Peak on highly curved baseline, Peak overlapping – Metrohm 797 VA Computrace User Manual

Page 285

9.6 Voltammetric problems

797 VA Computrace – Software

273

Analysis solution:

25 μg/L Cu; 10 μL HCl 30%

Standard addition:

with 250 ng Cu

Electrode:

HMDE (enrichment 90 s at –600 mV)

Peak on highly curved baseline

If peaks lie on a highly curved baseline, the first attempts at rectifi-
cation should involve chemical or measurement technique coun-
termeasures to eliminate the adverse effect on the peak evaluation
due to the highly curved baseline. Such measures include longer
purging times

(see Oxygen interference, section 9.6),

changing the

pH value, changing the supporting electrolyte concentration, modi-
fying or changing the supporting electrolyte, use of complexing
agents

(see Complex formation, section 9.6),

longer

deposition

times and changing the measurement technique.

If the curvature of the baseline can not or only partially be elimina-
ted by the above measures, the 797 VA Computrace offers the pos-
sibility to approximate a curved baseline by selecting

Polynomial

Exponential

for the baseline

Type

(see Baseline, section 5.2).

A further possibility to evaluate peaks on curved baselines involves
the background subtraction after measuring a blank solution, in
particular when the curved baseline can be clearly attributed to the
supporting electrolytes

(see Determination, section 5.2).

Peak overlapping

If the peak overlapping has reached a critical level at which the cal-
culated peak height or peak area is falsified by the neighboring
peak, it is advisable to take the overlapping into account by a
change in the baseline calculation. For this, select the

Front end

Rear end

option for the baseline

Scope

(see Baseline, section 5.2).

CuCl

2–

CuCl

–

CuEDTA