Error analysis for sampling of slurries: volumetric errors

Abstract

The propagation of errors associated with the sampling of heterogeneous solutions consisting of small particles in a liquid media (e.g., slurries) is considered. Errors associated with uncertainties in the sample volume, the number of particles extracted in the sampling volume and the variation in the mass of the individual particles are considered in the analysis. A random Gaussian distribution for the error in the average mass of the particle and volume sampled is assumed. A relatively simple equation showing the relative standard deviation of the sampled mass is presented and examples of the graphs obtained are given. For samples containing large diameter particles, the errors resulting from the inability to pipette a fraction of a particle are dominant. In contrast, errors in the pipetted volume on particle size distribution are most significant for solutions containing small particles. The equations can be used with estimates of the particle size distribution to evaluate the extent of sample inhomogeneity. Alternatively, calculations can be used in making an a priori evaluation of the average particle radii, size distribution and sampling volume required to minimise sampling errors.