- Email: [email protected]
Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography
G Model
CCLET-3417; No. of Pages 3 Chinese Chemical Letters xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters journal homepage: www.elsevier.com/locate/cclet
Original article
Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography Yan-Fen Zhang, Mei-Ling Qi *, Ruo-Nong Fu Department of Analytical Chemistry, School of Chemistry, Beijing Institute of Technology, Beijing 100081, China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 April 2015 Received in revised form 6 May 2015 Accepted 26 May 2015 Available online xxx
Polydopamine (PDA) coating, a nature-inspired polymer, has attracted great attention in many areas due to its high adhesion strength and stability on almost all types of substrate surfaces. This work presents the first example of using PDA coating as a column pretreatment method in capillary gas chromatography (GC) and its employment in the column fabrication of cucurbit[7]uril (CB7) stationary phase. The fabricated PDA-CB7 column exhibited weakly polar nature and had advantages over CB7 column without PDA for the separations of some critical analytes in GC. This work demonstrates the advantage and potential of using PDA as a facile column pretreatment method in capillary GC column fabrication. ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Keywords: Polydopamine-based coating Cucurbit[7]uril Separation performance Capillary gas chromatography
1. Introduction Polydopamine (PDA) is a nature-inspired polymer and can be in situ formed on almost any type of substrate surfaces by using a dopamine solution in Tris buffer at pH 8.5 via polymerization [1–3]. PDA coating has attracted growing attention over the past decade due to its fascinating features such as strikingly high adhesion strength on substrate surface and its ability to further adhere or bind other materials of interest onto its surface [4]. Recently, PDA coating has also found its use in the surface pretreatment of a fused-silica capillary column in capillary electrophoresis (CE) [5,6]. It may also have potential in capillary gas chromatography (GC). However, as a result of a recent survey, no related publications are available up to now. PDA coating basically consists of dihydroxyindole and indoledione units [3] and may exhibit a stronger binding ability to a GC stationary phase with H-bonding and dipole–dipole nature. From this perspective, cucurbit[n]urils (CBs) [7] can be an ideal choice for the integration with PDA coating. This work reports the column fabrication of CB7 stationary phase on PDA precoating (denoted as PDA-CB7 column) and its GC separation performance. CB7 is of symmetric and rigid structure with a hydrophobic cavity and two identical polar portals laced with multiple carbonyl groups and shows good separation performance as GC stationary phase [8]. Meanwhile, one CB7 capillary column
* Corresponding author. E-mail address: [email protected] (M.-L. Qi).
prepared with a conventional coating method without PDA coating (denoted as CB7 column) and one commercial column (DB-35MS) were also used for comparison. Interestingly, we found that integration of PDA coating with CB stationary phase did make a difference from the conventional coating method and the presence of PDA coating also partially contributed to GC separations.
2. Experimental 2.1. Chemicals and instruments All the analytes were of analytical grade. CB7 was synthesized following the method we previously reported [8]. Untreated fusedsilica capillary tubing (0.25 mm i.d.) was purchased from Yongnian Ruifeng Chromatogram Apparatus Company (Hebei, China). All gas chromatographic separations were performed on an Agilent GC 7890A gas chromatograph with a flame ionization detector (FID) under the following GC conditions: nitrogen of high purity (99.999%) as carrier gas at a flow rate of 1 mL/min, injection port at 250 8C and FID at 300 8C. Temperature programs for the separations of different samples are individually provided in their figure captions. 2.2. Capillary column fabrication PDA-CB7 column was fabricated as follows. A capillary column (10 m 0.25 mm, i.d.) was filled with a dopamine solution (1.2 mg/mL dopamine in 10 mmol/L Tris–HCl buffer, pH 8.5) and
http://dx.doi.org/10.1016/j.cclet.2015.05.054 1001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054
G Model
CCLET-3417; No. of Pages 3 Y.-F. Zhang et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
2
