4 optimization of the measuring potential, Optimization of the measuring potential, Figure 6 – Metrohm 871 Advanced Bioscan User Manual

Page 27: 4 optimization of t, He measuring potential

3.4 Optimization of the measuring potential

871 Advanced Bioscan / Instructions for Use 8.871.1003

3.4

Optimization of t

An optimization of

may bring benefits
a) The sensitivity

against the bac

vity

peak overlappi

optimally separ

If there are no suita

mogram is require

the given potential

dividual chemical s

ces.

here are two different types of voltammograms, each of which is suit-

ynamic voltammogram

and a scan voltammogram.

ch a hydrodynamic voltammogram:

he measuring potential

the measuring potential for amperometric detection

in the following situations:

of the detection of the analyte is to be increased

kground signal.

b) The selecti

of the detection is negatively affected by the analyte

ng with a second substance peak that has not been

ated by chromatography.

ble literature data available, recording of a voltam-

d. This is a curve showing the relationship between

and the measured current. It is characteristic for in-

ubstances or even whole classes of substan

able for solving a different problem: a hydrod

A hydrodynamic voltammogram is made of several chromatograms

recorded in the DC mode. This involves recording a chromatogram of

the substance under investigation, dissolved in eluent, at a constant po-

tential. The potential is now varied several times and the process is re-

peated. Finally the height of the current peak obtained is evaluated and

plotted against the particular potential. Figure 6 shows a schematic ex-

ample of su

Figure 6: Example of a hydrodynamic voltammogram of a substance (A)

with the additional presentation of the measured values for the
pure eluent (B)

This method is recommended if the analyte is not present in a pure

form. It also provides more realistic information about the signal/noise

ratio and the selectivity towards overlapping peaks.
The scan voltammogram is recorded in the scan mode. The measur-

ing potential is varied backwards and forwards between two given limits

rent is then measured for each potential.

t a separation column

connected. If you work on trace concentrations of your analyte and

while the analyte is passed through the measuring cell. The actual cur-

The substance under investigation can be dissolved in the IC eluent

used (e.g. 10 ppm Sucrose in 0.1 M NaOH) and a larger amount (e.g.

100 mL) pumped through the flow cell withou