Instrumentation
All 14C measurements at Metabolic Solutions,
Inc are made on a Packard 2100TR Liquid Scintillation
counter.
System Calibration
A third party independently calibrates
the system every six months. Additionally, a minimum
of once every twenty-four hours the system automatically
adjusts each photomultiplier tube to balance its response
to sample activity and calibrate the spectrum analyzer
in keV (a process called self-normalization).
System Validation
The system has been validated with respect to
accuracy, intra-run precision, inter-run precision
and stability.
The following values were established for each validation parameter:
Accuracy:
High
level control = within 0.10%
Low
level control = within 0.19%
Intra-run Precision:
High
level control = 0.11%
Low
level control = 0.22%
Inter-run Precision:
High
level control = 0.33%
Low
level control = 0.42%
Stability: Prepared
breath samples (hyamine trapped CO2)
are stable for two weeks.
System Monitoring
During each run, three (3) commercial
controls (background, low level and high level) are
assayed three times and a mean calculated. All
samples must be within 2SD for the run to be acceptable.
The mean values, standard deviations and 2SD range are
shown below for these three system monitoring controls:
| Sample |
Mean (dpm) |
SD (dpm) |
Range (dpm) |
| Background |
41.8 |
2.1 |
37.6-46.0 |
| Low Level Control |
42615 |
181 |
42253-42977 |
| High Level Control |
129216 |
423 |
128370-130062 |
|
