General Catalog

Professional IC Systems
Sequential Suppression
Sequential suppression is the combination of chemical
suppression using the «MSM II» with Metrohm CO 2
Suppression «MCS». In this way anions can be detected
with carbonate/ bicarbonate eluents at the low background
conductivity of hydroxide eluents.
The removal of the CO 2
prevents the carbonate equilibrium
from negatively affecting the peak areas. The
benefit for the user: Peak areas thus obtained are up
to 50% larger – at the same concentration and for
the same sample volume; this means lower detection
limits.
No carbonate peak also means no annoying interference
with the quantification of certain analyte anions.
For example, chloride and carbonate coelute on
many polystyrene-divinylbenzene columns. By using the
CO 2
suppressor such problems are a thing of the past.
The virtual elimination of the injection peak improves
the determination of rapidly eluting anions, for example
fluoride. Although the separation of the injection
peak and fluoride peak is already very good on polyalcohol
columns, the detection limits can be improved
even further by using the CO 2
suppressor. As the injection
peak is practically no longer visible, considerably
larger sample volumes can also be injected.
Drinking water from Herisau (Switzerland): comparison of suppression with
«MSM II» alone (black) and with «MSM II» plus «MCS» (red).
Column: Metrosep A SUPP 5 – 100 (6.1006.510)
Eluent: 3.2 mmol/L Na 2
CO 3
; 1.0 mmol/L NaHCO 3
Flow rate: 0.7 mL/min
Nr. Ion Conc. (mg/L)
1 Injection peak –
2 Fluoride 0.04
3 Chloride 7.79
4 Carbonate –
5 Bromide 0.004
6 Nitrate 7.82
7 Sulfate 5.20
25 — IC