Spatial inhomogeneity of metals in particulate matter on ambient air filters determined by LA-ICP-MS and comparison with acid digestion ICP-MS

Abstract

Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) has been used to examine the spatial distribution of metals in particulate matter on ambient air filters. The implications of the inhomogeneous distribution observed for the sub-sampling of such filters for multiple analyses have been discussed. It has been shown that large biases in measured values may occur unless the position and size of the sub-sample are chosen judiciously. Additionally, LA-ICP-MS has been compared against acid digestion ICP-MS as an alternative method for the determination of metals in particulate matter. It has been shown that the majority of variation in the LA-ICP-MS sensitivity accrues from small differences in the positioning of samples.

Quantitative sampling and analysis of trace elements in atmospheric aerosols: impactor characterization and Synchrotron-XRF mass calibration

“…In the case of the filter analysis, outliers due to sample inhomogeneity are rather improbable since the percentage of analyzed area from total sample area amounts to 12.5% (1/8 of the filter) and is thus significantly larger than for the RDI analysis. Since inhomogeneities in the distribution of the material on the filters are a function of the distance to the center, portions of the filter were taken like pieces of a round pie to avoid this influence (Brown et al, 2009).…”

Metals distribution on the surface of quartz fiber filters used for particulate matter collection

“…The literaturę data regarding the nature of PM and PM associated metal distribution over the fi lter surface show inconsistent results. Some authors document homogeneity in the surface distribution of PM-related metals (Moura et al 1987, Low et al 1990), while others argue for distributional heterogeneity, which applies not only to metals but also to non--metallic PM compounds, such as ions (Marrero et al 2005, EPA 2008, Brown et al 2009, Brown and Keates 2011. In most cases this heterogeneity is found between the samples collected on inner and outermost fragments of the fi lter (Anglov et al 1993, Steinhoff et al 2000.…”

Preparation of ashless cellulose paper standards for rapid determination of multi-element concentrations in airborne fine particulate matter using laser ablation inductively coupled plasma mass spectrometry

“…These standards need to overcome the problems of nonstoichiometric ablation, aerosol transport, atomization, ionization, and instrument signal dri during the analysis of PM 2.5 using LA-ICP-MS, which are still the main defects that hinder the accuracy and precision of this technology. [17][18][19] In recent years, multiple quantitative analysis methods have been reported, including external calibration with or without internal standardization, solution-based calibration, and isotope dilution. [20][21][22][23] In general, external calibration strategy using solid certied materials (CRMs) that match the composition of an actual sample is the most reliable quantitative analysis method for LA-ICP-MS.…”