AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
A New Personal Sampler for Measuring Inorganic Acid Mist and Gases: The Validation Test
CHIH-HSIANG CHIEN, Lin Shou, Alex Theodore, Chang-Yu Wu, Yu-Mei Hsu, Brian Birky, University of Florida
Abstract Number: 302 Working Group: Instrumentation and Methods
Abstract A novel personal sampler has been designed to overcome the inaccurate measurement of inorganic acid mist and gases in NIOSH Method 7903: a parallel impactor for classifying acid mist following ACGIH/ISO/CEN defined human respirable fraction, a porous membrane denuder for adsorbing acidic gases, and a filter pack to collect small particles penetrating the impactor and the denuder. The personal sampler was demonstrated to maintain particle collection efficiency greater than 99% for 4-hour sampling time as well as 4-hour gas collection efficiency over 95% for sulfur dioxide, hydrochloric acid, and nitric acid with a feed concentration of 10, 10, and 4 ppm, respectively. Additionally, the sampler successfully separated the collection of sulfur dioxide from that of sulfuric acid, thus eliminating the interference when the sulfur dioxide and sulfuric acid coexist.
To further validate the sampler’s performance, testing was carried out according to OSHA’s Validation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis. Under both low (22%) and high (64%) relative humidities, the sampler’s analyte recovery was above 99%. While particle growth due to the hygroscopicity of sulfuric acid shifts particle collection toward the impactor at high RH, the mass concentration of sulfuric acid was conserved for the combined impactor and filter collection. The storage stability of the sulfuric acid samples taken every 5 days showed that, for ambient storage, the overall standard error of the samples collected in 25 days was 5.76% with 95% confidence limit of 11.28%, while for refrigerated samples, the standard error was 4.96% and 95% confidence limit was 9.65%, indicating both storage methods impose no significant effect on the samples.
For aerosol collection, the parallel impactor has been further developed for the thoracic fraction. Further experiments will be carried out to verify whether the personal sampler’s particle collection efficiency follows the thoracic convention.