A Review of the IAG GeoPT™ and Certification Programmes, their Protocols, and the Differences between the Original and Potential Modifications to the Certification Protocol

The IAG conducts two programmes, the GeoPT (TM) proficiency test and a certification programme that are closely interconnected. Both support the quality control/quality assurance activities of geochemical laboratories. Each derives an estimate of 'true value' for a number of samples, but arrives at that estimate, and its uncertainty, differently. This review discusses the history of the two programmes and compares the 'true values' and their uncertainties obtained through each. It then considers 'fitness-for-purpose' issues related to both GeoPT (TM) and certification uncertainties. Issues related to potential modification of the IAG protocol for certification are also considered.