Electronic Supplementary Material

Improved microextraction of selected triazines using polymer monoliths modified with carboxylated multi-walled carbon nanotubes

Beatriz Fresco-Cala, Soledad Cárdenas, Miguel Valcárcel*

Department of Analytical Chemistry, Institute of Fine Chemistry and Nanotechnology, Marie Curie Building, Campus of Rabanales, University of Córdoba, 14071, Córdoba, Spain.

*Corresponding author. Phone and fax: +34 957218616 email:

Evaluation of the variables affecting to the microextraction process

The variables directly related with the extraction step were studied using aqueous standards containing the selected triazines at a concentration of 1 µg·mL-1. The initial experimental conditions for the microextraction process were: 4.8 mL of aqueous standard pumped at 0.3 mL·min-1 and an elution with 500 µL of methanol at a flow rate 0.1 mL·min-1.

The first variable studied the sample flow rate. A sample volume of 4.8 mL was pumped at 0.3, 0.4 and 0.5 mL·min-1. As it was expected, the best results in terms of peak area corresponded to 0.3 mL·min-1 as it maximized the contact time between the analyte and the sorbent (Fig. S1). Lower flow-rates were not evaluated as they negatively affected to the sample throughput.

The next variable evaluated was the sample volume within the interval 1.5-6 mL. As it can be seen in Fig. S2, the maximum extraction efficiency for the target triazines was achieved for a volume of 3 mL, decreasing over this value due to a breakthrough effect.

Finally, the elution volume was tested in range of 100-500 µL. The flow rate was maintained at 0.1 mL·min-1 and the methanolic extract was collected in a 1.5 mL glass vial. Quantitative elution was obtained for a volume of 200 µL.

Fig. S1 Effect of the sample flow rate on the extraction of target analytes.

Fig. S2 Effect of the sample volume on the extraction of target analytes.

Table S1. Schematic representation and transmission electron microscopy (TEM) images of the three carbon nanostructures.

Carbon nanoparticle / Structure / TEM images
SWNH / /
SWCNT / /
MWCNT / /