Study of the uniformity of aerosol filters by scanning MA‐XRF

Abstract

Energy-dispersive X-ray fluorescence (XRF) is an attractive analytical method to determine the level of air pollution by heavy metals. The concentration of the filter in ng/cm 2 is obtained by direct comparison of the net characteristic line intensity of an element with that of a thin film standard. As the sampled area on the filter and the area of the standard are larger than the area analysed by the instrument, the distribution of the elements on the surface of both samples and standards have to be sufficiently uniform. If this is not the case, biased concentration estimates are obtained. Two scanning macro-XRF setups with a beam diameter of~0.5 mm were used to investigate the distribution of elements in (1) commercially available (Micromatter) standards, (2) in-house quartz filter standards obtained with an aerosol generator and (3) particulate matter (PM 10 ) collected on quartz filters by a Leckel SEQ 47/50 sampler. The uniformity of the Micromatter standards was better than 2%. At least some in-house standards showed a concave distribution with less material at the edges. The maximum bias introduced by this is less than 5%. Because of the limited sensitivity of scanning XRF compared with conventional XRF, the distribution of only a few common elements like Ca and Fe could be determined reliably in aerosol filters. The distribution of some heavy elements could only be measured in filters sampled in polluted regions. In general, the loading of particulate matter over the filters was uniform.

Elemental characterization and source identification of the near‐road PM2.5 using EDXRF in Chengdu, China

“…Correlation coefficients ( R 2 ) of each element were all higher than 0.98, manifesting the linearity of calibration curves. Because samples were considered as thin films, there were no matrix effects, and the relation between concentration and counts was linear . The limits of detection (LOD) for the EDXRF method is the minimum detectable concentration of elements that can be statistically discriminated from the background.…”

“…Because samples were considered as thin films, there were no matrix effects, and the relation between concentration and counts was linear. [16] The limits of detection (LOD) for the EDXRF method is the minimum detectable concentration of elements that can be statistically discriminated from the background. It is calculated by the a (from calibration curve) plus three standard deviation of y-residuals, S y/x , [17] and the results are also given in Table 3.…”

Atomic Spectrometry Update – a review of advances in environmental analysis

“…The production of certified reference filters is now planned. A sensitive scanning XRF system with a beam resolution of ~0.5 mm enabled 20 the spatial distribution of various elements across the surface of air filters to be examined. Application to commercially available Micromatter filter standards, widely used by XRFS laboratories that undertake air filter analysis, demonstrated that the distributions of elements were uniform to within 2%.…”

Preparation of standard materials of aerosol particles for X‐ray fluorescence analysis using a small chamber sampling unit

“…On the other hand, for accurate XRF analysis, preparation of calibrating standard material that has similar elemental composition to actual aerosols is essential because XRF intensities of analyte are absorbed or enhanced by sample matrix or coexisting elements. Several preparation methods of standard material for the quantitative analysis of aerosol samples have been reported, such as microdroplet of aqueous solution, coprecipitation by diethyldithiocarbamate, nebulizing of aqueous solution, use of thin film reference materials, an aerosol generator, and a small chamber sampling . Among these methods, the microdroplet of aqueous solution is simplest technique for preparation of the aerosol standard material.…”