Thermo Scientific VSTAR-ISE, Справочное руководство

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Thermo Scientific Orion VERSA STAR pH/ISE/Temperature Module
Single Known Addition
A standard of known concentration is added to a sample of unknown concentration. The total concentration should
approximately double upon the addition of the standard, therefore sample concentration should be known within an
order of magnitude. Refer to the following table to choose the correct standard concentration and volume of addition.
• Refer to the appropriate electrode user guide for instructions for preparing the electrode, required
solutions (ionic strength adjusters, standards, etc) and any special requirements. Determine the
electrode slope as directed in the electrode user guide.
• Ensure that the electrode, ATC probe and reference electrode (if applicable) are connected to the
meter inputs that correspond with the selected channel.
Double Known Addition
For most double known addition analysis, it is recommended that:
• The sample volume should be 100 mL.
• The concentration of the standard added should be 100 times the expected sample concentration.
• Calculate the volume of standard required to halve the initial sample concentration and divide by
six. Five sixths of the volume will be added in the first addition and the remainder in the second. If
available, consult a printout from a previous analysis of a similar sample. Note: the proposed values for
constant mV will be smaller than those recommended for known addition. This is an effort to minimize
me chance of over "subtracting" the sample (overshooting the endpoint).
Refer to the appropriate electrode user guide for instructions for preparing the electrode, required solutions
(ionic strength adjusters, standards, etc) and any special requirements.
Ensure that the electrode, ATC probe and reference electrode (if applicable) are connected to the meter inputs that
correspond with the selected channel.
Amount of standard to be
added per 100 mL of sample
Standard concentration compared to expected
sample concentration
1 mL 100 times more concentrated
5 mL 20 times more concentrated
10 mL 10 times more concentrated