stayed for 24 h at room temperature. After this, the solution in the capillary was flushed out and washed with water for 5 min and dried under nitrogen. The obtained PDA coating showed orderly crumpled morphology (Fig. S1 in Supporting information). Then, the column with PDA was further statically coated with the suspension of CB7 stationary phase in dichloromethane (0.25%, w/v) at room temperature. Briefly, after the column was filled with the suspension, one end of the capillary was sealed and the other was connected to a vacuum system to gradually remove the solvent. The coated capillary columns were then conditioned from 40 to 180 8C at the rate of 1 8C/min and held at the high-end temperature for 7 h under a constant flow of nitrogen at 1 mL/min. CB7 column without PDA was prepared by the method described in the reference [8]. 3. Results and discussion 3.1. McReynolds constants and column efficiency Column efficiency of PDA-CB7 column was determined by isothermal determination of n-dodecane at 120 8C and evaluated by the theoretical plate number per meter. As a result, PDA-CB7 column exhibited a column efficiency of 2823 plates/m. McReynolds constants were determined at 120 8C by using five probe compounds, namely benzene (X0 ), 1-butanol (Y0 ), 2-pentanone (Z0 ), 1-nitropropane (U0 ) and pyridine (S0 ). Table 1 lists the obtained McReynolds constants for PDA-CB7 column as well as CB7 column. As shown, PDA-CB7 column showed average polarity of 122, slightly higher than that of CB7 column, suggesting their weakly polar nature. Relatively, PDA-CB7 column had higher Y0 , U0 and S0 values than CB7 column, suggesting its slightly stronger H-bonding and dipole–dipole interactions with H-bonding analytes than CB7 column possibly due to the presence of PDA coating. 3.2. Separation performance Separation performance of PDA-CB7 column was investigated by separations of analytes of different variety, including n-alkanes, halogenated benzenes and the Grob test mixture. Fig. 1 shows the separations of n-alkanes (a) and halogenated benzenes (b) on PDACB7 column, showing its good separation performance for common analytes. To examine its performance for critical analytes, the Grob mixture, the most challenging mixture in GC, was separated, while a CB7 column without PDA and a commercial DB-35MS column were used for comparison (Fig. 2).
250
(a) 1
200
Columns
X0
Y0
Z0
U0
S0
Sum
Average
PDA-CB7 CB7 DB-35MS
33 11 102
187 146 142
97 78 145
169 124 219
122 82 178
608 441 786
122 88 157
X0 : benzene, Y0 : 1-butanol, Z0 : 2-pentanone, U0 : 1-nitropropane, S0 : pyridine.
As evidenced in Fig. 2, PDA-CB7 and CB7 columns shared the same elution order for the analytes but differed from the commercial column for some of them. Noticeably, PDA-CB7 column exhibited good resolution for most of them, especially for the peak pairs of n-undecane/1-nonanal/1-octanol (peaks 3/4/ 5, a3/4 = 1.03, a4/5 = 1.06) and dicyclohexylamine/methyl undecanoate (peaks 10/11, a9/10 = 1.01), which completely coeluted on CB7 column. This finding suggested the partial contribution of PDA coating to the separation. The analytes of n-undecane, 1-nonanal and 1-octanol share a quite close boiling point but have different polarity. PDA-CB7 column exhibited higher selectivity for these analytes probably due to its additional interactions with these analytes via H-bonding and dipole–dipole interactions. These additional interactions may be minor but did make a difference when working together with CB7 stationary phase in achieving improved separations of the indicated analytes. In contrast to the commercial column, PDA-CB7 column switched the elution order of two peak pairs, namely 1-nonanal/1-octanol (peaks 4/5) and 2,6dimethylaniline/2-ethylhexanoic acid (peaks 7/8). The later elution of 1-octanol and 2-ethylhexanoic acid on PDA-CB7 column indicated their stronger H-bonding and dipole–dipole interactions with PDA-CB7 coating, which may also lead to their tailing peaks. Additionally, PDA-CB7 column showed wider peaks due to its lower column efficiency which might be attributed to the adsorption nature of PDA-CB7 column for the separations. The above findings demonstrate that PDA precoating is feasible in GC column fabrication and also helpful for improving the resolving ability of the as-fabricated column for critical analytes such as aldehydes and amines. 3.3. Separation repeatability and thermal stability Furthermore, separation repeatability of PDA-CB7 column was also examined by separation of a mixture of 11 analytes and evaluated by relative standard deviations (RSD %) in retention times of the analytes. The obtained RSD values are listed in Table S1, showing 0.01–0.05% for intra-day (n = 6), 0.06–0.69% for inter-day
600
8
(b)
3
2
3
6 4
7
1
5
400 2
150 pA
pA
Table 1 McReynolds constants of PDA-CB7, CB7 and DB-35MS capillary columns.
