The certified reference material CRM-278R is intended to replace, BCR CRM 278 (trace elements in mussel tissue) which, due to its success in environmental
control, is presently exhausted. Care was taken to find a material with a composition similar to that of the original mussel tissue.
The material selected originates from a batch of mussels (mytilus edulis) collected in the Dutch Waddensea in 1986 together with the original CRM 278. The initial preparation of the material under the responsibility of the Environment Institute was done separately from the preparation of CRM 278, but using the same procedure: after collection, the mussels were cooked under pressure at 120 °C for 30 s and the shells were removed. The mussels were then instantly deep frozen (liquid nitrogen) and stored at a temperature below - 28 °C. Subsequently, the material was freeze-dried during 20 h and ground in a stainless steel mill which may have caused some contamination with Fe. Upon freeze-drying the material lost 73.5 % of its mass. It was then further processed in the laboratories of the Environment Institute by grinding in a zirconia ball mill and sieving through a 125 ìm sieve. Finally the dried powder was mixed for two weeks under dry air (which was replaced at least twice a day) in a special polythene lined mixing drum. In 1996 the material was transferred to the Institute for Reference Materials and Measurements, where after a 2 h turbula mixing the material was again freeze-dried for 30 h to reduce its moisture content to ca. 1 % and homogenised during 2 h in the turbula mixer. Sampling was done under controlled dry air (< 100 ppm H2O) using an accurate feeder with teflon lining. The material was sampled in 8 g units in vials. The vials were filled with argon and closed with teflon protected rubber stoppers and sealed with aluminium caps. The moisture content in the final product was determined by Karl Fischer titration on 20 vials taken during production and amounted to (1.3 ± 0.2) %. In total 1978 vials were produced. keywords: Biological material, Animal tissue, Trace elements, Heavy metals, Foodstuff |
