ScienceAsia 28 (2002) : 351-358 |doi: 10.2306/scienceasia1513-1874.2002.28.351

Production and Certification of
In-house Rice Flour Reference Material

Wipharat Chuachuad^a, Juwadee Shiowatana^b,*, Niorn Chukanchanapituk^b, Waret Veerasai^b, Scott Willie^c and James Walker McLaren^c,

ABSTRACT: An in-house reference material for trace metals in rice flour was produced. Certification of concentrations of fifteen elements based on at least two independent methods was carried out. The analytical techniques included ICP-AES, ICP-MS, ETAAS, FAAS and voltammetry. Out of the 15 elements, 13 elements, namely Na, K, Mg, Ca, Ba, Cu, Zn, Fe Mn, Co, Ni, Pb and Cd, could be certified whereas only reference values were given to Cr and V because the concentrations of these two elements were so low that only one analysis method could successfully detect them. Statistical tests for the study of homogeneity at 95 % confidence level did not reveal significant differences between the within-bottle and between-bottle variation. The rice flour material is considered to be homogeneous at 250-650 mg sample sizes. No significant change was observed in a long-term stability study of the material over a period of 5 months and a short-term stability study at an elevated temperature of 50^oC for a period of 5 weeks. A comparison of results obtained from independent methods was made before certified values were calculated using both means and weighted means. The reference materials have been distributed for use in laboratory quality assurance.

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a Department of Chemistry, Faculty of Science, Naresuan University, Phitsanuloke 65000, Thailand.
b Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
c Chemical Metrology, Institute for National and Measurement Standard, National Research Council of Canada, Ottawa, Ontario K1A OR6, Canada.

*Corresponding author, E-mail: scysw@mahidol.ac.th

Received 21 Mar 2002, Accepted 19 Apr 2002