4
5
200
100
50 0
2
4
6 Time (min)
8
10
0 0
2
4
6
Time (min)
Fig. 1. Separations of n-alkanes (a) and halogenated benzenes (b) on PDA-CB7 column. Peaks for (a): (1) nonane, (2) decane, (3) undecane, (4) dodecane,. (5) tridecane, (6) tetradecane, (7) pentadecane, (8) hexadecane; for (b): (1) chlorobenzene, (2) bromobenzene, (3) 1,4-dichlorobenzene, (4) 1,2-dichlorobenzene, (5)1,2,4-trichlorobenzene. Temperature programs: (a) 40 8C (1 min) to 130 8C at 10 8C/min and (b) 40 8C (1 min) to 90 8C at 10 8C/min.
Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054
G Model
CCLET-3417; No. of Pages 3 Y.-F. Zhang et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
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9
10
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5
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400
11
200
pA
500
1
4
1
100
6
9
12
8
300
1
200 100
50 05101520
024681012
Time (min)
7
400
7
100 8
9 10 5
10+11
4+56
150
DB-35MS11 12
3
500
3
300 6
2
600
12
pA
3
200
700
250
2
600
pA
CB7
PDA-CB7
3
48
02468101214
Time (min)
Time (min)
Fig. 2. Separations of the Grob mixture on PDA-CB7, CB7 and DB-35MS capillary columns. Peaks: (1) 2,3-butanediol, (2) n-decane, (3) n-undecane, (4) nonanal, (5) 1-octanol, (6) 2,6-dimethylphenol, (7) 2,6-dimethylaniline, (8) 2-ethylhexanoic acid, (9) methyl decanoate, (10) dicyclohexylamine, (11) methyl undecanoate, (12) methyl dodecanoate. Temperature programs: 40 8C (1 min) to 160 8C at 10 8C/min for PDA-CB7 and DB-35 columns and 40 8C (1 min) to 160 8C at 5 8C/min for CB7 column.
(n = 6) and 2.7–6.4% for between-column (n = 3), respectively. These results demonstrated the good repeatability of PDA-CB7 column for GC separations. In addition, the column also exhibited good thermal stability up to 270 8C. 4. Conclusion This work introduced PDA coating into GC column fabrication and presented the first example of employing PDA coating as an efficient GC column pretreatment method. This work demonstrates that PDA coating not only served for the pretreatment but also made a partial contribution to GC separations. Integration of PDA coating with CB7 achieved enhanced resolving ability in contrast to neat CB7 column, suggesting the possible synergic interactions PDA coating with CB7 stationary phase. This work shows that PDA coating for GC column pretreatment is facile and efficient and has advantages over the conventional method in separation performance. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 21075010) and the 111 Project B07012 in China.
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.cclet.2015.05.054. References [1] M.J. Sever, J.T. Weisser, J. Monahan, S. Srinivasan, J.J. Wilker, Metal-mediated crosslinking in the generation of a marine-mussel adhesive, Angew. Chem. Int. Ed. 43 (2004) 447–450. [2] H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Mussel-inspired surface chemistry for multifunctional coatings, Science 318 (2007) 426–430. [3] J. Liebscher, R. Mro´wczyn´ski, H.A. Scheidt, et al., Structure of polydopamine: a never-ending story? Langmuir 29 (2013) 10539–10548. [4] S.M. Kang, N.S. Hwang, J. Yeom, S.Y. Park, P.B. Messersmith, I.S. Choi, R. Langer, D.G. Anderson, H. Lee, One-step multipurpose surface functionalization by adhesive catecholamine, Adv. Funct. Mater. 22 (2012) 2949–2955. [5] X.B. Yin, D.Y. Liu, Polydopamine-based permanent coating capillary electrochromatography for auxin determination, J. Chromatogr. A 1212 (2008) 130–136. [6] R.J. Zeng, Z.F. Luo, D. Zhou, F.H. Cao, Y.M. Wang, A novel PEG coating immobilized onto capillary through polydopamine coating for separation of proteins in CE, Electrophoresis 31 (2010) 3334–3341. [7] J. Lagona, P. Mukhopadhyay, S. Chakrabarti, L. Isaacs, The cucurbit[n]uril family, Angew. Chem. Int. Ed. 44 (2005) 4844–4870. [8] P. Zhang, S.J. Qin, M.L. Qi, R.N. Fu, Cucurbit[n]urils as a new class of stationary phases for gas chromatographic separations, J. Chromatogr. A 1334 (2014) 139–148.
Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054
CCLET-3417; No. of Pages 3 Chinese Chemical Letters xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters journal homepage: www.elsevier.com/locate/cclet
Original article
Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography Yan-Fen Zhang, Mei-Ling Qi *, Ruo-Nong Fu Department of Analytical Chemistry, School of Chemistry, Beijing Institute of Technology, Beijing 100081, China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 April 2015 Received in revised form 6 May 2015 Accepted 26 May 2015 Available online xxx
Polydopamine (PDA) coating, a nature-inspired polymer, has attracted great attention in many areas due to its high adhesion strength and stability on almost all types of substrate surfaces. This work presents the first example of using PDA coating as a column pretreatment method in capillary gas chromatography (GC) and its employment in the column fabrication of cucurbit[7]uril (CB7) stationary phase. The fabricated PDA-CB7 column exhibited weakly polar nature and had advantages over CB7 column without PDA for the separations of some critical analytes in GC. This work demonstrates the advantage and potential of using PDA as a facile column pretreatment method in capillary GC column fabrication. ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Keywords: Polydopamine-based coating Cucurbit[7]uril Separation performance Capillary gas chromatography
1. Introduction Polydopamine (PDA) is a nature-inspired polymer and can be in situ formed on almost any type of substrate surfaces by using a dopamine solution in Tris buffer at pH 8.5 via polymerization [1–3]. PDA coating has attracted growing attention over the past decade due to its fascinating features such as strikingly high adhesion strength on substrate surface and its ability to further adhere or bind other materials of interest onto its surface [4]. Recently, PDA coating has also found its use in the surface pretreatment of a fused-silica capillary column in capillary electrophoresis (CE) [5,6]. It may also have potential in capillary gas chromatography (GC). However, as a result of a recent survey, no related publications are available up to now. PDA coating basically consists of dihydroxyindole and indoledione units [3] and may exhibit a stronger binding ability to a GC stationary phase with H-bonding and dipole–dipole nature. From this perspective, cucurbit[n]urils (CBs) [7] can be an ideal choice for the integration with PDA coating. This work reports the column fabrication of CB7 stationary phase on PDA precoating (denoted as PDA-CB7 column) and its GC separation performance. CB7 is of symmetric and rigid structure with a hydrophobic cavity and two identical polar portals laced with multiple carbonyl groups and shows good separation performance as GC stationary phase [8]. Meanwhile, one CB7 capillary column
* Corresponding author. E-mail address: [email protected] (M.-L. Qi).
prepared with a conventional coating method without PDA coating (denoted as CB7 column) and one commercial column (DB-35MS) were also used for comparison. Interestingly, we found that integration of PDA coating with CB stationary phase did make a difference from the conventional coating method and the presence of PDA coating also partially contributed to GC separations.
