A novel magnetic ionic liquid modified carbon nanotube for the simultaneous determination of aryloxyphenoxy-propionate herbicides and their metabolites in water
Graphical abstract
Introduction
The aryloxyphenoxy-propionate herbicide (AOPP) is a kind of selective post-emergence herbicide [1], which was registered for use in controlling annual and perennial grassy weeds for many crops. They interfere with production of fatty acids needed for plant growth by inhibition of acetyl co-enzyme A carboxylase [2], and in most cases AOPPs can be rapidly deesterificated to their acidic form by plants or soil, which increases their polarity and solubility but does not influence their bioactivity [3], [4], [5]. AOPPs are toxic to aquatic organisms [6], especially fish, and could be inducers of liver toxicity and injury [7]. The widespread use contributes to their presence in the environment and positive detectable rate in surface and ground water and other environmental matrices [8], [9], and the accumulation of these herbicides may potentially destroy fish populations in natural water systems and jeopardize human health. Therefore, it is necessary to develop robust methods to simultaneously analyze AOPP and their metabolites residues in water.
Conventional methods for isolation and/or enrichment of AOPPs related chemicals from water involve liquid–liquid extraction (LLE), solid phase extraction (SPE) [9], [10], [11]. LLE is widely used traditional sample pre-treatment method for water samples. However, it is not preferred when water either contains emulsifying agents or analytes present in trace quantities. Moreover it is time consuming, requires large volume of toxic organic solvents and lacks automation. SPE is a simple technique, however it suffers from some drawbacks such as high cost and decline in performance with time. Furthermore, it is hard to find a robust cartridge sorbent for both ester and acid. In recent years, a lot of microextraction techniques have been used in extraction of AOPPs, such as solvent microextraction (SME) [8], [12], [13], microextraction in packed syringe (MEPS) [14] and dispersive liquid–liquid microextraction (DLLME) [15]. Although SME and DLLME are less solvent-consuming than conventional methods, they still require adjusting the pH of the sample before simultaneously extracting ester and acid from water.
Dispersive magnetic solid-phase extraction (d-MSPE) is an excellent extraction method, which is a new procedure of SPE based on the use of magnetic or magnetizable sorbents. Compared with traditional SPE procedure, d-MSPE is indicated as a time and labor effective separation approach, which combines the advantages of magnetic separation technology (MST) and SPE [16], [17], [18], [19], [20]. The sorbents do not need to be packed into the SPE cartridges and the phase separation could be conveniently made by applying an external magnetic field. In d-MSPE, the sorbent plays a key role in obtaining higher enrichment efficiency of analytes. Unfortunately the common magnetic nanoparticles (MNPs), such as Fe3O4 or γ-Fe2O3, almost do not have significant adsorption efficiency. There are two ways to overcome this limitation. First, modify the surface of magnetic nanoparticles. In general, the surface of MNPs are covered with some kind of absorbent material, including poly (ethylene glycol), humic acid, etc. [17], [21], [22], [23], [24]. In this case, most sorbents on the surface of magnetic particles are hydrophobic. These hydrophobic constituents lack ability to interact with polar or ionic substances. Therefore, it makes the extraction of such analytes from environmental or biological sample difficult, which limits its application in some extent. Second, the adsorption composites were composed by MNPs and another kind of nano-sized sorbent. In recent years, the use of carbon nanotubes (CNTs) in SPE is among the most important applications of these materials in analytical science [25]. Their use is based on the properties of CNTs, for example, they have ability to establish π–π interactions as well as excellent Van der Waals interactions with other molecules, in particular with hydrophobic ones. They also possess a large surface area, especially on the outside and interstitial spaces within nanotubes bundles. Their chemical, mechanical and thermal stability should also be considered [26].
But the surface of pristine CNTs lacks active sites to interact with polar or ionic substance which limits their application in environmental pollution analysis [25]. Some research groups have used the chemical modification of CNTs, such as carboxyl multi-walled carbon nanotubes (MWCNTs-COOH) [27], [28], hydroxy multi-walled carbon nanotubes (MWCNTs-OH) [29], amino multi-walled carbon nanotubes (MWCNTs-NH2) [30], polyethylene glycol modified multi-walled carbon nanotubes (MWCNTs-PEG) and octadecylamine modified multi-walled carbon nanotubes (MWCNTs-ODA) [31], polyelectrolyte functionalized multi-walled carbon nanotubes (MWCNTs–PDDA) [32], for analysis of chemical warfare agents, polyhalogenated pollutants and pesticides. However, some of those modifications lack ability to interact with anions that makes them have no significant improvement in simultaneous analysis of ester and acid. Recently, ionic liquid modified multi-walled carbon nanotubes have been synthesized [33], [34]. They have excellent solubility and dispersibility in water and the ionic liquid on the surface of carbon nanotubes have anion exchange groups. Both of the characteristics make IL-MWCNT could be a potential sorbent for simultaneous extraction of the analytes with different polarity.
The aim of the current work is applying the proposed d-MSPE method for the simultaneous preconcentration and determination of the analytes with different polarity (four AOPP herbicides and their bioactive acid forms) in water sample. To achieve this goal, a new kind of magnetic ionic liquids modified multi-walled carbon nanotubes has been synthesized and employed as a d-MSPE sorbent. The effect of certain variables, including the amount of sorbent, pH of the sample solution, extraction time and the volume of elution solvent, on the extraction recovery (ER) of each analyte was evaluated. The proposed method was successfully applied to determine the four esters and four acids in real water samples (ground water and reservoir water). Also a comparison study with the MNPs, ionic liquids modified multi-walled carbon nanotubes and pristine multi-walled carbon nanotubes (MWCNTs) as sorbents for target analytes were conducted.
