Clean-up of triazines in vegetable extracts by molecularly-imprinted solid-phase extraction using a propazine-imprinted polymer

An analytical methodology based on a molecularly imprinted solid-phase extraction (MISPE) procedure was developed for the determination of several triazines (atrazine, simazine, desethylatrazine (DEA), desisopropylatrazine (DIA), and propazine) in vegetable samples. A methacrylic acid-based imprinted polymer was prepared by precipitation polymerisation using propazine as template and toluene as porogen. After removal of the template by Soxhlet extraction, the optimum loading, washing, and elution conditions for MISPE of the selected triazines were established. The optimised MISPE procedure was applied to the extraction of the selected triazines in pea, potato, and corn sample extracts and a high degree of clean-up was obtained. However, some remaining interferences, non-specifically and strongly bound to the polymeric matrix, appeared in the chromatogram, preventing quantification of DIA in potatoes and DIA, DEA, and propazine in corn samples. Thus, a new clean-up protocol based on the use of a non-imprinted polymer for removal of these interferences prior to the MISPE step was developed. By following the new two-step MISPE procedure, the matrix compounds were almost completely removed, allowing the determination of all the triazines selected at concentration levels below the established maximum residue limits, making the developed procedure suitable for monitoring these analytes in vegetable samples.     

Evaluation of 2-hydroxyethyl methacrylate as comonomer in the preparation of water-compatible molecularly imprinted polymers for triazinic herbicides

In this work, the preparation and evaluation of water-compatible molecularly imprinted polymers for triazines using 2-hydroxyethyl methacrylate and methacrylic acid as comonomers is described. Four sets of molecularly imprinted and non-imprinted polymers for propazine were prepared at varying monomer molar ratios (from 4:0 to 1:3), and evaluated for the recognition of several triazines directly in aqueous media. The evaluation was performed by loading 1 mL of an aqueous solution containing 500 ng of each selected triazine, washing with 500 μL of acetonitrile, and eluting with 500 μL of methanol followed by 2 × 500 μL of a solution of methanol containing 10% of acetic acid. Final determinations were performed by high-performance liquid chromatography-ultraviolet detection. Improvement in molecular recognition of triazines in water was obtained on those molecularly imprinted polymers incorporating 2-hydroxyethyl methacrylate in 3:1 or 2:2 molar ratios, being the former selected as optimum providing recoveries for propazine up to 80%. A molecularly imprinted solid-phase extraction protocol was developed to ensure that triazines-selective recognition takes place inside selective binding sites in pure water media. Finally, the developed method was successfully applied to the determination of the selected triazines in environmental waters providing limits of detection from 0.16 and the 0.5 μg/L concentration range.     

Surface modified‐magnetic nanoparticles by molecular imprinting for the dispersive solid‐phase extraction of triazines from environmental waters

Magnetic nanoparticles have been surface modified by molecular imprinting and evaluated as selective sorbents for the extraction of triazines from environmental waters. The use of propazine as template allowed us to synthesize a selective material able to simultaneously recognize and selective extract not only the template but also several other herbicides of the same family. A magnetic molecularly imprinted‐based dispersive solid‐phase extraction procedure was developed and fully optimized. Magnetic molecularly imprinted polymer particles can be easily collected and separated from liquid solvents and samples with the help of an external magnetic field, avoiding in that way any centrifugation or filtration steps, which represents a remarkable advantage over traditional procedures. Under optimum conditions, selective extraction of several triazines (cyanazine, simazine, atrazine, propazine, and terbutylazine) from environmental water samples was performed prior to final determination by high‐performance liquid chromatography with diode‐array detection. Recoveries for the studied triazines were within the range of 75.2–94.1%, with relative standard deviations lower than 11.3% (n = 3). The limits of detection were within 0.16–0.51 µg/L, depending upon the triazine and the type of sample analyzed.     

