Filter and cassette mass instability in ascertaining the limit of detection of inhalable airborne particulates.
In the gravimetric assessment of workplace aerosols, there is an increasing need to confidently measure smaller and smaller collected masses. To do this, it is important to know both the limit of detection (LOD) and limit of quantification (LOQ) of the analysis performed, determined by the weighing imprecision of blank samples. Of particular current interest is the measurement of inhalable aerosols, as defined for many substances in the American Conference of Governmental Industrial Hygienists threshold limit values list. One popular method is the use of a filter contained within a small cassette, in which both are weighed. Earlier investigations of plastic and stainless steel cassettes showed that plastic cassettes are highly sensitive to changes in humidity. But one study also demonstrated that the resulting changes in mass could be largely corrected using field blanks. An investigation, therefore, was undertaken to determine the weighing imprecision of various cassette and filter assemblies, assuming blank corrections are made. Three types of filter (Teflon, glass fiber, and polyvinyl chloride) were investigated in combination with three types of cassette (plastic, nickel-plated plastic, and stainless steel). Results show that regardless of the substrate being used, sample masses equal to or higher than 0.19 and 0.65 mg can be confidently detected and quantified, respectively.
Paik
Samuel
S
Department of Environmental Health Sciences, School of Public Health, University of Michigan, 109 S. Observatory, Ann Arbor, MI 48109-2029, USA.
Vincent
James H
JH
D000395:Air Pollutants, Occupational / Q000032:analysis*; D005374:Filtration / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis; D016273:Occupational Exposure / Q000032:analysis*; D012680:Sensitivity and Specificity; D020711:Threshold Limit Values; D014481:United States; D017132:Workplace
D000395:Air Pollutants, Occupational