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Brown rice powder certified reference material, NMIJ CRM 7504-a, for the analysis of pesticide residues was developed by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Brown rice sample was harvested to contain the pesticides such as etofenprox and fenitrothion, and that was collected from a field in Ibaraki Prefecture in Japan. The certification was carried out using multiple analytical methods such as pressurized liquid extraction, homogenization, and solid-liquid extraction (shaking); the values of target pesticides were obtained by isotope dilution mass spectrometry. Certified values were 0.19 +/- 0.05 mg/kg and 0.109 +/- 0.017 mg/kg for etofenprox and fenitrothion, respectively.

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We have applied a combination of H quantitative NMR spectroscopy (H-qNMR) and chromatography (GC or LC) to establish reliable analytical methods (qNMR/GC and qNMR/LC) for organic compounds. In this method, a reference standard is used as an internal standard for both H-qNMR and chromatography to estimate relative molar sensitivity (RMS) for analytes. The RMS values are calculated from the molar ratios between analytes and the reference standard obtained byH-qNMR; and the response ratio between them obtained by chromatography. Concentrations of analytes in the organic solution can be simultaneously determined from the RMS and amount of the reference standard added in the sample solution. This analytical method is an innovative one because only one reference standard with International System of Units (SI)-traceable property value, purity, or concentration, is necessary to determine accurate concentrations of multiple organic components in organic solutions, without the respective certified reference standards for various analytes. To verify this method, a certified reference material, NIST SRM 1647f, was used. Among the 16 polycyclic aromatic hydrocarbons (PAHs) included in NIST SRM 1647f, naphthalene and benzo[a]pyrene were selected as analytes for this method, using 1,4-bis(trimethylsilyl)benzene-d as the reference standard. Each quantitative value obtained by qNMR/GC and qNMR/LC agreed with each certified value within its expanded uncertainty.

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