Thermo Scientific 9609BNWP, Руководство пользователя

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23 Fluoride Ion Selective Electrode User Guide
Single Known Addition
Known addition is a convenient technique for measuring samples
because no calibration curve is required. It can be used to
verify the results of a direct calibration or to measure the total
concentration of an ion in the presence of a large excess of a
complexing agent. The sample potential is measured before and
after addition of a standard solution. Accurate measurement
requires that the following conditions be met:
• Concentration should approximately double as a result of
the addition.
• Sample concentration should be known to within a factor
of three.
• Either no complexing agent or a large excess of the
complexing agent may be present.
• The ratio of the uncomplexed ion to complexed ion must
not be changed by addition of the standard.
• All samples and standards should be at the same
temperature.