Metrohm 757 VA Computrace - Manual (Page 189)

8.6 Voltammetric problems
757 VA Computrace – Software
179
Calibration with chemically non-isoformal standards
With both possible calibration techniques, it must be ensured that
the standards used for calibration are chemically isoformal with
the analytes. The standard substances must therefore have the
same valency (e.g. with Fe, Al) or complex formation form (e.g.
with As, Cr, Se) as the substances already present in the analysis
solution. If this is not the case the calibration can produce com-
pletely wrong results owing to the different peak voltages and
sensitivities.