Thermo orion 410Aplus, Инструкция по эксплуатации

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Benchtop pH/ISE Meter Instruction Manual
Other Measurement Modes 47
Double Known Subtraction Measurement Procedure
In double known subtraction, each addition of standard subtracts an
increment of the species to be measured. The procedures and meter
prompts are the same as for double known addition except the meter
prompts for the reaction ratio. Enter the ratio at the meter prompt, then
continue as usual.
Take care that subtraction ability of chosen standard concentration and
volume added does not exceed the concentration of sample.
For most double known subtraction analysis, it is recommended that:
a. Sample volume be 100 mL.
b. The concentration of the standard added be 50 times the expected
sample concentration.
c. The volume of the first addition of standard be 1 mL.
d. The volume of the second addition of standard be 10 mL.
NOTE: Make sure the correct reaction ratio of sample
to standard is entered.
For example: A sulfide (S = ) sample is to be subtracted by the addition of
silver (Ag + ). Two Ag + ions are required to subtract one S = ion, therefore the
reaction ratio is 0.5.