Second Collection of Card-Generated, Vertically Elutriated Dust for Comparison Endotoxin Assays

Previously, an elaborate cotton blending and dust collection protocol was developed and implemented to produce uniform, vertically elutriated dust samples that were used in a two-part interlaboratory endotoxin assay study. The results from that study generated interest in extending the interlaboratory endotoxin assay study. To satisfy this need, a second series of dust samples on glass filters, as well as on the polyvinyl chloride filters used previously, were collected. Three sources of cotton were used. The cottons were blended to produce a uniform and homogenized cotton, and then carded. The dust collection was made on vertical elutriators using the model cardroom at the Cotton Quality Research Station in Clemson, SC. Dust samples containing a low, medium and high endotoxin concentration were obtained. A full 120 separate collection runs were made and they resulted in more than 1500 dust samples on polyvinyl chloride filters and 1500 dust samples on glass filters, each with 0.3 to 0.8 mg cotton dust per filter. The dust samples collected should satisfy the need for dust samples for present and future endotoxin assay studies. At the 1998 Beltwide Cotton Conferences, the results of the first phase of an endotoxin assay round-robin study were presented (Chun et al., 1998). This was followed by a report on the preliminary results of the second phase of the same study at a workshop sponsored by the American Conference of Governmental Industrial Hygienists held at Chapel Hill, NC (Chun et al., 1999a). A summary of the highlights of the first phase and the complete results of the second phase were presented at the 1999 Beltwide Cotton Conferences (Chun et al., 1999b). In the first part of the study, filter membranes with the same approximate amount and type of cotton dust were sent for analysis to laboratories that routinely perform endotoxin analyses. Each of these laboratories performed the analysis using the methodology common to their laboratory. The results showed that intralaboratory variations were small; but large and significant interlaboratory variations were observed. In the second part of the study, filter membranes with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The partial results from the second part of the study again showed that intralaboratory variations were David T.W. Chun, USDA/ARS Cotton Quality Research Station, P.O. Box 792, Clemson, SC 29633; Robert E. Harrison, USDA/ARS Cotton Quality Research Station, P.O. Box 792, Clemson, SC 29633; Victor Chew, USDAREE/ARS-SAA-OD, 1700 S.W. 23Rd Dr, Gainesville, FL 32608. Received 28 June 1999. *Corresponding author ([email protected]). 178 CHUN ET AL.: DUST FOR COMPARISON ENDOTOXIN ASSAYS small and significant variation existed between laboratories. However, when a common extraction protocol was used, the differences in results between the laboratories were reduced considerably, which suggested strongly that further standardization might reduce the differences even more, possibly to the point that interlaboratory results might become directly comparable. These findings came about partially because uniform vertically elutriated cotton dust samples were made available for study (Perkins et al., 1996). Sufficient number of dust samples were originally collected only for the tests described. However, since the above results have become public, the need for additional tests developed, and additional dust samples were collected at the USDA, Cotton Quality Research Station in Clemson, SC. It is the purpose of this report to describe the methodology used to generate additional cotton dust samples and to describe the samples generated.