Volume 2, Issue 5 (May 2005)
The Performance of Different Analytical Approaches Measuring Respirable Quartz In the Workplace Analysis Scheme for Proficiency (WASP) and the Precision and Limit of Detection of the Direct On-Air-Filter Analysis Methods
This paper describes the technique used to prepare replicate samples of respirable α-quartz on GLA5000 filters and the precision of the samples, and it compares the performance of different analytical methods for the measurement of quartz in air, used by laboratories that participate in the United Kingdom (UK) proficiency-testing program the Workplace Analysis Scheme for Proficiency (WASP). The average within laboratory relative standard deviation (RSD) of results submitted by a laboratory using an on-filter analysis method was 8.8%. The small number of laboratories using indirect methods in the program produced the most variable data (6–34 % RSD). A robust estimate of analytical precision for an 8-h sample containing 0.05 mg/m3 of quartz (53 μg on the filter) is about ± 12 % (1σ) for the direct on-filter XRD method and about ± 14 % (1σ) for the direct on-filter infrared method. The analytical precision estimates for a 4-h sample (26 μg on the filter) are likely to exceed 30 % (1.96σ). The limits of detection for the direct on-filter analysis methods are comparable with those stated in the NIOSH methods [1,2], and a comparison of the performance of X-ray diffraction and infrared analysis shows that the difference between results produced from the two techniques is insignificant for some types of dust(s).