CERTIFIED CALIBRATION SOLUTION REFERENCE MATERIAL FOR THE DETERMINATION OF BENZO[A]PYRENE FROM THE NATIONAL METROLOGY INSTITUTE OF JAPAN (NMIJ)

A new calibration solution reference material (NMIJ CRM 4213-a) for benzo[a]pyrene (BaP) analysis was prepared and certified by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Certification of CRM 4213-a was carried out at NMIJ using a freezing point depression method and gravimetric preparation. Certified concentration of this CRM was obtained by multiplying the dilution ratio of raw material BaP in a prepared solution with purity of the raw material. Purity of our raw material was calibrated by a gas chromatograph with flame ionization detection using that of high-purity BaP purified by using a high performance liquid chromatograph with a normal phase column, because purity determination of the raw material by a differential scanning calorimeter (DSC) couldn't be assessed directly. The purity of high-purity BaP was assessed in the molar fraction by DSC, and then the purity of the mass fraction was calculated based on average molecular weight of impurities and the purity of the molar fraction. CRM 4213-a has been developed with a certified value of 99.2 mg/kg. Uncertainty was evaluated from purity assessment as well as homogeneity and stability of the CRM, and expanded uncertainty was estimated as 3.9 mg/kg with coverage factor k = 2, corresponding to an estimated confidence interval of approximately 95%.