DNAPac PA200
Document No. 065036
Page 17 of 25
5.7.2 Selectivity in Sodium Perchlorate (NaClO
4
) Gradients
When NaCl eluent is replaced with NaClO
4
(see below), the retention differences are less pronounced, and the
effect of pH on retention is also reduced. However, all of the ODNs with 3’ base substitutions are again
resolved, and those with 5’ substitutions are at least partially resolved, at pH 9 or 10. Addition of solvent to
NaClO
4
eluent will reduce retention and minimize hydrophobic interactions, resulting in smaller selectivity
changes due to terminal base differences at these pH values.
CHART 9 Effect of pH on Retention (by Terminal Base):
5 mM/mL NaClO
4
gradient, 0% CH
3
CN, 5’X-G
6
C
3
A
5
T
9
-Y3’, pH 9-11
7
8
9
10
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G
pH 9
pH 10
9.5
10.5
11.5
12.5
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G
pH 11
13
14
15
16
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G
7
8
9
10
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G
pH 9
pH 10
9.5
10.5
11.5
12.5
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G
pH 11
13
14
15
16
-1
99
mAU
Time (min)
7
6
5
4
3
2
1
Flow: 1.20 ml/min
X=C, Y=A
X=A, Y=A
X=T, Y=A
X=G, Y=A
X=C, Y=T
X=C, Y=C
X=C, Y=G