Ground humus samples weighing 6 to 15 g are compressed under 30 tons of pressure to form a briquette (smaller samples are weighed in vials). Smaller samples will be weighed into vials. Briquettes are stacked with flux wires and two internal standards (up to 28 samples) and irradiated along with flux wires at a thermal neutron flux of 7 x 10 12 ncm-2 s-1. After a 7-day period to allow Na-24 to decay the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires and control standards, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. For values exceeding the upper limits, assays are recommended. Duplicates are analyzed when sample material is available.
Required Preparation: B1 (drying and blending humus)
Elements and Detection Limits (ppm)
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.