determinations

摘要

This report considered the sources of variability in each of severaldeterminations at the limits of quantitation of the aerosol gravimetric procedure. In an analytical gravimetric procedure, the difference between the presampling and postsampling weight of a filter is used to determine the mass of aerosol collected. The primary question is if the weight of the sample collected corresponds to the limit of quantitation of the gravimetric determination, then what is the magnitude of error for subsequent determinations, for example, of extractables. Using available data, the relative standard deviations for the determinations of the different components of the measurement processes are determined. These values can then be used in the formulas presented here to calculate the total relative standard deviations of the determinations, which can then be compared to target relative standard deviations, such as the assessment of accuracy. The authors present applications for collecting total aerosol on filters, followed by the analysis for solvent extractable material and polycyclic aromatic hydrocarbons.