Sample:
1 = Uracil (0.07
µ
g)
2 = Propranolol (1.53
µ
g)
3 = Nortriptyline (0.32
µ
g)
4 = Amitriptyline (0.32
µ
g)
Mobile phase: Acetonitrile/
10mM acetate ammonium pH6.8
=(40:60)
Mobile phase: Acetonitrile/
20mM phosphate buffer pH7.0
=(60:40)
Loading capacity of amitriptyline as a basic compound
Amitriptyline overlords much more at acetonitrile/buffer mobile phase than methanol/buffer. Three kinds of core shell C18s were
compared loading capacity of amitriptyline at three different mobile phases.
Common condition: Column dimension,150 x 4.6 mm, flow rate; 1.0 mL/min, temperature; 40
o
C
100 times
30 times
SunShell C18
Brand D C18
1
2
3
4
1 2
3
4
Brand D C18
SunShell C18
1
2
3
4
1
2
3
4
1
3
4
6
4.4%
Theoretical plate was calculated by 5
σ
method
using peak width at 4.4% of peak height.
Mobile phase: Acetonitrile/
0.1% formic acid
=(30:70)
USP tailing factor
3.6
2.9
2.4
1.8
1.3
Amitriptyline overloads at low weight
when acetonitrile/0.1% formic acid
mobile phase. A peak is shifted
forward under overloading.
Brand D C18 overloaded at more than 0.01
µ
g of amitriptyline while SunShell C18 overloadsed at more than from 0.3 to 1
µ
g of amitriptyline.
Surprisingly loading capacity of Brand D C18 was only one hundredth to compare with SunShell C18 under acetonitrile/20mM phosphate buffer
pH7.0=(60:40) mobile phase. Brand E C18 always showed poor peak of amitriptyline.
7 times
0 1 2 3 4 5 6 7 8 9 10
Retention time/min
Brand E C18
1 2
3
4
0 1 2 3 4 5 6 7 8 9 10
Retention time/min
Brand E C18
1
2
3
4
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