Quality assurance of volumetric glassware for the determination of vitamins in food

Volumetric measurements are currently used in the analytical process to determine the vitamins content in foods. The variations in stability and integrity of volumetric apparatus, although relatively small when compared with other sources of error, should be monitored. The main purpose of this study was to investigate and identify a number of variables which, in daily use, can affect the life cycle of volumetric glassware. The role of in-house metrological hierarchy, the operator’s performance and the effect of temperature was evaluated for single volume flasks, single- and multi-mark pipettes. Biased nominal capacity was applied in the calculation of water-soluble vitamins (B1, B2, B6, niacin) and fat-soluble vitamins (A, D, E) content. Persistent bias due to volumetric glassware, can reach 11%, in the results obtained for different vitamins content. The largest bias was observed for vitamin B1, perhaps due to the high amount of volumetric glassware used in the analytical procedure. This is an indication that the cost–benefit of a calibration plan should be evaluated in a rational way. The regular checking of volumetric glassware for stability and integrity is discussed on the light of the latest revision of ISO 17025.