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Supporting information
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Quantitative on-line concentration for capillary electrophoresis with
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inkjet sample introduction technique
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Ying Rang, Hulie Zeng, Hizuru Nakajima, Shungo Kato, Katsumi Uchiyama*
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Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo
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Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
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Corresponding author:
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Prof. Dr. Katsumi Uchiyama
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Department of Applied Chemistry
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Graduate School of Urban Environmental Sciences
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Tokyo Metropolitan University
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Minamiohsawa, Hachioji, Tokyo 192-0364, Japan
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Phone: +81 42 677 2835, FAX +81 42 677 2821
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Table of Contents:
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Figure S1. Time course variation of the weight of total droplets ejected under evaporation
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conditions.
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Table S1. Calculation of the average weight and volume of each droplet for standard sample
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Table S2. Ratio of sample zone length to total length of the capillary
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Table S3. Linearity of ejected droplet number in injection
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Figure S2. Linear relationship between peak area and sample concentration for methylxanthines
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by quantitative on-line concentration CE.
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Figure S1. Time course variation of the weight of total droplets ejected under evaporation
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conditions. No. 1 to 4 represented four ejections of the same solution by inkjet microchip,
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each time 10000 droplets [1].
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In Fig. S1, the temperature was 20℃ and humidity was 30 RH%. In the measurement of
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weight for each sample droplet in inkjet injection (25 V, 24 µs), a 0.1 mM mixed standard solution
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of theobromine, caffeine and theophylline was used. A bottle partly filled with water was placed in
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the balance, and the inkjet microchip was fixed right above the bottle. The balance was reset after
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the value on the balance reached a constant value, then 10000 Droplets of the standard solution
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were ejected for each time and the procedure repeated for 4 times. 4 Series of linear relationships
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between time and weight of the total ejected sample droplets under evaporation conditions were
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obtained.
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Table S1. Calculation of the average weight and volume of each droplet for the standard
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sample [1]
Ejection No.
2~1
3~2
4~3
Average
Density (g/mL)
Volume (pL)
Time (s)
0.678
0.680
0.684
/
10,000 droplets
1 droplet
Wn+1 (g)
Wn (g)
ΔWn (g)
3.638
3.641
3.642
3.640
3.635
3.637
3.640
3.637
1.0039
310 ± 53.7
3.3×10-7
3.5×10-7
2.5×10-7
3.1×10-7
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In Table S1, No. 1 to 4 represented four ejections of same solution by inkjet microchip, each
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time 10000 droplets. ΔWn in the ejection No. 2~1, 3~2 and 4~3 represented the weight of ejected
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10000 droplets in second, third and fourth ejection (without the influence of evaporation).
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In Table S1, the temperature was 20℃ and the relative humidity was 30 RH%. In the
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measurement of the weight of each sample droplet in the inkjet injection (25 V, 24 µs), 0.1 mM of
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a mixed standard solution of theobromine, caffeine and theophylline was used. Depending on
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Verkouteren et al’s method [1], ΔW1 (weight for one droplet, the difference between W2 and W1
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divided by 10000) was 3.312×10-7 g. Repeated 3 times from No. 2~1 to No. 4~3, and the average
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weight of one sample droplet was calculated. Lastly, the volume of each droplet of the standard
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sample solution was calculated to be 310 ± 53.7 pL. Since the whole procedures for measuring the
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average volume of one ejected droplet were under low-humidity conditions, the influence of
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evaporation was not neglectable and this resulted in a high standard deviation of the average
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volume of one ejected droplet.
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Table S2. Ratio of sample zone length to total length of the capillary
Droplet
number
5
10
25
50
75
100
250
400
500
750
1000
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60
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Sample volume
(mL)
Length of the
sample zone
(cm)
Ratio of the
sample zone
length* (%)
1.55×10-6
3.10×10-6
7.74×10-6
1.55×10-5
2.32×10-5
3.10×10-5
7.74×10-5
1.24×10-4
1.55×10-4
2.32×10-4
3.10×10-4
0.08
0.16
0.39
0.79
1.18
1.58
3.94
6.23
7.89
11.83
15.77
0.15
0.30
0.76
1.52
2.28
3.04
7.61
12.02
15.22
22.84
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*Ratio of the sample zone length (%) = (the length of sample zone/the total length of the
capillary) ×100%.
In Table S2, temperature was 20℃ and humidity was 30 RH%. Capillary: I.D. 50 µm, O.D.
375 µm; Total length 51.8 cm, effective length 43.3 cm; cross sectional area 1.96×10-5 cm2.
Table S3. Linearity of ejected droplet number in injection
Methylxanthine
Linearity* (5 – 100 droplets)
Theobromine
Caffeine
Theophylline
y = 12634.2x + 123.0
y = 17331.2x - 888.4
y = 24194.2x - 544.7
*x: droplet number; y: peak area (μV.s)
R2
0.987
0.968
0.984
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Figure S2. Linear relationship between peak area and sample concentration for
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methylxanthines by quantitative on-line concentration CE. Methylxanthines were analyzed under
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optimized quantitative CE conditions.
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References
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[1] Verkouteren R. M., Verkouteren J. R., Anal. Chem., 2009, 81, 8577-8584.