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AOAC RESEARCH INSTITUTE
AOAC
OFFICIAL METHODS OF ANALYSIS
(OMA)
OMAMAN-28/AOAC 2006.03
Study Director: Sharon Webb, University of Kentucky, Division of Regulatory Services,
103 Regulatory Services Bldg, Lexington , Kentucky 40546-0275
2006.03 results. Two examples can be made with concern to cobalt and nickel (Group A).
a) Cobalt. Material ‘P’, result: 0.52 vs 0.57 (collaborative study), RSD = 20.46 vs 66.74
(collaborative study)
b) Nickel. Material ‘P’, result: 38.90 vs 33.39 (collaborative study), RSD = 3.89 vs 13.42
(collaborative study).
In general, RSD for Group B metals remain low enough.
Comparability
Comparability to AOAC 2006.03 for Group A elements has been calculated by testing 15 of the
original collaborative study materials with both digestion methods. Data are expressed as a
percentage recovery of the original grand average result. Many results show higher recovery
values. Probably, these results demonstrate the enhanced recovery “power” of the proposed
method, on the basis of RDS values.
Working Range
The working range of the method is determined by the working calibration standards. Each
laboratory should determine the range best suited to their instrument’s capability. In general,
10 % extrapolation from the highest calibration standard often produces acceptable results for
Group A and B elements.
LOD and LOQ
With reference to Group A, the paper shows the instrument LOD (estimated with standard
solutions) and the method LOQ and LOD (estimated with validation materials).
Interestingly, the LOQ for Group B elements are completely dependent upon the calibration
range since the method is not working close to the instrument limits.
Ruggedness trial
Generally, results have not shown appreciable effects from the deviations of the method.
Obtained results (differences) are all within normal variation and indicate that the method is
sufficiently rugged with respect to the conditions studied.
ER 9
Significant work was done and data generated; information presented well. Method presents a
step forward in speed, safety and scope. Digestion is relatively simple and straightforward, with
few chances for human error beyond sample weight. Updating the instrumentation to ICP-OES
is very important. Scope and ranges are well covered by the materials used. Digestion options
are well researched.
ER 10
Robust Method
Cons/Weaknesses of the Manuscript:
ER 1
Some of the optimization steps are dated and based on studies from 30 years ago. System
hardware and performance has changed and this needs to be considered. I.E. Meremt's
robustness test is a guideline for plasma conditions BUT NOT for analytical optimization of the
method/ICP. Also, Cs is a buffer for consideration on Axial/DV/TI systems, it is not typically used
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