
I-5
General Information
Thermo Scientific Orion 2111LL Sodium Monitor User Guide
ROSS and the COIL tradedress are trademarks of Thermo Fisher Scientific Inc. US Patent 6,793,787
Principles of
Calibration
Calibration .procedures .for .an .analytical .instrument .are .important .and .must .
be .performed .carefully . . .The .calibration .procedure .used .in .the .Thermo .
Scientific .Orion .2111LL .is .a .variation .of .Double .Known .Addition .(DKA) .
using .ROSS .Ultra® .electrode .technology .and .patent-pending .flow .cell .
technology .in .combination .with .the .passive .diffusion .system . . .This .method .
has .the .distinct .advantages .of .being .fast, .easy, .and .accurate .
Before .calibration .begins, .the .diverter .valve .is .turned .to .divert .flow .from .
the .measure .drain .to .the .re-circ .tube, .allowing .the .flow .cell .to .fill . .
The .two .air .valves .serve .dual .purposes .during .the .calibration .sequence .
The .first .function .is .to .stop .the .airflow .through .the .sample, .and .redirect .
the .airflow .to .the .headspace .of .the .flow .cell . . .Thus, .the .flow .cell .is .filled .
without .causing .air .bubble .disturbance .in .the .sensing .tube . . .The .second .
function .ensures .proper .siphoning .operation . . .The .combination .of .these .
functions .provides .an .accurate .volume .for .calibration .
At .the .first .step .of .the .DKA .calibration .the .actual .concentration .in .the .
sample .is .unknown . . .The .instrument .measures .the .potential .(E
s
) .and .stores .
this .value .in .the .microprocessor . . .A .known .amount .of .standard .1 .solution .
is .added .to .the .flow .cell, .which .increases .the .concentration .(C
s
) .with .a .
corresponding .known .amount .(dC
1
) . . .During .this .process, .air .is .pumped .
into .the .re-circ .tube, .thoroughly .mixing .sample .and .standard .in .a .closed-
loop .system . . .The .new .potential .(E
1
) .is .measured .and .stored .automatically .
when .stability .is .reached . . .Adding .standard .2, .preferably .10 .times .more .
Siphon Tube
Siphon Drain
Sensing Tube
Double-Known
Addition (DKA)
Figure I-
Flow Cell Volume for DKA
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