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Trichloroacetic acid is known as one of the harmful disinfection byproducts with chlorine of tap water and is regulated according to legally binding standards in Japanese Drinking Water Quality Standards. We developed a high-purity trichloroacetic acid reference material, NMIJ CRM 4074-a, with certified purity as a traceability source of standard solution supplied under the Japan Calibration Service System (JCSS). As trichloroacetic acid is hygroscopic, water could be the main impurity. Although all impurities in the sample can be possibly detected by the freezing point depression method (FPD), it was unclear for trichloroacetic acid whether water was detected by FPD owing to evaporation of water from the sample during fusion. Therefore, we confirmed that water in trichloroacetic acid was detected as an impurity by FPD. The procedure was validated from an increment of purity by FPD due to reduction of water content and an agreement of purity by FPD with those by neutralization titrimetry (NT) and mass balance approach (MBA), both methods were based on different measurement principles from FPD. The certified value was determined to be (0.999 ± 0.003) kg kg−1 from the purity assay by FPD and NT, and uncertainties due to the homogeneity and stability of the CRM were included in the expanded uncertainty. The reliability of the certified value was verified by the agreement of purities by FPD, NT, and MBA. [ABSTRACT FROM AUTHOR]

The assessment of primary calibrator purity is critical for establishing traceability to the International System of Units (SI). Recently, quantitative nuclear magnetic resonance (qNMR) has been used as a purity determination method for reference material development, and many related measurement techniques have been designed to acquire accurate and reliable results. This review introduces the recent advances in these techniques (including multidimensional methods), focusing on the application of qNMR to reference material preparation. [ABSTRACT FROM AUTHOR]

A mass balance method enables accurate determination of the purity of monosaccharides by incorporating the results obtained by various analytical techniques. High‐performance anion exchange chromatography with pulsed amperometric detection was used to quantify nonchromophoric impurities structurally related to the analyte. Organic acids as candidates of monosaccharide impurities were analyzed by ion chromatography with conductivity detection. Liquid chromatography with photodiode‐array UV detection was performed to detect other organic impurities. Karl‐Fischer coulometry with oven‐drying method was used to measure the water content in the samples. Finally, nonvolatile inorganic impurities were determined by thermal gravimetric analyses. The purities of the monosaccharides, glucose, galactose, fructose, and mannose, in kg/kg were (0.9983 ± 0.0004), (0.9962 ± 0.0005), (0.9999 ± 0.0004), and (0.9991 ± 0.0005), respectively. The mass balance method provides system of units (SI)‐traceable purity values, which can be applied to primary reference materials for assigning a certified value for the target monosaccharide in certified reference materials. [ABSTRACT FROM AUTHOR]