Metrohm 746 VA Trace Analyzer User Manual

Page 484

6.9 Content calculation

746 VA Trace Analyzer / 747 VA Stand

6-21

6.9.2

Dilution calculation

In all cases in which only part of the sample volume

V.sample

is added to the

measuring vessel or in which the sample is additionally diluted before or after addi-

tion to the measuring vessel (e.g. by addition of auxiliary solutions), instead of the

sought mass concentration

the effective mass concentration

eff,s

is measured in

the measuring vessel. The relation between these two quantities is given by the di-

lution factor f

eff,s

= f

eff,s

Effective mass concentration of the sample in the measuring vessel at
the time of measurement (shown only in the calibration curve)

Mass concentration of the sample
(=

Mass conc. on the "RESULTS/Evaluations" page)

Dilution factor

With the aid of the automatic volume bookkeeping of the 746 VA Trace Analyzer,

the dilution factor f

is recalculated continuously for every dilution step. In connec-

tion with the volume bookkeeping, the following points should be noted:

– At the start of a determination with the key, the volume

bookkeeping is automatically reset to 0.

– If work is carried out with

Auto.batch = on

(automatic series de-

termination), the volume bookkeeping at the end of the program is

reset to 0 only if the

RINSE

instruction is used.

– The

RINSE

instruction resets the volume bookkeeping to 0.

The simple addition of an auxiliary solution to a sample solution in a measuring

vessel will serve to illustrate the dilution calculation:

Sample

Measuring vessel

Auxiliary solution

DOS>M

SMPL>M

V.sample
m.sample

V0.sample = V.sample
m0.sample = m.sample
V.eff = V.sample + V.add

eff,s

= = f

eff,s

V.add

m.sample

V.eff

V.sample

V.eff

m.sample

m.sample
V.sample