A comparison of quartz filter collection versus electrostatic precipitation collection in e-cigarette aerosol samples
The determination of metals in E-cigarette aerosol has been routinely performed by collecting the aerosol on quartz fiber filter pads. The trapped aerosols are digested using acid dilution and analyzed using ICP-MS. The quartz filters have similar performance to standard Cambridge filters. The major problem with using quartz filters, is they contain detectable levels of many of the metals of interest and, even more problematic, the amount of metals varies between filters and filter lots. Each new lot of filters must be evaluated for background levels to establish method limit of detection (LOD). Even with background subtraction, the quartz filter method has elevated LODs and increased variability near the method LOD. In order to reduce background levels and improve method LOD we evaluated the use of an electrostatic precipitation (EP) unit to collect the aerosol. The EP unit has long been established in the collection of cigarette smoke (Health Canada Official Method T-109). In this study we validated the use of a 20-port EP system for the determination of metals in E-cigarette aerosol; focusing on trapping efficiency, analyte recovery, and background contamination. We will present findings that show a decrease in background contamination and an improvement in the detection limits of the EP method over the quartz filter method. The method LODs were lowered by an average of 72%. For example, Chromium for the filter collection method had an average method LOD of 103 ng/collection while the LOD for the EP method was 5 ng/collection. The EP system offers an additional improvement since each EP unit has the ability to collect up to 3.5 g of aerosol collected mass (ACM) while the filters are limited to maximum of ~ 0.8 grams of ACM. The ability to collect additional ACM significantly reduces method LOD on a per gram basis.