Wageningen Evaluating Programmes For Analytical Laboratories (Wepal): A World Of Experience

A regular and independent assessment of the analytical performance of a (environmental or agricultural) laboratory is recommended as an important means of assuring the validity of analytical measurements. A common approach to this assessment is the participation in an independent proficiency testing scheme (PT). Participation in such a scheme is just one aspect of the overall quality strategy of the laboratory. Participation in a proficiency testing scheme is a system for objectively evaluating the performance of the laboratory by comparing laboratory's results with those of other laboratories at regular time intervals (preferably a minimum of four times a year). The Wageningen University in The Netherlands organizes several of these world-wide laboratory evaluating programs on chemical analysis of soils, plants, manure/refuses and sediments under the "umbrella" organization called WEPAL: Wageningen Evaluating Programmes for Analytical Laboratories. WEPAL is accredited for the organization of Interlaboratory Studies by the Dutch Accreditation Board since April 16, 2000. In this contribution, a short overview of the running PT-schemes is given. Attention is paid to the extra advantages of participation in an extensive international proficiency testing program, e.g., availability of reference materials and exchange of experiences.