Development of a sequential dispersive liquid-liquid
microextraction method for the determination of
aryloxyphenoxy-propionate herbicides in water samples
Songqing Li, Peng Gao, Jiaheng Zhang, Yubo Li, Bing Peng, Haixiang Gao, Wenfeng Zhou*
Department of Applied Chemistry, China Agricultural University, Beijing 100193, China
Running title: Development of a sequential DLLME method
Correspondence: Associate professor Wenfeng Zhou, Department of Applied Chemistry, College of
Science, China Agricultural University, Beijing 100193, P. R. China
E-mail address: [email protected]
Fax: +86 1062733830;
Tel.: +86 1062731991.
1
Table S1. Independent variables, abbreviations and levels used in the central composite design matrix
Variables
Abbreviations
Amount of [C8MIM]Cl (mg)
Volume of chlorobenzene (μL)
Ultrasonication time (min)
pH
Concentration of NaCl (%)
IL
CB
UT
pH
NaCl
Levels
Star(−α)a
5
10
0
5
2
Low(−1)
10
20
1
6
4
High(+1)
20
40
3
8
8
Star(+α)
25
50
4
9
10
In the half-fraction CCD, α = 2 is used to design the experiment points.
a
2
Table S2. Half-fraction central composite design matrix of five variables (in coded units) and responses.
Run. No
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Variables
IL
CB
+1
-1
-α
0
-1
-1
-1
-1
0
0
+α
0
0
-α
+1
+1
0
0
0
0
-1
+1
0
+α
0
0
0
0
-1
-1
+1
-1
-1
-1
-1
+1
+1
+1
-1
+1
+1
+1
0
0
0
0
+1
-1
+1
+1
+1
-1
-1
+1
0
0
UT
+1
0
-1
-1
0
0
0
+1
0
0
+1
0
0
0
+1
-1
+1
+1
-1
-1
-1
0
0
+1
+1
-1
-1
+α
pH
+1
0
-1
+1
0
0
0
-1
-α
0
+1
0
0
+α
+1
-1
-1
-1
-1
+1
+1
0
0
-1
+1
+1
-1
0
NaCl
-1
0
+1
-1
+α
0
0
-1
0
0
-1
0
0
0
+1
-1
-1
+1
+1
+1
-1
0
-α
+1
+1
+1
-1
0
Response
ER1%
68.45
79.74
74.89
76.18
65.47
78.61
68.05
76.29
67.58
76.10
80.78
77.08
79.22
64.47
70.67
80.81
80.73
77.65
72.30
68.06
71.12
73.79
79.39
64.18
79.38
60.60
80.73
75.54
EF1
144.1
199.4
221.9
217.7
130.9
114.3
247.5
105.2
128.7
145.0
134.6
99.5
150.9
122.8
217.5
170.1
230.6
135.0
103.3
118.4
98.1
140.6
147.7
142.6
113.4
134.7
134.5
143.9
ER2%
81.53
95.65
90.13
86.22
80.14
91.34
75.45
101.66
85.06
92.39
95.81
96.07
94.47
78.89
82.78
86.21
95.14
100.36
91.07
83.76
90.93
91.20
89.52
81.12
90.52
73.61
99.45
92.01
EF2
171.6
239.1
267.1
246.3
160.3
132.9
274.4
140.2
162.0
176.0
159.7
124.0
179.9
150.3
254.7
181.5
271.8
174.5
130.1
145.7
125.4
173.7
166.6
180.3
129.3
163.6
165.7
175.3
ER3%
71.18
80.54
73.05
79.40
71.29
83.86
69.45
86.48
80.59
81.54
85.54
86.53
83.32
67.75
73.05
82.05
81.76
82.26
80.50
76.00
79.23
80.31
84.95
67.44
80.50
66.27
86.21
78.81
EF3
149.9
201.4
216.4
226.9
142.6
122.0
252.5
119.3
153.5
155.3
142.6
111.7
158.7
129.0
224.8
172.7
233.6
143.1
115.0
132.2
109.3
153.0
158.0
149.9
115.0
147.3
143.7
150.1
ER4%
85.27
90.97
96.29
75.88
86.64
87.70
75.81
106.55
72.94
98.66
76.54
96.93
101.02
69.09
64.73
80.01
98.99
97.60
86.86
107.54
106.07
96.86
92.42
74.46
88.94
84.53
89.01
92.09
EF4
179.5
227.4
296.3
216.8
173.3
127.6
275.7
147.0
138.9
187.9
127.6
125.1
192.4
131.6
199.2
168.4
282.8
169.7
124.1
187.0
146.3
184.5
171.9
165.5
127.1
187.8
148.3
175.4
3
Table S3. Estimated regression coefficients for the recovery and enrichment factor of haloxyfop-R-methyl (ER1% and EF1)
Term
ER1%
Coef.
