The Uncertainty on using Graduated Volumetric Glassware for the Concentration of Samples (Concentration Tube) and its Effect on Measurement Accuracy

Although each step in the quantitative analysis of trace substances is susceptible to marked variability, it is assumed that there is only a negligible difference in the quality of concentration tubes, and that the concentration step, which is performed in such tubes under a nitrogen gas stream to obtain the desired volume, generates very few sources of variation. Therefore, using a quantitative method for measuring benzo(a)pyrene (B(a)P) as a test procedure, we estimated uncertainties involved in each step, from sampling to instrumental analysis, and evaluated the effect of concentration tubes on the measurement accuracy based on an uncertainty analysis. As the results, the combined relative standard uncertainty for the determination of 1.0 mg/L of (B(a)P) was 3.3-5.4%, of which the contribution of concentration tubes was 67.3-87.8%. The present study demonstrated that uncertainty on use of concentration tubes affects measurement accuracy, and highlighted the need to introduce precision control in vessel use.