Requirements of Reference Materials

The resulting calibration function is traceable to two reference materials for which the acid-soluble parts of nickel are certified the river clay sediment (LGC 6139, Laboratory of the Government Chemist, Teddington, UK) with a certified concentration of 38 1 mg/kg, and the soil BRM 04 (Bundesanstalt fur Materialforschung und -priifung, Berlin, Germany) with a certified concentration of 22.7 3.7 mg/kg (mean of three labs). Both materials comply with the requirements of reference materials, as mentioned above. 

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