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6. Precision control and
assurance
See Fig. 1
for an overview.
Record the operations as follows. If any item to be recorded
lacks, specify the reason and, if possible, remove the cause and
retry the operation.
1) Establish a standard analytical procedure.
2) Sampling: Record the date and location of sampling,
operator's name, containers for sampling, sampling methods,
containers for transport and storage, and method of storage.
3) Sample check and acceptance at laboratory: Record the date
and location of sample check, operator's name, transportation
method, state of the sample, place and method of storage, and
control number. if a transport service is employed, keep a copy
of the invoice.
4) Reagents: Record the manufacturer's name, product name, lot
number, purity, shelf life, date of purchase, and supplier's
name of the standard samples and reagents used. For reagents
prepared in the laboratory, record the situation, including the
date and place of preparation, operator's name, and history of
use.
5) Instruments: Keep records of use (environments and
conditions), routine maintenance, sensitivity (evidences of the
required sensitivity in specific measurements, e.g.
chromatograms), inspection and repair.
6) Analysis: Record the date, place and environment of each
analytical step, operator's name, name and quantity of the
sample analyzed, order of measurement, and name and quantity of
reagents used.
7) Record the final solvent blank, entire operation blank, and
repetitions (from one and the same vial or from sampling).
8) Isotope ratio of the standard sample for measurements
involving isotopes: Record an evidence that the response ratio
of the two monitor ions for each compound in the standard
samples measured is in agreement with the theoretical value. The
experimental ratio should be within ±30% of the theoretical
ratio.
9) Chromatograms: Keep chromatograms related to standard
solutions, final solvent blanks, entire operation blanks and
samples.
10) Calculations
- Calculation process: Keep records that permit to trace the
entire process of calculations ranging from sampling to the
analyte concentration, including standard solution
concentration, quantity of the internal standard added, area
measured on the instrument, etc.
- Recovery ratio: Check and record the recovery ratio, which
should preferably be in a range of 70 to 120%.
11) Blank tests
- Perform blank tests for the sampling tools and containers for
sampling, transportation and storage. Record the results.
- Perform blank tests for reagents every time a reagent of a new
lot number is used. Record the results.
- Entire operation blank: Perform a blank test in the same way
as in the analysis of the sample. Record the results.
12) Repetition: It is desirable to perform more than one time
the analysis for ten samples. The results of the repeated
measurements should preferably be in agreement within a range of
±30%. (This does not apply to analytes for which the observed
concentration is lower than ten times the target detection
limit.)
13) Intercalibration with other laboratories is recommended.
7. Miscellaneous
See also the Guidance for Operations in Food Sanitation
Laboratories established according to the Food Sanitation Act. |
