Influence of Sodium Bicarbonate Concentration on Retention Time (SI-90 4E)

Please use this column with suppressor type ion chromatography system.

The concentration of sodium bicarbonate (NaHCO₃) in eluent influences the retention of some anions
when analyzed by IC SI-90 4E
(a column for anions analysis). The relationship between sodium
bicarbonate concentration and anions’ retention time is shown below.
Elution volumes of anions from fluoride to nitrate are not influenced
considerably by the change in sodium bicarbonate concentration. While
retention volumes of later eluting anions (phosphate and sulfate) are
shorten by increasing the sodium bicarbonate concentration. At
concentration ~5 mM, phosphate ion peak coelutes with carbonate ion
peak.

Sample : 20?L
F^– 2mg/L
Cl^– 3mg/L
NO₂^– 5mg/L
Br^– 10mg/L
NO₃^– 10mg/L
HCO₃^– 300mg/L
PO₄^3- 15mg/L
SO₄^2- 15mg/L
I^– 10mg/L

Column       : Shodex IC SI-90 4E (4.0 mm I.D. x 250 mm)
Eluent       : 1.8 mM Na2CO3 + NaHCO3 aq.
Flow rate : 1.0mL/min
Detector : Suppressed conductivity
Column temp. : 25 °C