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(a)
(b)
(c)
+
+
N
+
N
OH
[(CF
3
SO
2
)
2
N]
−
N
N
*
CH
3
R
1
X
−
Br
−
R
1
= C
2
H
5
, C
3
H
7
, C
4
H
9
, C
5
H
11
, C
6
H
13
, C
10
H
21
X
−
= BF
4
−
, PF
6
, NO
3
−
, CF
3
SO
3
−
, Br
−
, Cl
−
, CF
3
COO
−
,
CH
3
COO
−
(d)
(e)
*
OH
*
+
OH
N
N
+
X
−
: = Bis(trifluoromethylsulfonyl) imide NTf
2
−
X
−
X = Bis(trifluoromethylsulfonyl) imide NTf
2
−
O
O
F
F
−
O
O
F
F
F
S
N
S
F
−
F
S
N
S
F
F
F
O
O
F
F
O
O
(g)
(f)
O
NH
+
Br
−
N
+
O
NH
*
Br
−
O
OH
O
OH
(h)
(i)
R
4
−
N
+
X
−
+
Br
N
R
3
n-1
R
1
R
2
n = 19, 17, 15, 13
R
1
= R
2
= R
3
= R
4
= CH
3
, C
2
H
5
, C
3
H
7
, C
4
H
9
X = BF
4
−
Figure 10.1
The structures of primary classes of ionic liquids
[18].
Reprinted from [18] with permission from
Wiley-VCH Verlag GmbH & Co. KGaA © 2007.
Recently, application of SFC in drug and biosample analysis has been well-documented [43-60]. For a
green approach, SFC is a potential strategy for reduction of the organic waste. Unfortunately, SFC is not as
popular as LC in separation and purification science use until now.
10.3 Green instruments
The aim of the green instrument is to reduce the production of organic waste and maintain suitable separation
efficiency and sensitivity at the same time. For traditional liquid chromatography (LC), the flow rate of this
analytical-scale pump is usually over 1 ml min
−1
(the preparative-scale pump is ignored because the flow rate
of this kind of pump is faster than the analytical-scale pump). Some designs slow down the flow rate of the
