Adaptation of the BCR sequential extraction procedure for fractionation of potentially toxic elements in airborne particulate matter collected during routine air quality monitoring

The Community Bureau of Reference (BCR) four-step sequential extraction has been adapted for fractionation of potentially toxic elements (PTE) in simulant airborne particulate matter (APM) samples presented on 47 mm filter dynamics measurement system (FDMS) filters as used in routine air quality monitoring. Simulants were prepared from an urban soil reference material and from BCR CRM 701, which is certified for analytes extractable by the BCR procedure. Analysis was performed by inductively coupled plasma mass spectrometry using an Agilent 7700x instrument. Fractionation patterns similar to the full-scale protocol were obtained when test portions as small as 0.0625 g were extracted in 2–3 mL of reagents. However, changing the extraction vessel used was found to affect the outcome. This highlights the operational nature of sequential extraction procedures and the need carefully to evaluate the effects of procedural modifications. When the method developed was applied to blank FDMS filters, large amounts of Zn were detected, especially in step 3, the oxidisable fraction, and step 4, the residual fraction. Despite this, following blank-correction, fractionation patterns similar to certified values were obtained for BCR CRM 701, with overall recoveries (∑(steps 1–4)) of 84.2-113%. Given the increased awareness of public health risks associated with poor air quality, a sequential extraction procedure specifically designed for use with APM samples collected during routine air quality represents a valuable tool for use in source apportionment and to improve understanding of human exposure to PTE through inhalation.