Preparation and certification of benzoic acid reference material for calorimetry analysis

Benzoic acid reference material is indispensable for bomb calorimeter instrument calibration and validation of gross calorific value (GCV) analysis of any substance. In this work, we demonstrated the preparation of benzoic acid reference material through a homogeneity study, round-robin analysis, and stability study. Two-factor analysis of variance (ANOVA) test for gross calorific value in the randomly selected sub-samples of benzoic acid exhibits a lower F_TS value than the F_crit value, indicating that the samples are sufficiently homogeneous. The calculated uncertainty of between-bottle (u_bb) and uncertainty of homogeneity (u_hom) for GCV of benzoic acid in the sub-samples were found as 1.82 and 4.42 ​cal/g respectively. We found that the observed homogeneity (u_{hom (Finding)}) value is lower than the assumed homogeneity (u_{hom (Assume)}) value for the prepared benzoic acid reference material. Overall observations confirm that the sub-samples are sufficiently homogeneous. Moreover, the round-robin analysis/or inter-laboratory comparison analysis was conducted to assign the gross calorific value and determine the characterization uncertainty. The seventh order of Grubbs' analysis was done using robust estimator Alogoritm A to assign the GCV of benzoic acid. Finally, the measurement uncertainty of the assigned GCV of benzoic acid was calculated with the combined uncertainties from various sources.