Proficiency testing standard solutions

A common way to assess the matrix bias is to analyse a drinking water (therefore containing a matrix) in the proficiency testing. For this analysis, laboratories calibrate their instruments using standard, commercial or in-house solutions. If a CRM is available, a possible matrix effect can be corrected by adjusting operational instrument parameters to match the certified value. 

For this aim, three proficiency testing (PT) campaigns were organized within the SWIFT-WFD project, mainly dedicated to the determination of the list of priority pollutants annexed to the WFD. The SWIFT-WFD PT campaigns, one per year for three years, were organized on 17 reference materials (RMs) including 5 matrix RMs at natural concentration levels, 3 at low fortified concentration levels, 4 at fortified concentration levels, and 5 multi-analyte blind standard solutions, targeting the analysis of... 

Figure 3 (A) Ordered results from a proficiency test of 12 analysts. The amount of substance concentration of carbonate in the distributed test solution was assigned as 27.8+0.2 mmol I with a target standard deviation for the group of I.OmmolP The consensus mean was 28.9mmoll with a sample standard deviation of 1.3 mmol I No points were outliers by a Grubbs test. (B) Data of (A) transformed to a z-score. Filled circles z, = ((x,- - Assigned value)/Target standard deviation), Open squares z,-= ((z -- Consensus mean)/Sample standard deviation). Lines are drawn at z= +2 and +3.

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