Carbon Nanotubes As Sorbent For Solid Phase Extraction In The Sequential Injection System

PETR SOLICH; LUCIE ZELENÁ; IVANA SRÁMKOVÁ; DALIBOR SATÍNSKÝ; CAROLINA C. ACEBAL; BEATRIZ S. FERNÁNDEZ BAND; HANA SKLENÁROVÁ

Simposio; 16th International Symposium on Advances in Extraction Technologies; 2014

Carbon nanotubes (CNTs) can be described as a graphite sheet rolled up into a nanoscale-tube (single-wall CNTs) or with additional graphene tubes around (multi-wall CNTs) [1]. CNTs were discover by Iijima and until now they have different applications, e.g. materials for sensors or biosensors, pseudo stationary phases in chromatography or sorbents for solid phase extraction (SPE) [1]. CNTs were tested before for clean-up of samples with complex matrices and/or for pre-concentration of trace analytes [2, 3]. The aim of this work was to develop an automated SPE method for determination of furosemide in sequential injection (SIA) system. The method based on SPE on-line coupled to the SIA with spectrophotometric detection of the analyte was optimized. Multi-wall CNTs were used as a sorbent packed in SPE cartridge and connected to the SIA system in the way from the selection valve to the flow cell of the detector using T-junction. The additional piston pump was used to wash the SPE micro-column with organic solvent for activation and elution steps. The procedure consisted of the following steps: 1) pre-conditioning of SPE column and activation of CNTs with pure organic solvent, 2) washing the column with water, 3) loading of sample, 4) washing the column with water (removal of matrix impurities), 5) drying of the column with air stream (removal of water), 6) elution of analyte from SPE column with pure organic solvent followed by detection of eluate. Different steps were optimized to achieve the best conditions for automation of SPE procedure. Tested pH of furosemide standard solutions (2 and 10 µg/ml) was 4.70 and 2.00 and pH 2.00 was chosen to increase interaction between the analyte and sorbent. Two different organic solvents, acetonitrile and methanol, were applied. Different volumes of pure organic solvents for elution step were tested and results proved that 2 ml of solvent is volume high enough to elute the trapped analyte. The flow-rate for each step, mainly sampling and elution, was optimized in range of 5 ? 20 µl/s. The selected flow-rates for sampling and elution steps were 5 and 10 µl/s, respectively. The remaining steps were carried out with the flow-rate of 20 µl/s. Sample volume optimization was carried out in the range of 100 ? 2000 µl. For next experiments (repeatability tests) the sample volume of 1500 µl was used. Repeatability values (% RSD, n = 6) were 8.81% and 4.67% for acetonitrile and methanol as elution solvents, respectively. References [1] M. Trojanowicz, Analytical applications of carbon nanotubes: a review, Trends Anal. Chem. 25 (2006) 480-489. [2] V. H. Springer, A. G. Lista, A simple and fast method for chlorsulfuron and metsulfuron methyl determination in water samples using multiwalled carbon nanotubes (MWCNTs) and capillary electrophoresis, Talanta 83 (2010) 126-129. [3] V. H. Springer, F. Aprile, A. G. Lista, Determination of sulfonylureas in cereal samples with electrophoretic method using ionic liquid with dispersed carbon nanotubes as electrophoretic buffer, Food Chemistry 143 (2014) 348-353.