Supporting Information
Synthesis
of
1-[3-(N-pyrrole)propyl]-3-[1-tert-butoxycarbnylamino-propyl]
-imidazolium tetrafluoroborate ionic liquid for application in electrochemical
sensing of magnolol
Guishen Liu1, Yanhui Ma2, Xiao dong Hou1, Yina huang1, Jianpeng Chen1, Guoqing Zhan2, Chunya Li2,*
1 Chaozhou Quality and Measurement Supervision and Inspection Institute, Chaozhou 521011, China
2 Laboratory of Analytical Chemistry of the Satate Ethnic Affairs Commission, College of Chemistry and
Materials Science, South-Central University for Nationalities, Wuhan 430074, China
*Corresponding author. E-mail:lcychem@163.com
Table S 1 Comparison of analytical characteristics of the polymerized ionic
liquid film electrode for magnonol determination with other
electrochemical methods.
Electrode
Technique
Conditions
Linear range
(μmol
Polymerized
3-[1-butoxycarbnyl
Differential pulse
Phosphate buffer
voltammetry
pH 10.0
Differential pulse
Phosphate buffer
voltammetry
pH 7.0
Differential pulse
Phosphate buffer
voltammetry
pH 6.5
Differential pulse
Phosphate buffer
voltammetry
pH 6.0
Differential pulse
Phosphate buffer
voltammetry
pH 7.0
Reduced graphene oxide–wrapped WO3
Differential pulse
Phosphate buffer
nanowire modified glassy carbon electrode
voltammetry
pH 6.5
amino-propyl]-1-[3-(N-pyrrole)propyl]imidazoli
L-1)
0.05 – 10.0
Detection limit
(μmol
Ref.
L-1)
0.23
This
method
um tetrafluoroborate ionic liquid film electrode
Mesoporous Al-dopedsilica modified electrode
Mesoporous SiO2-modified carbon paste
electrode
Acetylene black nanoparticle-modified
electrode
Multiwalled carbon nanotubes modified
glassy carbon electrode
Multi-walled
carbonnanotubes
/poly(3,4-ethylenedioxythiophene)
Linear
sweep
Phosphate buffer
voltammetry
0.075 – 20.0
0.025
[1]
0.075 – 0. 75
0.038
[2]
0.038 – 0. 98
0.0188
[3]
0.019 – 3.76
0.00751
[4]
0.01 – 20.0
0.008
[5]
0.01 - 25
0.003
[6]
pH 7.0
core-shell nanofibers
References
[1] Liu T, Zheng XJ, Huang W S, Wu K B (2008) Voltammetric detection of
magnolol in Chinese medicine based on the enhancement effect of mesoporous
Al/SiO2–modified electrode. Colloids and Surfaces B: Biointerfaces 65: 226 –
229.
[2] Zhao J, Huang W S, Zheng X J (2009) Mesoporous silica-based electrochemical
sensor for simultaneous determination of honokiol and magnolol. Journal of
Applied Electrochemistry 39: 2415–2419.
[3] Yang X F, Gao M M, Hu H D, Zhang H J (2011) Electrochemical detection of
honokiol and magnolol in traditional Chinese medicines using acetylene black
nanoparticle-modified electrode. Phytochemical Analysis 22: 291 – 295.
[4] Huang W S, Gan T, Luo S J, Zhang S H (2013) Sensitive and selective
electrochemical sensor for magnolol based on the enhancement effect of
multiwalled carbon nanotubes. Ionics 19: 1303 – 1307.
[5] Huang M, Wu Y, Hu W B (2014) A facile synthesis of reduced graphene
oxide-wrapped WO3 nanowire composite and its enhanced electrochemical
catalysis properties. Ceramics International 40: 7219 – 7225.
