In the framework of a good laboratory praxis the emphasis is placed to the quality of reproducible results. For this reason are very useful methods of mathematical statistics, which, in the form of regulating diagrams, can help to the speed identification of that reults, which are outside the requisite tolerances. There are a lot of various samples used for statistical regulation. One possibility how to controll the efficiency of whole analytic process, from prepearing to the final determination, is using of surrogate standard.

For PCB determination in various types of water were found as a surrogate standrads following two compounds: 2,4,5, 6-tetrachlor-m-xylen and decachlorbifenyl. Above mentioned compounds were examined during relativly complicated determination of PCB in beer. The concentration was determined by Shewhart,s diagrams for individual values and sliding span according to standard ČSN ISO 8258. This example of PCB determination in beer indicates the possibility to use surrogate standards as a powerful instrument for determination of results quality.