Investigation of the element content of black shale samples by INAA and EDXRF

Over 50 elements in black shale samples SChS-1A and SLg-1A were measured using instrumental neutron activation analysis and energy dispersive X-ray fluorescence for repeated interlaboratory comparison tests. The mean values and standard deviations for a confidence probability of 0.95 were calculated for 9 parallel aliquots. The relative error stays below 10% for most elements, and in many cases, the measured contents match their initially certified values within the uncertainties. It is shown that 100 mg aliquots are not representative for determining the gold content in the investigated samples. The results obtained can be used for additional certification of these samples.