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Our principles

Analytical results predominantly take the responsibility for the decision about the quality of the analysed products. Therefore, the scientific competence of analytical laboratories is core to reliable analytical results. The overall objective of PROOF is the improvement of the reliability of laboratories' analytical results. The Competence Schemes provided by PROOF thus follow the objective of being up-to-date and tailor-made to be close to current and future analytical needs. Moreover, the complex analytical challenges as well as the laboratories' clients' perspectives are taken into account when designing and evaluating the PROOF Competence Schemes. The evaluation of the PROOF Competence Schemes therefore considers different perspectives like for example the comparability (z-score model) and trueness (recovery of spiked levels) of the reported analytical results of participating laboratories.

Rapid implementation

PROOF organises Competence Schemes for those analytical parameters that are not available off-the-shelf. Unexpected and/or anticipated upcoming analytical question require a fast adjustment of the laboratories' analytical skills. Sometimes no standardised methods are available for new analytes and thus the laboratories' need for proving the robustness and validity established in-house methods by means of Competence Schemes is of high importance. This also applies for suitable Reference Material. By organising Competence Schemes for specific analyte/matrix combinations, PROOF is able to provide to laboratories surplus Reference Materials.


The design of each of our Competence Schemes starts with the careful and scientifically based selection of analytes and matrices in question. PROOF pays particular attention to analytically reasonable analytes, always in the context of the matrix in question. Following this approach, PROOF develops well-founded and customised designs, taking into consideration the complex analytical challenges as well as the laboratories' clients' perspectives. We want to support laboratories to improve the quality of their results in particular related to challenging analytical questions.

High quality

The high quality of the Test Material is an important prerequisite for a meaningful Competence Scheme: High quality in terms of stability, validity and representativeness.
More than 16 years of experiences in the field of Test Material Preparation and the evaluation of Competence Schemes are basis to this high quality. PROOF will prove this by providing homogeneity and stability data of the corresponding Competence Scheme. 


PROOF-ACS GmbH is an independent company, solely financed by organisation of Competence Schemes and the distribution of Reference Material. Just three persons (Dr. Silke Bruns, Dr. Birgit Schindler and Dr. G√ľnter Lach) hold 100% of the companies' shares. Other parties are not involved at all. Therefore, PROOF is able to assess analytical results independent and unaffected of any external influences.


PROOF sticks to comprehensive transparency. As a consequence, customers receive thorough insight in the design, homogeneity and stability tests, the applied statistics and the way of data assessment.