[6] Zhang K X, Xu J K, Duan X M, Lu L M, Hu D F, Zhang L, Nie T, Brown K B
(2014) Controllable synthesis of multi-walled carbonnanotubes /poly(3,4
-ethylenedioxythiophene) core-shell nanofiberswith enhanced electrocatalytic
activity. Electrochimica Acta 137: 518 – 525.
Scheme S 1. Synthetic route of 3-[1-butoxycarbnyl amino-propyl] -1-[3-(N
-pyrrole)propyl]imidazolium tetrafluoroborate ionic liquid.
NH2
O
N
+
N
O
O
O
N
N
H
N
O
Br
N
NaBF4
O
N
+
N
N
BF4-
N
H
O
Scheme
S
2
Mechanism
for
the
polymerization
of
1-[3-(N-pyrrole)propyl]-3-[1-tert-butoxycarbonylamino-propyl]imidazolium
tetrafluoroborate ionic liquid.
N
-e-H+
*
N
R
R
*+
*
N
N
N
N
R
R
R
R
+
-e-H+
*
N
N
N
R
R
R
+
*
N
N
(n-3) N
N
R
R
R
R
N
N
N
R
R
R
-e-H+
N
N
(n-2) N
R
R
R
O
R=
N
+
N
BF4-
N
H
O
Scheme S 3. Mechanism for the oxidation of magnolol at the polymerized ionic
liquid film electrode.
O
O
OH
-e-H+
OH
OH
OH
O
O
O
-
-e
-H+
O
O
O
Coupling of free radicals
Polymer
It has been demonstrated that the electrochemical oxidation of phenolic compounds
via one-electron or two-electron transfer would generate phenoxy radical, or
phenoxonium ion and quinone, respectively [34-38]. It will be reasonable to deduce
that the electrochemical oxidation mechanism for magnolol could be attributed to the
aromatic-ring oxidation to form quinone and phenoxy radical. Subsequently, the
generated radicals undergo chemical reactions or a free radical polymerization
through C–O, C–C and/or O–O coupling. The resulting polymeric product of
magnolol is a non-conducting film which will retard the mass and electron transfer of
magnolol to the electrode surface.
Fig. S 1 1H-NMR and
13C-NMR
of 3-[1-butoxycarbnyl amino-propyl]-1-[3-(N
-pyrrole)propyl]imidazolium tetrafluoroborate ionic liquid
The inserted pictures are the assignments of 1H NMR and 13C NMR with the chemical
structure.
Fig. S 2 FTIR spectroscopy of 3-[1-butoxycarbnyl amino-propyl] -1-[3-(N
-pyrrole)propyl]imidazolium tetrafluoroborate ionic liquid
Fig.
S3
Mass
spectrum
of
3-[1-butoxycarbnyl
amino-propyl]-1-[3-(N
-pyrrole)propyl]imidazolium cation.
The m/z result indicates that the detected molecular weight of 3-[1-butoxycarbnyl
amino-propyl]-1-[3-(N -pyrrole)propyl]imidazolium cation is 333.23186 which is
consist with the theoretic molecular weight of this compound.
Fig. S5 (a) Cyclic voltammograms of magnolol at the polymerized ionic liquid
film electrode with different scan rate; (b) Relationship between the
peak current and scan rate; (c) Relationship between peak potential and
natural logarithm of scan rate.
Fig. S 6 Differential pulse voltammograms of magnolol at the polymerized ionic
liquid film electrode (e) and in the presence of ascorbic acid (a), catechol
(b), dopamine (c) and uric acid (d).
Fig. S 7 Differential pulse voltammogram for honokiol (a) and magnolol (b) at
the
polymerized
ionic
liquid
film
electrode.
Fig. S 8 Differential pulse voltammograms of magnolol at different concentration.
Fig. S 9 Calibration curve for magnolol determination at the polymerized ionic
liquid film electrode.
Fig. S 10 Differential pulse voltammograms of Magnolia officinalis sample (a)
and addition of 0.2 µmol L-1 magnolol (b).