Preparation of a PM2,5-like reference material in sufficient quantities for accurate monitoring of anions and cations in fine atmospheric dust

A reference material of a PM2,5-like atmospheric dust material has been prepared by using a newly developed method. About 500 g of dust material was obtained by accumulating material from five freeze-drying cycles of ice-kernels containing ultra-fine particles. After filling 150-mg portions of fine dust into vials under inert atmosphere, the reference material will undergo several tests according to ISO Guide 34 to eventually become a certified reference material. It is intended to certify values for the mass fraction of SO42-, NO3-, Cl- (anions) and Na+, K+, NH4+, Ca2+, Mg2+ (cations) in this material. A successful route for preparation of the candidate reference material is described alongside with two alternative approaches that were abandoned. The technical and physico-chemical problems were solved by applying a multi-step approach. First a PM10-like suspension spiked with the ions was allowed to stand for 72 h, next 90 % of the volume was siphoned off followed by drop-wise shock-freezing of the resulting suspension in liquid nitrogen. Finally freeze drying of the ice-kernels took place. Using this approach it was possible to produce a sufficient quantity of PM2,5-like material with appropriate characteristics. The failed approaches involved direct jet-milling of a PM10-like material and spray drying of a suspension of the PM10-like material spiked with the necessary salts (following sedimentation). The final candidate material approaches the EN12341-definition of a PM2,5-material containing the ions mentioned in Directive 2008/50/EC of the European Union. Sub-portions can be taken from the vials and subsequently analysed directly using the CEN/TR 16269:2011 method for anions and cations in PM2,5 collected on filters. For the production of a CRM, collection of sufficient quantities of homogeneous PM2,5-material on filters would be next to impossible due to the large variation in material properties induced from long sampling periods necessary from ambient air. The method described here is a relatively rapid means to obtain more than 100 g of material per freeze-drying cycle. With access to smaller freeze dryers amounts of 5 to 10 g per freeze drying cycle can be obtained. Access to such quantities of PM2,5-like material could potentially be useful for different kinds of experiments when performing research in this field.

CHAROUD-GOT Jean;  EMMA Giovanni;  SEGHERS John;  TUMBA-TSHILUMBA Marie-France;  SANTORO Anna;  HELD Andrea;  SNELL James;  EMTEBORG Hakan; 

2019-01-30

SPRINGER HEIDELBERG

JRC107334

1618-2642 (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC107334,   

10.1007/s00216-017-0670-6 (online),