The certified values are valid until April 30, 2035.The stability of the material will be monitored every two years for the duration of the inventory.Each bottle was purged with nitrogen and sealed in a laminated polyethylene - foil pouch to prevent oxidation. The homogeneity of the stock was investigated using fifteen bottles chosen according to a stratified random sampling scheme. Subsamples of 0.25 grams were digested using hydrochloric, nitric, hydrofluoric and perchloric acids, and analyzed by inductively coupled plasma – optical emission spectrometry for arsenic, cobalt, copper and nickel.Samples of 0.15 grams were analyzed for sulphur using a combustion apparatus with infrared detection.The concentration of sulphur was determined using combustion followed by infrared spectrometry, gravimetric analysis, various acid digestions and fusions followed by inductively coupled plasma – optical emission spectroscopy and X-ray fluorescence.The concentration of sulphur species was determined using the same methods as sulphur, plus leaches followed by inductively coupled plasma – optical emission spectroscopy or high pressure liquid chromatography.Informational values for thirty-eight analytes, shown in Table 3, were derived from the means of a minimum of 3 sets of data.
The product was blended, and then bottled in 100-gram units.
Three subsamples were selected from each of the combined bottles i.e. Gold was determined in subsamples of 30 grams using fire assay pre-concentration followed by determination using inductively coupled plasma – mass spectrometry.
Use of a smaller subsample than specified above will invalidate the use of the certified values and associated parameters.
Additionally, a set of 15 pairs of bottles was chosen according to a stratified random sampling scheme.
Each pair of consecutively numbered bottles was combined to form a 200 gram sample.