RNAA
Definition
Radiochemical Neutron Activation Analysis. After irradiation, the analyst chemically separates the isotope of interest to remove interfering activity. More sensitive, destructive.
- Full name
- Radiochemical Neutron Activation Analysis
- Key step
- Chemical separation of the isotope of interest after irradiation
- Purpose of separation
- Removes interfering activity from other activated elements
- Sample effect
- Destructive
- Compared to INAA
- More sensitive, but consumes the sample
Common questions
Why perform chemical separation after irradiation rather than before?+
Irradiating first converts the target element to a detectable radioisotope; separating afterward isolates that isotope from the bulk matrix and other activated elements, improving the signal without needing pre-irradiation purification.
When would a lab choose RNAA over instrumental NAA (INAA)?+
RNAA is chosen when trace elements are present at concentrations too low to resolve against a complex gamma-ray background, since removing interfering activity chemically gives a cleaner spectrum than counting the whole sample.
What is the practical drawback of RNAA compared to INAA?+
It destroys the sample during chemical processing and requires specialised radiochemistry handling, making it slower and less suited to cases where the evidence sample must be preserved intact.
Related terms
- BARC Trombay
- Bhabha Atomic Research Centre, Mumbai. Hosts the Dhruva and Apsara-U research reactors that have historically supplied neutron flux for Indian NAA work.
- Gamma Spectrometry
- Energy-resolving detection of gamma rays. Each radioisotope emits a characteristic gamma at a known energy, which is how NAA identifies elements.
- Half-Life
- The time required for half the radioactive atoms in a sample to decay. Set by the decay constant lambda through t1/2 =...
- HPGe Detector
- A high-purity germanium semiconductor crystal cooled with liquid nitrogen to about 77 kelvin. Resolution at the 1,332 keV gamma line of cobalt-60...
- INAA
- Instrumental Neutron Activation Analysis. The whole sample is irradiated, cooled, and counted directly. No wet chemistry. Non-destructive.
- Neutron Capture (N, Gamma)
- The reaction in which a stable nucleus absorbs a neutron and becomes a radioactive isotope of the same element, emitting a prompt...
- Thermal Neutron
- A low-energy neutron (around 0.025 eV) that has been slowed by a moderator. The workhorse particle of NAA because slow neutrons are...