At first glance, it may appear that a client faces a bewildering array of laboratory analytical procedures and packages and it is not immediately clear which procedure is most appropriate. These issues are discussed at greater length in the following sections. In making analytical selections, clients should carefully consider the detection limits of the various procedures. Every measurement over the entire analytical range has some degree of uncertainty associated with it. Our procedures have been developed in order to offer the best quality precision at all concentration ranges.
All methods have limitations to some degree.
The same detection limits can not be provided for sample matrices such as soils and silts because of interferences caused by the larger inorganic composition of these sample types. An aqua regia digestion for gold is suitable for soils and sediments because the gold is expected to be largely available for chemical attack. The same cannot be said for an aqua regia digestion of rocks and drill cuttings where the gold may be retained in an insoluble quartz matrix or otherwise encapsulated. For rocks and drill cuttings, a fire assay fusion is clearly the superior method of gold analysis. The various ICP-MS packages offer an attractive mix of elements and detection limits but these packages are applicable only to soils, silts and lake and stream sediments because the detectors of a plasma mass spectrometer are easily saturated by even lightly mineralized material.