ISO 17025 Quality Manual Template
Thursday, June 05, 2008
Sampling - 5.7
Sampling is integral to the measurement process and should be an important consideration in meeting the needs of the end user of the results. Sampling quality has not traditionally been thought to be part of measurement quality, but it is a key aspect. In fact, sampling frequently is a major contributor to measurement uncertainty. If sampling is not considered, the values of uncertainty estimates will often seriously underestimate the real uncertainty of the system.
Laboratories often do not sample materials outside of the lab. However, labs are still responsible for subsampling and homogenizing the sample to ensure that a representative test portion is used for analysis. If the samples are not collected correctly and subsampled properly, data obtained will not be indicative of the true concentration no matter how well the lab performs.
Labs sometimes assume that the samples they receive are homogenous and do not require a specific method to subsample the material to be tested. However, this assumption can result in problems. The lab shall have documented procedures for subsampling and/or homogenization to ensure that a representative test portion is used for analysis. Appropriate considerations should be made for multiphase and lable samples, aseptic handling, cross-contamination, and other issues to reduce the known errors associated with sample heterogeneity. Validation procedures should include all the steps normally undertaken within the lab., including any subsampling of test samples.
Laboratories often do not sample materials outside of the lab. However, labs are still responsible for subsampling and homogenizing the sample to ensure that a representative test portion is used for analysis. If the samples are not collected correctly and subsampled properly, data obtained will not be indicative of the true concentration no matter how well the lab performs.
Labs sometimes assume that the samples they receive are homogenous and do not require a specific method to subsample the material to be tested. However, this assumption can result in problems. The lab shall have documented procedures for subsampling and/or homogenization to ensure that a representative test portion is used for analysis. Appropriate considerations should be made for multiphase and lable samples, aseptic handling, cross-contamination, and other issues to reduce the known errors associated with sample heterogeneity. Validation procedures should include all the steps normally undertaken within the lab., including any subsampling of test samples.
Labels: measurement uncertainty, sampling, test
