This study compares the results of three certified methods, namely differential scanning calorimetry (DSC), the mass balance (MB) method and coulometric titrimetry (CT), in the purity assessment of ferulic acid certified reference material (CRM). Purity and expanded uncertainty as determined by the three methods were respectively 99.81%, 0.16%; 99.79%, 0.16%; and 99.81%, 0.26% with, in all cases, a coverage factor (k) of 2 (P=95%). The purity results are consistent indicating that the combination of DSC, the MB method and CT provides a confident assessment of the purity of suitable CRMs like ferulic acid.
Keywords: ASTM, American Society for Testing and Materials; CRM, certified reference material; CT, coulometric titrimetry; Certified reference material; Coulometric titrimetry; DAD, diode-array detector; DSC, differential scanning calorimetry; Differential scanning calorimetry; EDQM, European Directorate for Quality Medicine; Ferulic acid; GUM, Guide to the Expression of Uncertainty in Measurement; ISO, International Organization for Standardization; MB, mass balance; Mass balance; RM, reference material; SI, International System of Units; Uncertainty; WHO, World Health Organization.