Instruction Manual

3 General settings for exploratory and determination mode

797 VA Computrace – Software

PSA – Potentiometric Stripping Analysis

General:

PSA or Potentiometric stripping analysis with chemical oxi-

dation is mainly used to determine substances in an organic matrix

with the aid of mercury film electrodes without prior digestion. The

PSA measurement mode can be set for the exploratory and deter-

mination mode by selecting PSA - Potentiometric stripping analysis

for the Mode parameter in the EXPLORATORY SPECIFICATION or

WORKING METHOD SPECIFICATIONS window.

Description:

In PSA measurement mode, the analytes are deposited at the work-

ing electrode with the constant Deposition potential during a pre-

determined Deposition time. Then the applied deposition potential

is switched off and the voltage U is measured as a function of the

time t with a sampling rate of 69.69 kHz. The measurement time is

limited either by the set Potential limit or the Maximum time. The

voltage measurement U vs t is used to calculate the retention times

dt/dU vs U. This results in peak-shaped curves which can be evalu-

ated. The Peak voltage is characteristic of the substance, the Peak

area

is proportional to its concentration.

Deposition potential

Deposition time

Potential limit

Maximum time

dt/dU

Peak voltage

Peak

area