Accurate determination of the noble metals II. Determination methods

As was shown in the first part of this contribution, accurate analytical determination of the noble metals in rocks, ores and alloys needs a sophisticated sample pretreatment prior to the final determination step of the preconcentrated elements. For this many instrumental and classical methods are available, the choice of which is usually dictated by levels of precious metal to be handled, nature of sample matrix and availability of the instruments. For trace levels (μg/g range) flame atomic absorption and inductively coupled plasma (ICP) emission spectrometry can be used. ICP emission is favoured because of ease of multi-element operation. At the sub-μg/g level furnace atomic absorption and nuclear techniques (mainly neutron activation) are favoured. Minor and % concentrations are best handled by X-ray fluorescence. The use of standard reference samples and internal and external laboratory control schemes are essential to the accurate determination of precious metals.