Multi-walled carbon nanotubes–dispersive solid-phase extraction combined with nano-liquid chromatography for the analysis of pesticides in water samples

Abstract

In this work, the simultaneous separation of a group of 12 pesticides (carbaryl, fensulfothion, mecoprop, fenamiphos, haloxyfop, diclofop, fipronil, profenofos, fonofos, disulfoton, nitrofen, and terbufos) by nano-liquid chromatography with UV detection is described. For the analyses, a 100 μm internal diameter capillary column packed with silica modified with phenyl groups was used. Experimental parameters, including the use of a trapping column for increasing the sensitivity, were optimized and validated. A preliminary study of the applicability of a rapid and practical dispersive solid-phase extraction (DSPE) procedure was developed for the extraction of some of these pesticides (carbaryl, fensulfothion, fenamiphos, fipronil, profenofos, fonofos, disulfoton, nitrofen, and terbufos) from Milli-Q water samples using multi-walled carbon nanotubes (MWCNTs). The method was validated through a recovery study at three different levels of concentration, obtaining limits of detection in the range 0.016-0.067 μg/L (below European Union maximum residue limits) for the majority of the pesticides. In this work, MWCNTs were reused up to five times, representing an important reduction of the waste of stationary phase. Furthermore, DSPE permitted a clear diminution of the total sample treatment time with respect to conventional SPE.

Pesticide analysis at ppt concentration levels: coupling nano-liquid chromatography with dielectric barrier discharge ionization-mass spectrometry

“…Zhu et al [8] used a nano-LC system based on a microfluidic chip and an enrichment column to analyze illicit drugs and metabolites in human hair with tandem mass spectrometry, with limits of detection in the low picogram-per-milligram level of hair sample. A multi-walled carbon nanotube-dispersive solid-phase extraction was also used [9] for the extraction of 12 pesticides prior to nano-LC-UVanalysis. In that work, a trapping column was employed to increase the overall sensitivity.…”

Theory and Practice of UHPLC and UHPLC–MS

“…Most of the articles regard the analysis of pesticides (Asensio-Ramos et al, 2011;Moliner-Martínez et al, 2011b;Gure et al, 2013;Otieno et al, 2013;Lerma-García et al, 2013;Berlioz-Barbier et al, 2014), but also other emerging pollutants have been determined with miniaturized techniques, such as perfluorinated compounds (Berlioz-Barbier et al, 2014;Onghena et al, 2012), phthalates (JornetMartínez et al, 2014;Muñoz-Ortuño et al, 2014), or hormones (Berlioz-Barbier et al, 2014;D'Orazio et al, 2016b;Kozlík et al, 2011), most of them in simple matrices (different types of waters). In a few other examples, pesticides (Otieno et al, 2013) and di-(2-ethylhexyl) phthalate were determined in sediments, multiclass emerging pollutants in benthic invertebrates (Berlioz-Barbier et al, 2014), carbonyl compounds in wastewater filters, and biocides in industrial formulations (Prieto-Blanco et al, 2016).…”

“…To obtain better sensitivity by means of online strategies, different approaches have been used in this field. For instance, on two occasions a 2D commercial system has been employed to preconcentrate the analytes, injecting a high volume of sample onto a trap column (1D), from which they are later eluted onto the analytical column (second dimension (2D)) (Asensio-Ramos et al, 2011;Berlioz-Barbier et al, 2014). A simpler and cheaper solution, on-column focusing, was applied by D 'Orazio et al (2016b), who injected a high volume of sample diluted in a solvent with lower elution strength than that of the mobile phase directly on the analytical column, preconcentrating the analytes on the top of the column.…”

Pesticide residue analysis in cereal-based baby foods using multi-walled carbon nanotubes dispersive solid-phase extraction

“…dSPE has been mainly used for clean-up purposes by adding a suitable sorbent to the organic matrix solution containing the analytes and potential interferences, removing the last of them, rather than for the performance of the extraction. Even so, some works have shown the use of the dSPE mode with good results using different types of sorbents [20][21][22] and, as far as we know, very few [23][24][25][26][27] have used multi-walled carbon nanotubes (MWCNTs) for dSPE. Two of these works have been developed by our group.…”

“…Two of these works have been developed by our group. In one of them, 9 pesticides were analyzed in water samples by nano-LC [23] and in the other, 11 quinolone antibiotics were determined in environmental waters by CE [24] providing promising results. Moreover, only in one occasion have MWCNTs been used as sorbents in dSPE for the analysis of foods, in particular estrogens in milk [26].…”