Electronic Supporting Information on the MicrochimicaActa publication entitled
Microextraction in packed syringe by using a three-dimensional carbon nanotube/carbon nanofiber‒graphene nanostructurecoupled to dispersive liquid-liquid microextraction for the determination of phthalate esters in water samples
AmirhassanAmiri*,a,Ferial Ghaemi b
aDepartment of Chemistry, Faculty of Sciences, Hakim Sabzevari University, 9617976487, Sabzevar, Iran
bInstitute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
*Corresponding author:
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Tel: +98 51 44013323
Fax: +98 51 44013170
Optimization of MEPS parameters
Desorption conditions
To ensure effective elution of the trapped analytes from the sorbent, the influence of both desorption solvent and its volume were investigated.An ideal elution solvent should be strong enough to elute all the target compounds from the sorbent.Different organic solvents including acetone, acetonitrile, ethanol and methanol were examined. The result showed that methanol exhibited the best performance (Fig. S1). Therefore, methanol was finally adopted as optimum elution solvent for overall subsequent experiments.
Fig. S1. Effect of desorption solvent on extraction efficiency. Extraction conditions: sample volume, 8 mL; sorbent amount, 2 mg;, eluent volume, 0.5mL; sample loading, 50 cycles of draw-eject; extraction solvent, chlorobenzene; volume of extraction solvent, 25 μL.
To achieve the quantitative recovery of the adsorbed analytes, the effect of the eluent volume was also tested for the range of 0.25–1mL (Fig.S2). The results show that the extraction efficiency was significantly enhanced as eluent volume up to 0.75mL, and then remained constant after that. Therefore, 0.75mL of methanol was selected to ensure complete elution of analytes for further experiments.
Fig S2.Effect of elution volume on extraction efficiency.Extraction conditions: sample volume, 8 mL; sorbent amount, 2 mg; eluent, dichloromethane; sample loading, 50 cycles of draw-eject; extraction solvent, chlorobenzene; volume of extraction solvent, 25 μL.
Influence of draw–eject cycles on extraction efficiency
In order to optimize the way of sample loading, the multiple draw-eject cycle mode was tested.Sample loading can be done once or more depending on sample concentration and if pre-concentration of the targeted analytes is required. To obtain the sample loading profiles of PEs by MEPS, the number of draw-eject cycles was varied from 30 to 80 times. The draw-eject procedure was applied to the extraction of 8 mL of sample with an analyte concentration of 50 ng mL−1. As shown in Fig. S3, the extraction efficiencies for all compounds under investigation increased using 70 cycles. Afterward, the extraction efficiency did not change significantly for most of the analytes.
Fig S3.Effect of draw–eject number of sample through the sorbent on the extraction efficiency. Extraction conditions: sample volume, 8 mL; sorbent amount, 2 mg; desorption solvent, 0.75mL methanol; extraction solvent, chlorobenzene; volume of extraction solvent, 25 μL.
Optimization of DLLME parameters
Effect of type and volume of the extraction solvent
For the selection of the extraction solvent, some properties must be considered. The extraction solvent should have a higher density than water, good chromatographic behavior, an extraction capability of the interested compounds and a low solubility in water. Chlorobenzene, chloroform, and tetrachloroethylene were examined in the extraction of PEs.Fig. S4 exhibits the extraction efficiencies for the tested organic solvents.As you can see from Fig. S4, chlorobenzene showed the best extraction performance among the three extraction solvents in terms of analyte peak areas. Therefore, chlorobenzene was selected as the extraction solvent in further experiments.
Fig S4.Effect of extraction solvent on the extraction efficiency. Extraction conditions: sample volume, 8 mL; sorbent amount, 2 mg; desorption solvent, 0.75mL methanol; sample loading, 70 cycles of draw-eject; extraction solvent, chlorobenzene; volume of extraction solvent, 25 μL.
To examine the effect of extractionsolvent volume, solutions containing differentvolumes of chlorobenzene(10, 15, 20, 25, 30, and 40 μL) weresubjected to the DLLME procedure.When the volume of chlorobenzene was increased from 10 to 20μL, the extraction efficiency of target analytes was increased and decreased thereafter. The resultsindicated that the best extraction efficient was obtained when20μLchlorobenzene was used.
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