Supporting Information
Determination of preservatives in soft drinks by
capillary electrophoresis with ionic liquids as
electrolyte additives
Bingbing Sun a, b, Li Qi a *, Minglin Wang b
a Beijing
National Laboratory for Molecular Sciences, Key Lab of Analytical
Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy
of Sciences, Beijing 100190, P. R. China
b
College of Food Sciences and Engineering, Shandong Agricultural
University, Tai’an, Shandong 271018, P. R. China
* Corresponding author:
E-mail:
qili@iccas.ac.cn
1
Table S1 Effect of the IL concentrations on separation of the analytes*
Concentration
of IL (mM)
**Rs1
**Rs2
**Rs3
**Rs4
**Rs5
**Rs6
**Rs7
10
2.35
2.99
4.34
7.72
0
6.85
24.52
15
2.44
3.12
4.59
9.23
0.82
7.38
28.38
20
2.39
3.03
4.35
8.34
1.24
6.79
28.48
25
2.56
3.31
4.79
9.15
1.76
6.95
31.37
30
2.55
3.20
4.44
8.38
1.92
6.25
31.25
* Buffer condition: pH 10.0 in various IL concentrations. Other separation conditions were the same as
that in Fig. 2.
** Rs1: resolution between butyl p-hydroxybenzoate and propyl p-hydroxybenzoate;
Rs2: resolution between propyl p-hydroxybenzoate and ethyl p-hydroxybenzoate;
Rs3: resolution between ethyl p-hydroxybenzoate and methyl p-hydroxybenzoate;
Rs4: resolution between methyl p-hydroxybenzoate and m-amino benzoic acid;
Rs5: resolution between m-amino benzoic acid and sorbic acid;
Rs6: resolution between sorbic acid and benzoic acid;
Rs7: resolution between benzoic acid and p-hydroxybenzoate.
2
Fig.S1 Effect of pH on separation of the analytes. Other separation conditions
were the same as that in Fig. 2.
3
Table S2 The effect of concentration of borax *
Concentration
of borax (mM)
Rs1
Rs2
Rs3
Rs4
Rs5
Rs6
Rs7
1
1.36
1.60
2.26
10.17
0.71
3.80
11.64
5
2.14
2.71
3.82
9.23
1.46
6.17
17.85
10
2.25
2.88
4.06
8.27
1.49
6.22
23.25
15
2.56
3.31
4.79
9.15
1.76
6.95
31.37
* Other separation conditions were the same as that in Fig. 2.
4
Table S3 Quantification of preservatives*
Analytes
Calibration
equation
Correlation
coefficient
Range
(µM)
LOD
(µM)
Methyl p-hydroxybenzoate
y=4.54×102x -9.70×102
0.999
8.22-1.64×103
4.11
Ethyl p-hydroxybenzoate
y=3.83×103x +3.51×103
0.999
7.52-1.50×103
3.76
Propyl p-hydroxybenzoate
y=3.86×102x -1.35×103
0.999
6.94-1.39×103
3.47
Butyl p-hydroxybenzoate
y=3.70×102x +4.55×102
0.998
6.44-1.29×103
3.22
p-Hydroxybenzoic acid
y=2.36×103x -8.15×103
0.998
4.52-1.81×103
2.26
Sorbic acid
y=3.76×103x +2.26×104
0.999
5.57-2.23×103
2.79
Benzoic acid
y=1.42×102x +1.95×103
0.999
10.24-2.05×103
5.12
m-Amino benzoic acid
y=2.11×103x +1.93×104
0.999
8.21-1.64×103
4.10
* The separation conditions were the same as that in Fig. 2.
5
Table S4 The extraction recoveries of preservatives in soft drinks*
Lemon
Analytes
Methyl p-hydroxybenzoate
Ethyl p-hydroxybenzoate
Propyl p-hydroxybenzoate
Butyl p-hydroxybenzoate
p-Hydroxybenzoic acid
Sorbic acid
Benzoic acid
juice
Grape
juice
Vitamine
beverage
Haw
juice
Added
Recovery
RSD
Recovery
RSD
Recovery
RSD
Recovery
RSD
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
80
105.7
3.1
108.3
4.9
97.2
4.1
105.7
2.4
500
104.3
2.0
109.4
4.5
99.7
3.6
101.7
3.8
80
109.5
1.3
112.9
2.6
100.1
4.1
109.1
3.1
500
113.6
2.5
114.3
1.3
112.9
2.6
111.3
1.7
80
114.0
2.1
114.5
1.4
111.2
4.0
107.1
3.0
500
112.3
1.8
112.2
4.1
111.1
1.3
110.5
1.6
80
104.9
3.6
108.3
3.1
103.8
1.1
107.6
1.6
500
106.2
3.5
106.1
1.5
103.9
1.0
108.6
2.8
80
111.9
1.9
103.9
3.6
105.6
2.6
106.9
3.8
500
110.2
2.3
103.0
1.4
100.8
3.3
104. 6
1.1
80
101.9
4.2
102.9
3.0
103.1
1.7
111.5
1.5
500
101.7
1.5
116.7
2.4
117.3
4.2
100.1
3.7
80
104.1
4.3
108.7
1.8
102.6
3.9
109.7
4.3
500
109.9
2.3
97.2
1.9
117.5
1.9
115.4
3.3
80
79.4
1.9
83.4
4.1
86.3
3.6
91.4
3.9
500
88.9
1.0
89.6
2.1
86.2
1.7
94.1
1.1
(uM)
m-Amino benzoic acid
* The separation conditions were the same as that in Fig. 2.
6