EF1
Constant
IL
CB
UT
pH
NaCl
IL2
75.788
−1.618
1.994
0.621
−1.606
−3.134
1.065
Std. Err.
Coef.
1.6386
0.6016
0.6016
0.7165
0.6016
0.6016
0.6084
t-value
p-value
CB2
−0.586
0.6084
−0.964
0.367
7.667
1.305
5.874
0.001
UT2
0.0652
0.7501
0.087
0.933
0.109
1.609
0.068
0.948
pH2
−2.222
0.6084
−3.652
0.008
−4.259
1.305
−3.263
0.014
NaCl2
−0.621
0.6084
−1.021
0.341
−0.870
1.305
−0.666
0.527
IL × CB
IL × UT
IL × pH
IL × NaCl
CB × UT
CB × pH
CB × NaCl
UT × pH
UT × NaCl
pH × NaCl
1.269
−0.407
0.266
0.433
1.898
1.067
1.518
2.074
1.164
0.733
0.7368
0.7368
0.7368
0.7368
0.7368
0.7368
0.7368
0.7368
0.7368
0.7368
1.722
−0.552
0.362
0.587
2.576
1.447
2.061
2.815
1.579
0.995
0.129
0.598
0.728
0.575
0.037
0.191
0.078
0.026
0.158
0.353
12.098
−1.635
0.188
0.071
2.723
2.361
2.718
3.569
2.257
1.695
1.581
1.581
1.581
1.581
1.581
1.581
1.581
1.581
1.581
1.581
7.654
−1.034
0.119
0.045
1.723
1.494
1.719
2.258
1.428
1.072
0.000
0.335
0.909
0.965
0.129
0.179
0.129
0.059
0.196
0.319
46.252
−2.690
3.314
0.866
−2.669
−5.209
1.751
0.000
0.031
0.013
0.415
0.032
0.001
0.123
Coef.
144.400
−23.699
−34.692
1.128
−3.201
−3.411
3.512
Std. Err.
Coef.
3.515
1.291
1.291
1.537
1.291
1.291
1.305
t-value
p-value
41.078
−18.362
−26.879
0.734
−2.480
−2.643
2.691
0.000
0.000
0.000
0.487
0.042
0.033
0.031
4
Table S4. The R-squared and adjusted R-squared statistics and standard deviations of the residuals used in the regression model.
Response
R2
R2 (adj)
S
ER1%
EF1
93.71
99.43
75.74
97.79
2.947
6.323
ER2%
EF2
93.57
99.34
75.20
97.46
3.669
7.346
ER3%
EF3
95.41
99.40
82.30
97.67
2.611
6.103
ER4%
EF4
96.36
98.82
85.97
95.47
4.346
10.016
5
Table S5. Analysis of variance (ANOVA) for the recovery and enrichment factor of each herbicide in coded units
ER1%
EF1
Source
D.f.a
SSb
Seq
Regression
Linear
20
5
905.95
470.04
905.95
462.34
Square
Interaction
5
10
191.52
244.38
Residual Error
Lack-of-Fit
Pure Error
7
5
2
60.81
45.93
14.88
Total
27
966.75
Adj
SSb
Adj
MSc
F
P
45.297
92.468
5.21
10.64
0.016
0.004
191.52
244.38
38.304
24.438
4.41
2.81
60.81
45.93
14.88
8.687
9.185
7.441
1.23
Seq SS
Adj SS
20
5
48645.9
42896.5
48645.9
42909.9
0.039
0.091
5
10
2706.9
3042.5
0.504
7
5
2
279.8
225.9
54.0
27
48925.8
ER2%
D.f.
