The task of characterizing fine and ultrafine particulate matteremitted by vehicular traffic and industry draws upon not onlythe chemical composition of particulates, but also their sizedependence. However, conducting measurements of particulatesin the sub-micrometer range is no easy undertaking.The aim of this project is to develop a method whereby thecomposition of nanoparticles in correlation with their size isdetermined online directly in the air stream.

Method

Researchers are engaged in developing a method ofperforming chemical analysis of particulates on the basisof laser-induced breakdown spectroscopy. This methodinvolves analyzing single particles directly in the air stream,an approach that also permits rapid online characterization.Combining the method with particle technology makes itpossible to apply it to nanoscale particles. Placing an electrostaticclassifier upstream restricts the analysis to particulatesof a certain size, opening up the possibility of performingchemical analyses of defined particulate size classes.

Result

Researchers in this project performed size-resolved analyses ofnanoscale particles. The system can be calibrated to absoluteand relative concentrations of substances, for example toanalyze mixtures of substances or composite particles. Theresponse to changes in particulate composition is elicitedwithin a matter of seconds. Detection of single particles canbe achieved down to the 100 nm region.

Applications

Examinations of industrial processes have shown that thecomposition of particulates varies widely as a function of theirsize, and is characteristic of the specific process giving rise totheir emission. This finding permits process »fingerprints« tobe established, which in turn permit a classification particulatedto their sources of emission. The system’s rapid flagging ofchanging particulate composition means that it is also suitablefor online process control. This opens up potential for applicationssuch as examining the composition of nanoparticlesdirectly within a manufacturing process. The method can alsobe universally applied in other areas of industry that involveprocess dusts.