Section snippets
Standards and reagents
Diclofop-methyl (DM, 99.0%), diclofop acid (DA, 98.5%), cyhalofop-butyl (DB, 99.5%), cyhalofop acid (CA, 99.5%), quizalofop-p-ethyl (QE, 99.0%), quizalofop (QU, 99.0%), haloxyfop-methyl (HM, 99.9%) and haloxyfop acid (HA, 99.5%) were provided by the Institute for Control of Agrochemicals Ministry of Agriculture, and the chemical structures are shown in Fig. 1. The organic solvents used for HPLC determination (via acetonitrile, methanol, formic acid; all HPLC grade) were supplied by Fisher (New
Characterization of IL-MWCNT and m-IL-MWCNT
In order to confirm the successful synthesized IL-MWCNT, FT-IR spectrometry, TME and EDX were performed. In the IR spectrum of IL-MWCNT, the CO band of carboxylic acid group at 1625 cm−1 in o-MWCNT shifted to 1557 cm−1, indicating the formation of the amide bond, while the CN mode of the imidazole ring was also observed at 1467 cm−1 (see Fig. S2 in the Supporting information). TEM gave important morphological information on the hybrid materials and energy dispersive X-ray spectroscopy (EDX)
Conclusions
The d-MSPE method was used for the determination of four AOPPs and their metabolites in environmental samples based on imidazolium salt-based ionic liquids (ILs)-modified carbon nanotubes as sorbent. This was a first analytical report in which the simultaneous enrichment and determination of four AOPPs and their metabolites with different polarity were presented. The method was environmentally friendly because only near 2 mL of methanol was used. Good linearity, reproducibility and lower
Acknowledgements
This work was supported by A Foundation for the Author of National Excellent Doctoral Dissertation of PR China, Program for New Century Excellent Talents in University(NCET09-0738), the National Natural Science Foundation of China (21277171, 21337005, J1210064), the New-Star of Science and Technology supported by Beijing Metropolis, Program for New Century Excellent Talents in University and Program for Changjiang Scholars and Innovative Research Team in University.
References (36)
- et al.
Solid-phase extraction followed by high-performance liquid chromatography–ionspray interface–mass spectrometry for monitoring of herbicides in environmental water
J. Chromatogr. A
(2000) - et al.
Negative electrospray ionization ion mobility spectrometry combined with microextraction in packed syringe for direct analysis of phenoxyacid herbicides in environmental waters
J. Chromatogr. A
(2012) - et al.
Rapid and effective sample clean-up based on magnetic multiwalled carbon nanotubes for the determination of pesticide residues in tea by gas chromatography–mass spectrometry
Food Chem.
(2014) - et al.
Rapid magnetic solid-phase extraction based on magnetite/silica/poly(methacrylic acid-co-ethylene glycol dimethacrylate) composite microspheres for the determination of sulfonamide in milk samples
J. Chromatogr. A
(2010) - et al.
Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates
J. Chromatogr. A
(2013) - et al.
Application of derivatized magnetic materials to the separation and the preconcentration of pollutants in water samples
Trends Anal. Chem.
(2011) - et al.
Preparation of hydrophilic carbon-functionalized magnetic microspheres coated with chitosan and application in solid-phase extraction of bisphenol A in aqueous samples
Talanta
(2012) - et al.
Mixed hemimicelles solid-phase extraction of chlorophenols in environmental water samples with 1-hexadecyl-3-methylimidazolium bromide-coated Fe3O4 magnetic nanoparticles with high-performance liquid chromatographic analysis
Anal. Chim. Acta
(2012) - et al.
n-Octadecylphosphonic acid grafted mesoporous magnetic nanoparticle: preparation characterization application in magnetic solid-phase extraction
J. Chromatogr. A
(2010) - et al.
Carbon nanotubes applications in separation science: a review
Anal. Chim. Acta
(2012)
Fast microextraction of phthalate acid esters from beverage, environmental water and perfume samples by magnetic multi-walled carbon nanotubes
Talanta
Preparation of multi-walled carbon nanotubes functionalized magnetic particles by sol–gel technology and its application in extraction of estrogens
Talanta
Polyelectrolyte functionalized multi-walled carbon nanotubes as strong anion-exchange material for the extraction of acidic degradation products of nerve agents
J. Chromatogr. A
Detection of the herbicide fenoxaprop-p-ethyl, its agronomic safener isoxadifen ethyl and their metabolites residue in rice
Qual. Assur. Saf. Crops Foods
Herbicides inhibiting acetyl-CoA carboxylase
Biochem. Soc. Trans.
Metabolism and selectivity of diclofop-methyl in wild oat and wheat
J. Agric. Food Chem.
Metabolism of diclofop-methyl in root-treated wheat and oat seedlings
J. Agric. Food Chem.
Selectivity of diclofop-methyl between wheat and wild oat: growth and herbicide metabolism
Physiol. Plant.
Cited by (57)
Nanomaterials and their application in microbiology disciplines
2023, Advances in Smart Nanomaterials and their ApplicationsIonic liquid-based magnetic nanoparticles for magnetic dispersive solid-phase extraction: A review
2022, Analytica Chimica ActaType of green solvents used in separation and preconcentration methods
2020, New Generation Green Solvents for Separation and Preconcentration of Organic and Inorganic SpeciesNanotechnology and remediation of agrochemicals
2020, Agrochemicals Detection, Treatment and Remediation: Pesticides and Chemical Fertilizers