Analyst qualification for the aliquot sampling operation under conditions close to routine analysis

Aim. This study aimed to assess the performance of analysts conducting the standard aliquot sampling operation with a pipette in an inter-laboratory trial under conditions closely resembling routine analytical practices. Materials and methods. Certified 2 mL Mohr pipettes ISO class A; a gravimetric procedure for determining the delivered volume and the corresponding equipment that meets the ISO 4787:2021 requirements; the State Pharmacopoeia of Ukraine statistical approaches. Results and discussion. The testing involved 25 analysts from 6 laboratories performing volume measurements using characterized pipettes in a "blind" experiment (the analyst was unaware of the testing, and the supervisor instructed them to work according to routine procedures). Acceptance criteria were developed based on reliable glassware verification and compliance with the requirements of normal analytical practice (NAP) regarding individual volume deviations from the certified value. The average volume deviation did not meet ISO requirements for 40 % of participants (incorrect volumetric glassware verification), individual deviations exceeded NAP requirements for 68 % of participants (incorrect routine analysis performance), and the standard deviation for replicate volume measurements exceeded the requirements for 32 % of participants (unreliable volumetric glassware verification). Conclusion. The "blind" testing revealed a significantly higher level of non-compliance compared to traditional proficiency testing (PT). This confirms our assumption that the results of traditional PT reflect the laboratory's best capabilities rather than routine testing practices and cannot be used to assess uncertainty in routine analysis. "Blind" testing provides a more realistic assessment of uncertainty in routine analysis. The high level of non-compliance calls for corrective actions across the entire pharmaceutical sector rather than in individual laboratories