The aim of the quality control of the results is to monitor the reliability and correctness of the performed tests, therefore it is a planned and reviewed process. External quality control of the results must be implemented in accordance with the requirements of PCA documents: DA-05 and DAB-07 through participation in proficiency tests and inter-laboratory comparisons. Participation in proficiency tests - on the one hand, is a tool to demonstrate competence, on the other hand, helps to maintain the quality of testing and calibration. Within the framework of internal quality control, the laboratory may, among others, use the following means, methods and techniques:
- reference materials and certified reference materials (allow verification of method correctness, equipment performance, reagent quality and analyst competence)
- addition of a template (eliminates the influence of the matrix)
- checking the calibration curve
- duplicate sample analysis
- reagent blank (to verify quality and purity of glassware and reagents)
- field blank (to verify the effect of transport and environment on the field sample)
- taking one sample twice
- determination of one parameter by two different techniques (allows verification of the correctness of the methodology used)
- Statistical techniques for developing and analysing results and tracking changes (validation of test methods; estimation of measurement uncertainties for each test method; recording, processing and archiving of measurement results using a specialised computer program or own calculation algorithms, e.g. in Excel sheets; application of significance tests, e.g. F-Sneadecor or Student's t-test)
2) PCA document DA-05 "Policy on participation in proficiency testing", 5th edition of 17.11.11 r.
3. document PCA DAB-07 "Accreditation of testing laboratories. Specific requirements", 9th edition 10.09.12 r.
4) ElkomLab document "Technical procedure T6", 2nd edition of 15.04.2013.