title: Inter-laboratory analysis of endotoxin in cotton dust samples.
abstract: BACKGROUND
  Currently there are no mandated exposure limits for endotoxin, but recommended limits have been proposed and interest expressed in developing quantitative standards for endotoxin. A limitation for developing a quantitative standard for endotoxin is the measurement variability between laboratories. Inter-laboratory variability of up to four orders of magnitude has been reported for replicate samples. To evaluate both the intra- and inter-laboratory variability, Round-Robin studies were conducted using replicate samples of cotton dust.
  
  
  METHODS
  Replicate samples of cotton dust were collected using vertical elutriators (VE) in a model cardroom. Each participating laboratory evaluated the samples for endotoxin using: their normal extraction procedure; a common extraction procedure; and a common extraction procedure and the same type and lot of a commercially available endotoxin kit.
  
  
  RESULTS
  These studies demonstrated that both intra- and inter-laboratory variability is reduced by using a common extraction protocol and a common assay kit; however, significant differences remained between the laboratories.
  
  
  CONCLUSIONS
  The data suggest that intra-laboratory assays can be used to assess the relative differences between endotoxin samples, however, the inter-laboratory variability suggests that limitations remain for developing a reliable exposure assessment assay that could be used for a quantitative exposure standard.
authors.affiliation: Graduate Program in Public Health, Eastern Virginia Medical School, Norfolk, Virginia 23501-1980, USA. jacobsrr@evmsmail.evms.edu
authors.forename: Robert R
authors.initials: RR
authors.lastname: Jacobs
authors.forename: David
authors.initials: D
authors.lastname: Chun
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis*; D032561:Cotton Fiber; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000032:analysis*; D019981:Health Care Sector; D007221:Industry
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D004731:Endotoxins