A simple method for determination of total water in PM1 on quartz fiber filters

Abstract

A method is proposed for applying the coulometric Karl-Fischer titration in analyzing the water content of submicron ambient particles (PM1) collected on quartz fiber filters of the most commonly used size (Ø47mm). The developed and validated method was applied to determine the water content of 24-h PM1 samples from two urban sites, one located in Warsaw and the other one in Zabrze, Poland.In some circumstances a number of analyses of particulate matter (PM) (e.g. for mass closure) are performed on the same PM sample, and some of them (e.g. those for carbon) imply application of quartz fiber filters. However, the hygroscopicity of quartz fiber filters interferes with determination of water content of PM sampled onto such filters.The water content of clean quartz fiber filters is high compared to water content of PM1 samples and differs from filter to filter significantly. Therefore, in order to determine water content of a PM1 sample on a quartz filter correctly one must know the water content of this particular filter. The proposed method is simple and allows for avoiding the artefacts related to water bound to filters. The estimated error of a single measurement in the proposed method is 4–17%, the detection limit is 27μg.The water content of 24-h samples of PM1 from the two urban sites in Poland was between 0.3 and 68%; in average it was 19% in Warsaw and 20% in Zabrze. Both the ambient concentrations and the difference between seasonal concentrations of PM1 bound water were higher in Zabrze.