A certified urea reference material (NMIJ CRM 6006-a) as a reliable calibrant for the elemental analyses of amino acids and food samples.
We examined the reliability of a certified reference material (CRM) for urea (NMIJ CRM 6006-a) as a calibrant for N, C, and H in elemental analyzers. Only the N content for this CRM is provided as an indicative value. To estimate the C and H contents of the urea CRM, we took into account the purity of the urea and the presence of other identified impurities. When we examined the use of various masses of the calibrant (0.2 to 2 mg), we unexpectedly observed low signal intensities for small masses of H and N, but these plateaued at about 2 mg. We therefore analyzed four amino acid CRMs and four food CRMs on a 2-mg scale with the urea CRM as the calibrant. For the amino acid CRMs, the differences in the analytical and theoretical contents (≤0.0026 kg/kg) were acceptable with good repeatability (≤0.0013 kg/kg in standard deviation; n = 4). For food CRMs, comparable repeatabilities to those obtained with amino acid CRMs (≤0.0025 kg/kg in standard deviation; n = 4) were obtained. The urea CRM can therefore be used as a reliable calibrant for C, H, and N in an elemental analyzer.
National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST).
Nobuyasu
N
Itoh
Taichi
T
Yamazaki
Ayako
A
Sato
Masahiko
M
Numata
Akiko
A
Takatsu
D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D002138:Calibration; D002244:Carbon / Q000032:analysis; D005396:Fish Products / Q000032:analysis; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D006859:Hydrogen / Q000032:analysis; D008892:Milk / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis; D012015:Reference Standards; D015203:Reproducibility of Results; D013025:Glycine max / Q000737:chemistry; D014508:Urea / Q000032:analysis*
D000596:Amino Acids; D002244:Carbon; D006859:Hydrogen; D014508:Urea; D009584:Nitrogen