An update on analytical methods, quality assurance and quality control used in the Greenland AMAP programme: 1999-2002.

The majority of analytical results in the Greenland AMAP (Arctic Monitoring and Assessment Programme) are produced by laboratories that participate regularly in performance studies. This makes it possible to judge the quality of the results based on the objective measurements made by independent assessors. AMAP laboratories participated, while analysing the AMAP samples, in the QUASIMEME laboratory performance study programme, and in two other smaller laboratory performance study programmes. Here is a system presented where the laboratory performance studies are used to calculate a constant error and a proportional error for each analyte. The calculations are performed by the trial and error method that sets the proportional and the constant error so that the 95%, the 68.2%, and the 50% confidence limits fit as well as possible with the data. The constant error is roughly the same as the detection limit defined as the highest concentration where zero is inside the 95% confidence interval. The relative errors of the trace analyses, i.e. the relative deviation of the result obtained by the AMAP laboratory from the assigned value, are in most of the cases less than 25% which is regarded as acceptable by the QUASIMEME. Usually the errors, especially for trace elements, are less than 12.5%, while errors for trace organics below 1 microg kg(-1) may rise to 50% or more.