Ryoko Iwasawa

Certified calibration solution reference material for the determination of perfluorooctane sulfonate from the National Metrology Institute of Japan (NMIJ)

A new calibration solution reference material for the determination of perfluorooctane sulfonate anion (PFOS) and its salts has been issued as a certified reference material (CRM) by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The purity amount-of-substance fraction of raw material potassium perfluorooctane sulfonate (K-PFOS) was evaluated based on the results obtained using the freezing point depression method, and the purity mass fraction of the raw material was calculated using the average molar mass of impurities, the molar mass of K-PFOS, and the purity amount-of-substance fraction. The certified concentration of this CRM was obtained by multiplying the dilution ratio of the raw material in a prepared solution (methanol) determined from the gravimetric blending method by the purity of the raw material. The preparation concentration of K-PFOS as a certified value of NMIJ CRM 4220-a was determined to be 9.93 mg kg−1. In addition, the standard uncertainty of the certified value was evaluated from the purity evaluation as well as from sample inhomogeneity, instability, and preparation variation obtained from LC/MS measurements of different gravimetrically prepared solutions of the NMIJ CRM. Consequently, the expanded uncertainty was estimated to be 0.15 mg kg−1 with a coverage factor k = 2 corresponding to the half-width of estimated confidence interval of approximately 95%.

Certified reference material for the determination of perfluorooctane sulfonate in acrylonitrile-butadiene-styrene resin (NMIJ CRM 8155-a)

ABSTRACT A certified reference material (CRM) for the determination of perfluorooctane sulfonate (PFOS) in acrylonitrile-butadiene-styrene (ABS) resin (NMIJ CRM 8155-a) has been issued by the National Metrology Institute of Japan (NMIJ). The bulk material was prepared by mixing commercial ABS resin powder and potassium PFOS and cut into square plates (20 × 20 mm, 2 mm thick) as the CRM. Analytical processes combined with isotope-dilution mass spectrometry and liquid chromatography/mass spectrometry were optimised and applied for characterisation. One of the approaches adopted by NMIJ for certification is that results from two or more primary methods of measurement should be used; thus, two optimised isotope-dilution mass spectrometric methods (Methods 1 and 2 with reprecipitation and with reprecipitation/solid phase extraction, respectively, were validated mutually and employed) were used to determine the certified value. Homogeneity and stability of the square plates were evaluated and their uncertainty contributions (as relative standard uncertainties) were 1.43% for inhomogeneity and 6.96% for approximately two years’ instability. The certified mass fraction of linear PFOS (heptadecafluoro-1-octanesulfonic acid) in the CRM with expanded uncertainty (coverage factor k = 2, approximately 95% confidence interval) was (33.1 ± 5.0) mg kg−1 as free acid of PFOS.

Certification of reference materials for the determination of alkylphenols

Certified reference materials (CRMs) are playing an increasingly important role in national and international standardizing activities. In Japan, primary standard solutions for analyses of endocrine disrupters are supplied under the national standards dissemination system named the Japan Calibration Service System (JCSS). For the traceability on reference materials used for preparation of the primary standard solutions based on the JCSS, the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) has developed and certified high-purity reference materials of alkylphenols as NMIJ CRMs, such as 4-n-nonylphenol, 4-tert-octylphenol, 4-n-heptylphenol, 4-tert-butylphenol, and 2,4-dichlorophenol. Thereafter, it is essential to determine the alkylphenols by using these solutions based on the JCSS for environmental monitoring and risk assessments because analytical values obtained by using the solutions can ensure the reliability and traceability of the chemical analyses.