Mass fraction of As, Cd, Cu, Mn, Pb, Se and Zn in bovine liverCRM 185R
Bovine Liver is one of a series of three meat reference materials. It is intended to be
used for the control of contaminants in liver. The other two reference materials are CRM 184 Bovine Muscle with lower contaminant concentrations and CRM 186 Pig Kidney with still higher levels of contaminants.
BCR-185R is intended to replace the BCR CRM 185 Bovine Liver of which, due to its success in environmental and food control, the supply is exhausted.
The bovine livers (in total 28) selected for the preparation of the CRM originate from 4 year old cows of Belgian origin which where slaughtered in June 1996 in the Stedelijk Slachthuis in Geel under the same conditions as animals for human consumption and after the same veterinary controls. The livers were brought to IRMM the day of slaughtering where they were immediately prepared for jaw crushing: the connective tissue was removed in a clean cell and pieces of 10 cm
by 5 cm by 1 cm were cut using ceramic knives and immediately frozen to -20°C. From each liver samples for Cd analysis by SSZAAS were taken. The pieces of each liver were processed separately. After jaw crushing under liquid nitrogen in a specially adapted jaw crusher, in which the parts which come into contact with the sample are made out of teflon, the precrushed product was lyophilised.
Although the cows selected were of approximately the same age the Cd content was varying between 0.17 and 1.15 mg/kg. In order to obtain a homogenous final product the livers were divided into 3 categories and mixed yielding 3 batches:
I: Cd content < 0.4 mg/kg
II: Cd content between 0.4 and 0.7 mg/kg
III: Cd content >0.7 mg/kg
On the basis of the weight and Cd content of each liver the mean Cd content was calculated for each batch. Portions of batch I and III were mixed in such a ratio to yield in the mixture a Cd content close to that of batch II and processed through ball-milling. Also batch II was ball-milled. The resulting 2 ball-milled portions were mixed, sieved at lower 0.125mm and homogeneised in the turbula mixer. By applying this mixing technique it was possible to prepare an extremely homogenous material. This was proven by the later microhomogeneity study. The resulting material was filled into brown glass vials, each vial containing 15 g powder. All vials were put into the freeze dryer, dried to the final moisture content, filled with argon and simultanously closed with teflon protected rubber stoppers and sealed with aluminium caps. 2400 vials were produced, each containing 15 g of powder. The moisture content in the final product was determined by Karl Fischer titration on 10 vials taken throughout the batch and amounted to (1.32 +/- 0.15) %. The production was finished in September 1996.
keywords: Biological material, Animal tissue, Trace elements, Heavy metals, Foodstuff