The homogeneity of the stock with respect to its antimony, copper, gold, selenium, silver and zinc was investigated using twenty-two bottles chosen according to a stratified random sampling scheme. Two splits were analysed from each bottle. Instrumental neutron activation was used on 0.5g sample for antimony, selenium, silver and, zinc, and on a 5g sample for gold. No evidence of inhomogeneity was observed for all six elements. Use of a smaller sub-sample will invalidate the use of the certified value and associated parameters.
Further details are available in the certification report.
Various elements were analyzed by methods of each laboratory's choice. Fifteen elements were given recommended values and a further seven elements had provisional values assigned. These certified values are valid until 2005. The stability of the material will be monitored every two years. Purchasers will be notified of any significant changes.