Seq SS
Adj SS
Regression
20
1371.42
1371.42
68.571
5.09
0.017
Linear
Square
Interaction
5
5
10
1104.12
184.63
82.67
1075.89
184.63
82.67
215.179
36.925
8.267
15.99
2.74
0.61
0.001
0.110
0.766
Residual Error
7
94.22
94.22
13.460
Lack-of-Fit
Pure Error
Total
5
2
27
88.74
5.48
1465.63
88.74
5.48
17.748
2.739
Adj MS
F
6.48
P
0.139
ER3%
D.f.
Regression
Linear
Square
20
5
5
Adj MS
F
P
2432.3
8582.0
60.84
214.67
0.000
0.000
2706.9
3042.5
541.4
304.3
13.54
7.61
0.002
0.007
279.8
225.9
54.0
40.0
45.2
27.0
1.67
0.415
EF2
Source
Source
D.f.
D.f.
Seq SS
Adj SS
Adj MS
F
P
20
57007.0
57007.0
2850.4
52.81
0.000
5
5
10
51318.5
2468.3
3220.3
51324.4
2468.3
3220.3
10264.9
493.7
322.0
190.20
9.15
5.97
0.000
0.006
0.013
7
377.8
377.8
54.0
5
2
27
357.9
19.9
57384.8
357.9
19.9
71.6
9.9
7.20
0.126
EF3
Seq SS
991.82
793.71
95.32
Adj SS
991.82
792.86
95.32
Adj MS
F
P
49.591
158.571
19.063
7.28
23.27
2.80
0.006
0.000
0.106
D.f.
20
5
5
Seq SS
Adj SS
42893.1
38544.9
1955.9
42893.1
38553.3
1955.9
Adj MS
2144.7
7710.7
391.2
F
P
57.57
207.00
10.50
0.000
0.000
0.004
6
Interaction
10
102.80
102.80
10.280
Residual Error
Lack-of-Fit
7
5
47.71
43.15
47.71
43.15
6.816
8.629
Pure Error
2
4.56
4.56
2.282
Total
27
1039.53
1.51
3.78
0.301
10
2392.4
2392.4
239.2
6.42
0.011
0.222
7
5
260.8
244.2
260.8
244.2
37.3
48.8
5.90
0.151
2
16.6
16.6
8.3
27
43153.9
ER4%
EF4
Source
D.f.
Seq SS
Adj SS
Adj MS
F
Regression
20
3503.61
3503.61
175.180
9.27
0.003
Linear
Square
5
5
995.53
894.92
1079.79
894.92
215.959
178.984
11.43
9.47
Interaction
10
1613.16
1613.16
161.316
8.54
Residual Error
Lack-of-Fit
7
5
132.24
123.53
132.24
123.53
18.891
24.706
Pure Error
2
8.70
8.70
4.352
Total
27
3635.84
a
5.68
P
D.f.
Seq SS
Adj SS
Adj MS
F
P
20
59042.4
59042.4
2952.1
29.43
0.000
0.003
0.005
5
5
43450.6
4823.6
43676.6
4823.6
8735.3
964.7
87.08
9.62
0.000
0.005
0.005
10
10768.1
10768.1
1076.8
10.73
0.002
0.157
7
5
702.2
670.6
702.2
670.6
100.3
134.1
8.50
0.109
2
31.6
31.6
15.8
27
59744.6
D.f.: Degrees of freedom
b SS:
Sum of square
c MS:
Mean square
7
Table S6. Comparison of EFs in the sequential DLLME and each individual DLLME for the analysis of the studied ArPPE herbicides
at 50 μg L−1 spiked level
Pesticide
Haloxyfop-R-methyl
Cyhalofop-butyl
Fenoxaprop-p-ethyl
Fluazifop-p-butyl
Sequential
DLLME
171
192
173
179
In situ
IL-DLLME
168
153
153
121
Conventional
DLLME
170
138
146
115
Ultrasound-assisted
DLLME
175
157
157
148
8
Fig. S1. Formation of octyl-3-methylimidazoliumbis[(trifluoromethane)sulfonyl]imide using an in situ halide exchange reaction
9
Fig. S2. Response surface plots for the extraction recovery of haloxyfop-R-methyl (ER1%) as a function of certain significant factors:
(i) CB volume and IL amount and (ii) concentration of NaCl and pH
10
Fig. S3. Response surface plots for the enrichment factor of haloxyfop-R-methyl (EF) as a function of certain significant factors: (i) CB
volume and IL amount and (ii) concentration of NaCl and pH
11