IonPacAS9-SC
034656-06
Page 12 of 28
eluents or can be used as a column regenerant.
D.
AS4A Sodium Carbonate/Bicarbonate Concentrate (100X)
0.18 M Na
2
CO
3
/0.17 M NaHCO
3
1.
Order DIONEX P/N 039513
or
2.
Thoroughly dissolve 19.078 g of Na
2
CO
3
and 14.282 g of NaHCO
3
in 700 mL of deionized water with a
specific resistance of 18.2 megohm-cm. Dilute to a final volume of 1,000 mL.
CAUTION
Do not use hydroxide eluents or hydroxide to adjust the pH of any eluent higher than pH 11 to effect
selectivity changes. Using eluents with pHs greater than 11 may cause irreversible damage to the IonPac
AS9-SC/AG9-SC Columns.
4.4.2 Preparation of Carbonate Eluents
A. Eluent: 2.0 mM Carbonate/0.75 mM Bicarbonate
Make the eluent by pipetting 10.0 mL of the eluent concentrate into a 1 L volumetric flask. (100X concentrate = 200
mM Na
2
CO
3
/75 mM NaHCO
3
.).
See Section 4.1, Preparation of Eluent Concentrates for the preparation of the 100 x
eluent concentrate. Use degassed, deionized water with a specific resistance of 18.2 megohm-cm to dilute the
concentrate to a final volume of 1,000 mL.
4.4.3 Preparation of Borate Eluents
A. Eluent : 22 mM H
3
BO
3
/22 mM Na
2
B
4
O
7
Thoroughly dissolve 8.391 g Na
2
B
4
O
7
/10 H
2
O (MW 381.42 g/mole) plus 1.360 g H
3
BO
3
(MW 61.84 g/mole) in 700
mL degassed, deionized water with a specific resistance of 18.2 megohm-cm in a 1 L volumetric flask. Dilute to a final
volume of 1,000 mL.
B. Eluent Preparation for Gradient Program
1.
Eluent : 10 mM H
3
BO
3
/10 mM Na
2
B
4
O
7
Thoroughly dissolve 3.814 g Na
2
B
4
O
7
?10 H
2
O (MW 381.42 g/mole) plus 0.618 g H
3
BO
3
(MW 61.84 g/mole) in
700 mL degassed, deionized water with a specific resistance of 18.2 megohm-cm in a 1 L volumetric flask. Dilute
to a final volume of 1,000 mL.
2.
Purge: 50 mM H
3
BO
3
/50 mM Na
2
B
4
O
7
Thoroughly dissolve 19.071 g Na
2
B
4
O
7
?10 H
2
O (MW 381.42 g/mole) plus 3.092 g H
3
BO
3
(MW 61.84 g/mole)
in 700 mL degassed, deionized water with a specific resistance of 18.2 megohm-cm in a 1 L volumetric flask.
Dilute to a final volume of 1,000 mL.
4.5
The Borate Eluent System
The borate eluent system gives the same elution order on the AS9-SC column as the carbonate eluent system (see Figure 4, Anion
Separation using 22 mM Borate Eluent). However, the borate anion is a weaker “pusher” ion than carbonate. Therefore a higher
concentration borate eluent is required to provide the same elution times observed with a carbonate eluent system. The major
advantage of the borate system is that early eluting ions (i.e., fluoride, nitrate) can be easily spread out thus improving resolution
simply by using a more dilute eluent (see Figure 5, Anion Separation using 10 mM Borate Eluent with Column Purge after Nitrate).
Carbonate eluent systems can also be diluted to produce a similar effect but not as reliably due to carbon dioxide intrusion from
the air. This improvement in resolution is especially beneficial when doing sub-ppm determinations of early eluting ions such as
chlorite and bromate in the presence of high amounts of common anions such as fluoride and chloride.
