Supporting material
Polyethylene glycol/graphene oxide-coated solid-phase microextraction fiber for analysis of phenols and phthalate esters coupled with gas chromatography
Xiudan Hou
1,2
, Hui Yu
1,2
, Yong Guo
1
, Xiaojing Liang
1
, Shuai Wang
1
,
Licheng Wang
1,
*, Xia Liu
1,
**
1
Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000, China
2
University of the Chinese Academy of Sciences, Chinese Academy of Sciences,
Beijing 100049, China
3.1 Preparation of PEG/GO-coated fiber
As can be seen in Fig. S-1 , the GC peak areas of analytes increased as the molecular weight of PEG increased. Thus 20,000 g/mol of PEG was used to prepare the fiber coating with GO. This was related to the stability of PEG. Due to the soft chains, the PEG of lower molecular weight was prone to disintegrate at high temperature. Besides, for the preparation of PEG/GO-coated fiber, the amount ratio of
PEG to GO was also investigated, which affected the extraction efficiency of coating.
100, 150, 200, 250 mg of PEG were dissolved in 1mL of ultrapure water, respectively.
The above prepared PEG solutions were added to 1 mL of 0.1 % GO solution. The

result was demonstrated in Fig. S-2, which showed that 200 mg of PEG was the optimal amount to extract model compounds.
3.2 Characterization of the fiber
IR spectrum was used to determine the successful addition of PEG molecules to the GO solution. Before the characterization, the GO and PEG/GO powders were cut down from the prepared fibers .As can be seen in Fig. S-3, the PEG/GO sample exhibited the obviously change of signal peaks compared with GO. The characteristic signals of GO were as following: the O-H stretching vibration of the -OH groups appeared at 3423 cm
-1
; the stretching vibration of C=O from the -COOH groups at
1654 cm
-1
; C-O vibration at 1136 cm
-1
. For comparison of GO powder, the PEG/GO displayed the peaks of 2881 cm -1 and 1530 cm -1 , which can be ascribed to the stretching vibration and scissor bending vibration of CH
2
from PEG chains, respectively. Based on the above information, the appearance of CH
2 various characteristic peaks fully demonstrated that the PEG molecules were immobilized onto the fiber surface with GO, successfully.
Elemental analysis (Table S-1) was also used to determine the hydrogen content.
The result exhibited that the 7.17 % hydrogen of PEG/GO was obviously higher than the 1.89 % of GO, which also verified the synthesis of composite coating.
Morphology of the prepared fiber was investigated by SEM.
Captions

Fig. S-1 Effect of the PEG molecular weight on peak areas of analytes.
Fig. S-2 Effect of the polyethylene glycol amount on peak areas of analytes.
Fig. S-3 Fourier transform infrared spectrometer of the polyethylene glycol/graphene oxide (a) and graphene oxide (b) fiber coatings.
Fig. S-4 Comparison of GC peak areas of analytes before and after dipping the tip of the PEG/GO-coated fiber into three different solutions for 48 h.
Table S-1 Elemental analysis of GO and PEG/GO coating.
Table S-2 A comparison in solid-phase microextraction performance with other graphene-based fibers.
Fig. S-1

Fig. S-2
Fig. S-3

Fig. S-4
Table S-1
C
H
GO (%) PEG/GO (%)
39.9
1.89
51.72
7.17

No. SPME coating
1
2
3
4
5
6
7
G substrateless G
G
Analytes
PAHs organochlorine pesticides pyrethroids
Table S-2
LODs
(ng/L)
1.52-2.72
0.83-11.5
3.6-69.4
G nanosheets
G
G
PEG/GO organochlorine pesticides polybrominated diphenyl ethers triazine herbicides phenols and PAEs
0.16-0.93
0.2-5.3
50-200
3-25
Linear range
(ng/L)
5-500
2-1000
4-1000
8-1000
20-10000
50-100000
100-100000
1-500
2-1000
5-1000
10-1000
500-200000
10-200000
50-200000
100-200000
Ref.
[10]
[37]
[21]
[38]
[39]
[40]
This study
References
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