PM10 sampler deposited air particulates: ascertaining uniformity of sample on filter through rotated exposure to radiation

For reproducibility of analytical results of samples deposited on filters using PM₁₀ sampler, homogeneity of the sample on the filter is very important especially when the size of the X-ray beam for the analysis is less than the size of filter. It is against this background that the air particulate samples collected on using PM₁₀ samplers are analysed to determine the elemental concentrations. Each sample was divided into four quadrants and each was analysed under same conditions to determine if the particles were deposited uniformly over the filter. Each analysis was done using EDXRF technique. The spectrometer consists of four secondary targets, which are automatically switched to in sequence in analysing each sample. The concentration of various elements detected was determined using TURBOQUANT (a brand name for a SPECTRO method which is used for screening analysis). Sixteen elements were detected in every sample. Results show that there was less than 10% deviation in the concentrations in different quadrants. There were a few elements like Ba, Cs, etc., which have deviation greater than 20%. The concentrations of these latter elements were close to detection limits of the spectrometer. We conclude that the analytical result of particulate samples deposited on filters by the PM₁₀ sampler can be reliable in terms of the homogeneity of the deposition. For such analytes with low concentrations, it would be important that the sampling time be increased to allow for higher mass deposition on the filter. © 2006 Elsevier B.V. All rights reserved