Electronic Supplementary Material
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Extraction and determination of polybrominated diphenyl ethers in water and
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urine samples using microextraction via solidified floating organic drop along
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with high performance liquid chromatography
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Huanqiang Liu1, Minghua Zhang1, Xuedong Wang1*, Wenwei Wang1, Meiping Ma1
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Yanyan Li1, Huili Wang2*
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College of Environmental Science and Public Health, Wenzhou Medical College,
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University-Town, Wenzhou, Zhejiang, China 325035
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Zhejiang, China 325035
College of Life Science, Wenzhou Medical College, University-Town, Wenzhou,
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∗ Corresponding author, E-mail: whuili@163.com, Tel: 86-577-86699652, Fax:
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86-577-86699122
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Effect of sample solution temperature
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The temperature was an important parameter to influence extraction efficiency. The
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selection of temperature was studied over the range of 30-70 °C. As shown in Fig. S1,
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the peak areas for six congeners did not significantly increased from 30 to 40 °C.
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However, it obviously increased from 50-60 °C for six congeners. Especially for BDE
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183 and 209, a sharply increasing trend was observed. Solution temperature affects
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the extraction kinetics. At higher temperatures diffusion coefficients and mass transfer
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of analytes from sample to the organic solvent increase and the time required to reach
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equilibrium decreases. However, when the temperature increased to 70 °C, the
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over-pressurization of the sample vial made the extraction system unstable, and also
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the finally floating organic drop formed in ice bath was very little. Therefore, the
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sample vial temperature was held at 60 °C in the further experiments.
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Fig. S1 The effect of the sample solution temperature .Conditions: strring rate : 900
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rpm; extraction solvent volume: 25 μL; sample volume: 40 mL; extraction time: 25
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min; and without salt addition.
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Effect of stirring rate
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Sample agitation has an important role in enhancing extraction efficiency and
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reducing extraction time. On the basis of penetration theory of solute mass transfer,
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the aqueous-phase mass-transfer coefficient increases with increasing the stirring rate.
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In this study, the effects of different stirring rates (300, 500, 700, 900 and 1100 rpm)
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were investigated on extraction efficiencies. As can be seen from Fig. S2, the peak
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areas increased gradually with the stirring rate from 300 up to 900 rpm. When the
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stirring rate further increased, the peak area decreased and the system was unstable.
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According to the previous results, we selected 900 rpm as the optimum stirring rate.
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Fig. S2 Effect of stirring rate. Conditions: sample solution temperature: 60 ℃;
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extraction solvent volume: 25 μL; sample volume: 40 mL; extraction time: 25 min;
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and without salt addition.
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Effect of extraction time
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To increase precision and sensitivity of SFOME pretreatment method, it is necessary
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to select an appropriate exposure time to guarantee the achieving of equilibrium
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between aqueous and organic phase. A series of experiments were carried out and the
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extraction time profile was obtained by plotting the peak area versus the extraction
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time in the range of 5-30 min under the previously described conditions. As shown in
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Fig. S3, the highest peak area occurred at 25 min. As a result, this time was chosen as
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the optimal extraction time.
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Fig. S3 Effect of extraction time. Conditions: stirring rate, 900 rpm; sample solution
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temperature, 60℃; extraction solvent volume, 25 μL and without salt addition.
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Effect of ionic strength
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Addition of salt into the sample solution can improve extraction efficiency of analytes
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due to salting-out effect. However, by increasing salt concentration, diffusion of
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analytes towards the organic solvent becomes more and more difficult. In addition,
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salt dissolved in water might have changed the physical properties of the Nernst
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diffusion film and reduced rate of diffusion of the target analytes into the drop. In
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order to research ionic effect, the different NaCl concentrations (0-5%, w/v) of the
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sample solution were investigated (Fig. S4). The results showed the different salt
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concentrations had not significant effect on extraction efficiency of five PBDE
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congeners with an exception of declining for BDE 99. After taking all factors into
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consideration, NaCl was not added in this study.
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Fig. S4 Effect of ionic strength. Conditions: stirring rate, 900 rpm; sample solution
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temperature, 60℃; extraction solvent volume, 25 μL and extraction time, 25 min.