2. Experimental 2.1. Chemicals and instruments All the analytes were of analytical grade. CB7 was synthesized following the method we previously reported [8]. Untreated fusedsilica capillary tubing (0.25 mm i.d.) was purchased from Yongnian Ruifeng Chromatogram Apparatus Company (Hebei, China). All gas chromatographic separations were performed on an Agilent GC 7890A gas chromatograph with a flame ionization detector (FID) under the following GC conditions: nitrogen of high purity (99.999%) as carrier gas at a flow rate of 1 mL/min, injection port at 250 8C and FID at 300 8C. Temperature programs for the separations of different samples are individually provided in their figure captions. 2.2. Capillary column fabrication PDA-CB7 column was fabricated as follows. A capillary column (10 m 0.25 mm, i.d.) was filled with a dopamine solution (1.2 mg/mL dopamine in 10 mmol/L Tris–HCl buffer, pH 8.5) and
http://dx.doi.org/10.1016/j.cclet.2015.05.054 1001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054
G Model
CCLET-3417; No. of Pages 3 Y.-F. Zhang et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
2
stayed for 24 h at room temperature. After this, the solution in the capillary was flushed out and washed with water for 5 min and dried under nitrogen. The obtained PDA coating showed orderly crumpled morphology (Fig. S1 in Supporting information). Then, the column with PDA was further statically coated with the suspension of CB7 stationary phase in dichloromethane (0.25%, w/v) at room temperature. Briefly, after the column was filled with the suspension, one end of the capillary was sealed and the other was connected to a vacuum system to gradually remove the solvent. The coated capillary columns were then conditioned from 40 to 180 8C at the rate of 1 8C/min and held at the high-end temperature for 7 h under a constant flow of nitrogen at 1 mL/min. CB7 column without PDA was prepared by the method described in the reference [8]. 3. Results and discussion 3.1. McReynolds constants and column efficiency Column efficiency of PDA-CB7 column was determined by isothermal determination of n-dodecane at 120 8C and evaluated by the theoretical plate number per meter. As a result, PDA-CB7 column exhibited a column efficiency of 2823 plates/m. McReynolds constants were determined at 120 8C by using five probe compounds, namely benzene (X0 ), 1-butanol (Y0 ), 2-pentanone (Z0 ), 1-nitropropane (U0 ) and pyridine (S0 ). Table 1 lists the obtained McReynolds constants for PDA-CB7 column as well as CB7 column. As shown, PDA-CB7 column showed average polarity of 122, slightly higher than that of CB7 column, suggesting their weakly polar nature. Relatively, PDA-CB7 column had higher Y0 , U0 and S0 values than CB7 column, suggesting its slightly stronger H-bonding and dipole–dipole interactions with H-bonding analytes than CB7 column possibly due to the presence of PDA coating. 3.2. Separation performance Separation performance of PDA-CB7 column was investigated by separations of analytes of different variety, including n-alkanes, halogenated benzenes and the Grob test mixture. Fig. 1 shows the separations of n-alkanes (a) and halogenated benzenes (b) on PDACB7 column, showing its good separation performance for common analytes. To examine its performance for critical analytes, the Grob mixture, the most challenging mixture in GC, was separated, while a CB7 column without PDA and a commercial DB-35MS column were used for comparison (Fig. 2).
250
(a) 1
200
Columns
X0
Y0
Z0
U0
S0
Sum
Average
PDA-CB7 CB7 DB-35MS
33 11 102
187 146 142
97 78 145
169 124 219
122 82 178
608 441 786
122 88 157
X0 : benzene, Y0 : 1-butanol, Z0 : 2-pentanone, U0 : 1-nitropropane, S0 : pyridine.
