2.3. Mineral determination
2.3.1. Instrumental neutron activation analysis (INAA)
For the short half-life group, the homogeneous sample was
accurately weighed (appropriately 50–100 mg) and sealed in
cleaned polyethylene vials. These containers were put into a
polyethylene bottle (Rabbit) for irradiation. For medium half-life
and long-life groups, each sample was sealed in clean polyethylene
bags. These containers were put into polyethylene tubes for
medium irradiation and in aluminium cans for long irradiation.
Samples were irradiated in an open pool type Thai Research
Reactor (TRR-1M1) at the Thailand Institute of Nuclear Technology
(TINT), Bangkok. The concentration of each element was obtained
by comparison with various certified reference materials (Rice
flour, NIST 1568a, USA; Dog fish muscle and liver, ACSP DORM-1,
National Research Council, Canada; Marine sediment, NMIJ 7302-a,
National Metrology Institute of Japan) and standards. Short,
medium and long irradiations were performed in order to
determine as many elements as possible using the following
conditions: