No abstract

No abstract

In the present work, the performance of carbon nanotubes (c-CNTs) functionalized polydimethylsiloxane (PDMS) based coatings as extractive phases for in-tube solid phase microextraction (IT-SPME) coupled to Capillary LC (CapLC) has been evaluated. Carboxylic-single walled carbon nanotubes (c-SWNTs) and carboxylic-multi walled carbon nanotubes (c-MWNTs) have been immobilized on the activated surface of PDMS capillary columns. The effect of different percentages of diphenyl groups in the PDMS extractive phase has also been evaluated. The extraction capability of the capillary columns has been tested for different organic pollutants, nitrogen heterocyclic compounds and polycyclic aromatic compounds (PAHs). The results indicated that the use of the c-CNTs-PDMS capillary columns improve pyriproxyfen and mainly PAH extraction. Triazines were better extracted by unmodified TRB-35 and modified c-CNTs-PDMSTRB-5. The results showed that the extraction capability of the c-CNT capillary columns depends not only on the polarity of the analytes (as it occurs with PDMS columns) but also on the interactions that the analytes can establish with the immobilized c-CNTs on the PDMS columns. The extraction efficiency has been evaluated on the basis of the preconcentration rate that can be achieved, and, in this sense, the best c-CNTs-PDMS capillary column for each group of compounds can be proposed.

This paper describes a new method for the determination of polar triazines, including some degradation products, which combines online in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography with UV-diode array detection (DAD). Different extractive coatings have been evaluated for IT-SPME, a capillary column with a polydimethylsiloxane (PDMS) coating, and the same coating modified with carboxylated single-wall carbon nanotubes (c-SWCNTs) and carboxylated multiwall carbon nanotubes (c-MWCNTs). On the basis of the results obtained, a new method is presented for the identification and determination of triazines in water samples. A careful selection of the eluent composition provides the required selectivity and sensitivity for the quantification of the target analytes, even those highly polar (log K ow ≤ 2.3). The proposed conditions have been successfully used for the quantitation of the analytes in the 0.25-50.0 μg L(-1) range. The limits of detection (LODs) are in the 0.02-0.1 μg L(-1) range, and the intraday and interday relative standard deviation (RSD) coefficients are ≤9 and ≤17 %, respectively. The reliability of the described method has been tested by analyzing several real water samples. The proposed method can be considered an environmentally friendly and cost-effective alternative for routine monitoring of triazines and their degradation products in waters.

Abstract:In the present work the extraction efficiency of in-tube solid-phase microextraction (IT-SPME) for polar herbicides has been evaluated using extractive capillaries coated with different polymeric sorbents. For this purpose, aqueous solutions of herbicides with a wide range of polarities, including some highly polar compounds (log K ow < 1), have been directly processed by IT-SPME coupled on-line to capillary liquid chromatography with UV-diode array detection. For extraction, commercially available capillary columns coated with polydimethylsiloxane (PDMS) and polyetilenglicol (PEG)-based phases have been used, and the results have been compared with those obtained with a synthesized tetraethyl orthosilicate (TEOS)-trimethoxyethylsilane (MTEOS) polymer, as well as the same polymer reinforced with silica nanoparticles (SiO 2 NPs). The SiO 2 NPs functionalized TEOS-MTEOS coating provided the best results for most herbicides, especially for the most polar compounds. On the basis of the results obtained, conditions for the quantification of the herbicides tested are described using a SiO 2 NPs reinforced TEOS-MTEOS coated capillary. The proposed method provided satisfactory linearity up to concentrations of 200 µg/L. The precision was also suitable, with relative standard deviations (RSDs) values ≤9% (n = 3), and the limits of detection (LODs) were within the 0.5-7.5 µg/L range. The method has been applied to different water samples and the extract obtained from an agricultural soil.