Basic HTML Version
N. Nagae, T. Enami and S. Doshi, LC/GC North America October 2002.
After stopping pump for 1 hour
1) N. Nagae, T. Enami and S. Doshi, LC/GC North America October 2002.
２
) T. Enami and N. Nagae, American Laboratory October 2004.
３
) T. Enami and N. Nagae, BUNSEKI KAGAKU, 53 (2004) 1309.
★
Sunniest RP-AQUA is a reversed stationary phase, so that
it is not wet with water. However the contact angle of water
on the surface of Sunniest RP-AQUA is less than that of a
conventional C18. Expelling force (pressure) acted by
capillarity on Sunniest RP-AQUA is less than atmospheric
pressure. So, Sunniest RP-AQUA shows reproducible
retention under 100% aqueous conditions.
Sunniest C18
Sunniest RP-AQUA
Sunniest C8
★
C18 and C8 reversed phases exhibit decreased and poorly
reproducible retention under more than 98% aqueous conditions
as shown in Fig. 1. This problem traditionally has been explained as
being the result of ligand collapse or a matting effect. Nagae
1-3
ascertained , however , that the mobile phase was being expelled
from the pores of the packing material under 100% aqueous
mobile phase conditions, as Fig. 2 shows.
◆
Reproducibility of retention under 100% aqueous conditions
★
When the surface of packing materials isn’t wet by water,
water used as a mobile phase expels from the pore of the
packing material by capillarity. This is a reason why
reproducibility in retention is low under 100% aqueous conditions.
Reversely pressure around the packing material makes water
permeate into the pore of the packing material to overcome a
force worked by capillarity.
In other words, the surface of a reversed phase like C18 isn’t wet
by water anytime even if water permeates into the pore of the
packing material or not. So it is wrong that we say “ dewetting”
when water expel from the pore. Saying “ Depermetating” is
more suitable.
10nm
Water
Silica
Pressure
Fig. 2 Schematic diagram of C18 particle
Stop flow
Water permeates
into the pore.
Permeating
Water expels from the
pore by capillarity.
Depermenating
Sunniest RP-AQUA showed more than 97% of
reproducibility in retention using 100% aqueous buffer as a
mobile phase.
Column: Sunniest RP-AQUA, 5
μ
m 150 x 4.6 mm
Mobile phase: 10mM Phosphate buffer pH7.0
Flow rate: 1.0 mL/min
Temperature: 40 ºC and 25ºC
Sample: 1 = Cytosine 2 = Uracil
3 = Thymidine 4 = Uridine
5 = Thymine
5
2
4
1
3
0
2
4
6
8
10
12
14
Retention time/min
1 2
3
4
5
40 ºC
25 ºC
0
10
20
30
40
50
60
70
80
90
100
1
2
3
4
5
Measurement number every stop flow
Relative retention of thymine (%)
Change of retention of thymine at 40 ºC
(measurement every stop flow for 1 hour)
◆
Separation of nucleic acid bases
Fig. 1 Retention behavior of a C18
column under 100% aqueous mobile
phase conditions
Website : www.chromtech.net.au E-mail : info@chromtech.net.au telNo : 03 9762 2034 . . . in AUSTRALIA