Sammenlignende laboratorieprøving (SLP) – Industriavløpsvann SLP 1756

Exercise number 56, named 1756, was organised in March - June 2017 with 73 participants, of whom 71 reported results. The "true" values were distributed to all participants on June 16th 2017, to allow laboratories with deviating values the opportunity to start their troubleshooting as soon as possible. Many of the analyses were conducted following the Norwegian Standard (NS) or other documented methods (table B1). For the determination of total phosphorus and total nitrogen, some laboratories employed simplified methods. Employing more sophisticated methods would probably increase the quality of the analyses. 82 % of the results in exercise 1756 were acceptable, which is comparable to results from the previous exercises (table 1). The practice of continuous quality assurance [Hovind 2006 et. al] is a prerequisite to be able to evaluate methods and routines. Standard reference materials (SRMs) are recommended for controlling the results and methods, but in lack of SRMs, samples from previous exercises may be used.