The accuracy and precision of the results obtained for total mercury in various environmental and biological samples and certified
reference materials (CRMs) by various analytical methods, including k0-instrumental neutron activation analysis (k0-INAA), radiochemical neutron activation analysis (RNAA) and cold vapour atomic absorption (and atomic fluorescence) spectrometry
(CVAAS/AFS) used in routine analysis in our laboratory, were investigated. Three natural matrix reference materials (RMs)
from the International Atomic Energy Agency (IAEA), five CRMs from the Institute for Reference Materials and Measurements
(IRMM), six CRMs from the National Institute of Standards and Technology (NIST) and one from the Jožef Stefan Institute (IJS)
were analyzed. The results obtained show good agreement between certified or assigned values, and between the methods used,
except for some data obtained by k0-INAA in biological samples. This can be explained by losses during irradiation in semi-open systems (irradiation in plastic
ampoules) and/or spectral interferences.