Water Framework Directive, watch list method : analysis of diclofenac in water : validation report, according to ISO 17025 requirements

Validation of an analytical method is a necessary step in controlling the quality of quantitative analysis. Method validation is an established process which provides documentary evidence that a system fulfils its pre-defined specification, or shows that an analytical method is acceptable for its intended purpose. The purpose of the present study was to validate an SPE-LC-MS/MS method for the determination of diclofenac in surface water samples according to the requirements laid down in ISO 17025. The calibration curves, working ranges, recoveries, detection and quantification limits, trueness as well as repeatability were determined. The uncertainty budget was estimated following a top-down approach based on in-house validation data. The expanded relative uncertainty was estimated as 13 and 8% at low and high concentration levels respectively, based on 15 replicate measurements on 5 days, and as 30 and 18% for a single measurement performed on a single day.