Metrohm VoltIC pro I - Manual (Page 15)

Application Bulletin 356
Installation instruction for «VoltIC pro I»
Page 15 of 18
The recalculation to the actual sample volume used (Value
1) takes place after the VA analysis in MagIC Net TM .
Therefore, your sample table might look like the following
one:
Fig.: Sample table excerpt showing the use of «VoltICpro.imet»
For evaluation and after recording the first chromatogram,
check the retention times of your compounds. Since they
depend on the performance of your column, you may have
to adjust them in your method.
4 Exemplary measurement
An exemplary measurement was performed, including the
ions fluoride, chloride, nitrite, bromide, nitrate, phosphate,
sulfate, lithium, sodium, ammonium, potassium, calcium,
and magnesium (1000 µg/L each), zinc, cadmium, lead and
copper. Anions and cations were measured from separate
sample vials with the sample for cation measurement being
acidified with 50 µL nitric acid (2 mol/L) per 50 mL sample.
The two following chromatograms were recorded in parallel.
Fig.: Standard chromatogram cations, 1000 µg/L
Fig.: Standard chromatogram anions, 1000 µg/L
For the calibration, the average peak areas of 3 injections
were evaluated. Within the concentration range of 20 – 1000
µg/L, a quadratic curve type was used for evaluation of
anions, and a linear curve type was used for evaluation of
cations. Correlation coefficients and standard deviations are
listed in the following table. The calibration curves for
chloride and sodium are shown as examples.
Correlation
coefficient
Relative standard
deviation [%]
Lithium 0.999984 0.761
Sodium 0.999947 1.347
Ammonium 0.999939 1.371
Potassium 0.999776 2.904
Calcium 0.999864 1.813
Magnesium 0.999973 0.890
Fig.: Statistical data of a six-point cation calibration from 20 µg/L to
1000 µg/L
Correlation
coefficient
Relative standard
deviation [%]
Fluoride 0.999954 1.594
Chloride 0.999988 0.786
Nitrite 0.999992 0.650
Bromide 0.999993 0.584
Nitrate 0.999993 0.587
Phosphate 0.999997 0.408
Sulfate 0.999992 0.616
Fig.: Statistical data of a six-point anion calibration from 20 µg/L to
1000 µg/L
Fig.: Chloride calibration curve from 20 µg/L to 1000 µg/L