As evidenced in Fig. 2, PDA-CB7 and CB7 columns shared the same elution order for the analytes but differed from the commercial column for some of them. Noticeably, PDA-CB7 column exhibited good resolution for most of them, especially for the peak pairs of n-undecane/1-nonanal/1-octanol (peaks 3/4/ 5, a3/4 = 1.03, a4/5 = 1.06) and dicyclohexylamine/methyl undecanoate (peaks 10/11, a9/10 = 1.01), which completely coeluted on CB7 column. This finding suggested the partial contribution of PDA coating to the separation. The analytes of n-undecane, 1-nonanal and 1-octanol share a quite close boiling point but have different polarity. PDA-CB7 column exhibited higher selectivity for these analytes probably due to its additional interactions with these analytes via H-bonding and dipole–dipole interactions. These additional interactions may be minor but did make a difference when working together with CB7 stationary phase in achieving improved separations of the indicated analytes. In contrast to the commercial column, PDA-CB7 column switched the elution order of two peak pairs, namely 1-nonanal/1-octanol (peaks 4/5) and 2,6dimethylaniline/2-ethylhexanoic acid (peaks 7/8). The later elution of 1-octanol and 2-ethylhexanoic acid on PDA-CB7 column indicated their stronger H-bonding and dipole–dipole interactions with PDA-CB7 coating, which may also lead to their tailing peaks. Additionally, PDA-CB7 column showed wider peaks due to its lower column efficiency which might be attributed to the adsorption nature of PDA-CB7 column for the separations. The above findings demonstrate that PDA precoating is feasible in GC column fabrication and also helpful for improving the resolving ability of the as-fabricated column for critical analytes such as aldehydes and amines. 3.3. Separation repeatability and thermal stability Furthermore, separation repeatability of PDA-CB7 column was also examined by separation of a mixture of 11 analytes and evaluated by relative standard deviations (RSD %) in retention times of the analytes. The obtained RSD values are listed in Table S1, showing 0.01–0.05% for intra-day (n = 6), 0.06–0.69% for inter-day
600
8
(b)
3
2
3
6 4
7
1
5
400 2
150 pA
pA
Table 1 McReynolds constants of PDA-CB7, CB7 and DB-35MS capillary columns.
4
5
200
100
50 0
2
4
6 Time (min)
8
10
0 0
2
4
6
Time (min)
Fig. 1. Separations of n-alkanes (a) and halogenated benzenes (b) on PDA-CB7 column. Peaks for (a): (1) nonane, (2) decane, (3) undecane, (4) dodecane,. (5) tridecane, (6) tetradecane, (7) pentadecane, (8) hexadecane; for (b): (1) chlorobenzene, (2) bromobenzene, (3) 1,4-dichlorobenzene, (4) 1,2-dichlorobenzene, (5)1,2,4-trichlorobenzene. Temperature programs: (a) 40 8C (1 min) to 130 8C at 10 8C/min and (b) 40 8C (1 min) to 90 8C at 10 8C/min.
Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054
G Model
CCLET-3417; No. of Pages 3 Y.-F. Zhang et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
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9
10
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5
2
400
11
200
pA
500
1
4
1
100
6
9
12
8
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1
200 100
50 05101520
024681012
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7
400
7
100 8
9 10 5
10+11
4+56
150
DB-35MS11 12
3
500
3
300 6
2
600
12
pA
3
200
700
250
2
600
pA
CB7
PDA-CB7
3
48
02468101214
Time (min)
Time (min)
Fig. 2. Separations of the Grob mixture on PDA-CB7, CB7 and DB-35MS capillary columns. Peaks: (1) 2,3-butanediol, (2) n-decane, (3) n-undecane, (4) nonanal, (5) 1-octanol, (6) 2,6-dimethylphenol, (7) 2,6-dimethylaniline, (8) 2-ethylhexanoic acid, (9) methyl decanoate, (10) dicyclohexylamine, (11) methyl undecanoate, (12) methyl dodecanoate. Temperature programs: 40 8C (1 min) to 160 8C at 10 8C/min for PDA-CB7 and DB-35 columns and 40 8C (1 min) to 160 8C at 5 8C/min for CB7 column.
(n = 6) and 2.7–6.4% for between-column (n = 3), respectively. These results demonstrated the good repeatability of PDA-CB7 column for GC separations. In addition, the column also exhibited good thermal stability up to 270 8C. 4. Conclusion This work introduced PDA coating into GC column fabrication and presented the first example of employing PDA coating as an efficient GC column pretreatment method. This work demonstrates that PDA coating not only served for the pretreatment but also made a partial contribution to GC separations. Integration of PDA coating with CB7 achieved enhanced resolving ability in contrast to neat CB7 column, suggesting the possible synergic interactions PDA coating with CB7 stationary phase. This work shows that PDA coating for GC column pretreatment is facile and efficient and has advantages over the conventional method in separation performance. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 21075010) and the 111 Project B07012 in China.
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Please cite this article in press as: Y.-F. Zhang, et al., Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.054