Representative Analysis Results Require Adequate Sample Preparation

The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question is why the product does not match the specifications although the production parameters have not been changed in any way.

The possibility that the tested product is indeed deficient cannot be excluded. However, it is often not the product itself which causes irregular analysis results but a lack of understanding of the steps which come before the analysis. Analog to an iceberg which is for the greatest part under water, only a small part of the sum of errors is perceived whereas the major part of potential errors is not taken into account. One reason for this may be that the high accuracy of modern analytical equipment is regarded as the maximum absolute error of the sample preparation process. Another reason may be the fact that sampling and sample preparation are done in a traditional way which has become a routine over the years and is no longer regarded as having a critical influence on the subsequent analyses.