Molecularly imprinted matrix solid-phase dispersion coupled to micellar electrokinetic chromatography for simultaneous determination of triazines in soil, fruit, and vegetable samples

A simple and sensitive method for the simultaneous determination of four triazines from soil, strawberry, and tomato samples was developed by selective molecularly imprinted matrix solid-phase dispersion (MI-MSPD) coupled to micellar electrokinetic chromatography (MEKC). Using atrazine as template, the synthesized molecularly imprinted polymers (MIPs) were employed as the dispersion sorbent of MSPD to successfully extract atrazine and its analogs of simazine, ametryn, and propazine from the three different real samples, while matrix interferences were effectively eliminated simultaneously under the optimum extraction conditions. Excellent separation was achieved within 7 min by using an optimized buffer system composed of 30 mmol/L ammonium acetate, 20 mmol/L SDS, and 15% ACN at pH 9.45, obtained by orthogonal design. Good linearity was obtained in a range of 0.5-25 μg/g with the correlation coefficients R(2) ≥0.9991 except for strawberry sample within 1-25 μg/g, and limits of detection were between 12.9-31.5 ng/g in all the three samples. The average recoveries of the four triazines at three different spiked levels were ranged from 53.5 to 98.4% with the relative standard deviations of 1.28-4.89%. This method was proved convenient, costeffective, and environmental benign and could be used as an alternative tool to the existing methods for analyzing the residues of triazines in soil, fruit, and vegetable samples.     

Determination of triazines in soil leachates by solid-phase microextraction coupled to gas chromatography-mass spectrometry

A solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method was developed for the evaluation of the leachability order of selected triazines (propazine, terbuthylazine, sebuthylazine, ametryn, prometryn and terbutryn) in soil/sediment samples (organic carbon content ranging from 0.19 to 0.42%), analysing fractions collected from a soil packed microcolumn elution experiments. The procedure is fast, simple, highly sensitive and solvent free. SPME-GC-MS was also employed for the quantitative determination of triazines in the soil leachate, since the method showed good recovery yield. Detection limits were always better than 1 ng ml(-1). The method was tested on a contaminated landfill top soil. Prometryn and ametryn were identified through their MS spectra and then quantified. Terbuthylazine was used to assess recovery. Results compared well with those obtained by solvent extraction followed by HPLC-UV detection.     

Trace-level determination of triazines and several degradation products in environmental waters by disk solid-phase extraction and micellar electrokinetic chromatography

An analytical method combining disk solid-phase extraction with micellar electrokinetic chromatography has been developed for the determination of atrazine, simazine, hydroxyatrazine, deisopropylatrazine, deethylatrazine, propazine and prometryn in water samples. The influence of the buffer and sodium dodecyl sulfate (SDS) concentration, pH and organic modifier on the separation has been studied. Baseline separation of the seven triazines was achieved under the following conditions: 10 mM borate buffer, 60 mM SDS, 20% methanol and pH 9.2. C18-bonded silica and poly(styrene-divinylbenzene) (PS-DVB) disks were evaluated for solid-phase extraction of the selected pesticides (11 of water sample). Using two PS-DVB disks, quantitative recoveries were obtained for all pesticides tested. The method was successfully applied for the determination of the seven triazines in drinking and well water at the 0.1 microg l(-1) and 0.5 microg l(-1) concentration levels, respectively. The detection limits for these analytes using the proposed analytical method were within the 0.02-0.06 microg l(-1) range in drinking water and the 0.06-0.30 microg l(-1) range in well water.     

Selective extraction of triazine herbicides from food samples based on a combination of a liquid membrane and molecularly imprinted polymers

A selective extraction technique based on the combination of liquid membrane (microporous membrane liquid–liquid extraction) and molecularly imprinted polymers (MIP) was applied to triazines herbicides in food samples. Simazine, atrazine and propazine were extracted from aqueous food samples through the hydrophobic porous membrane that was impregnated with toluene, which also formed part of the acceptor phase. In the acceptor phase, the compounds were re-extracted onto MIP particles. The extraction technique was optimised for the amount of molecularly imprinted polymers particles in the organic acceptor phase, extraction time, and type of organic acceptor solvent and desorption solvent. An extraction time of 90 min and 50 mg of MIP were found to be optimum parameters. Toluene as the acceptor phase was found to give higher triazines binding onto MIP particles compared to hexane and combinations of diethyl ether and hexane. 90% methanol in water was found to be the best desorption solvent compared to acetonitrile, methanol and water. The selectivity of the technique was demonstrated by extracting spiked lettuce and apple extracts where clean chromatograms were obtained compared to liquid membrane extraction alone or to the microporous membrane liquid–liquid extraction – non-imprinted polymer combination. The MIP showed a certain degree of group specificity and the extraction efficiency in lettuce extract was 79% (0.72) for simazine, 98% (1.55) for atrazine and 86% (3.08) for propazine.     

Evaluation of a new method for chemical coating of aluminum wire with molecularly imprinted polymer layer. Application for the fabrication of triazines selective solid-phase microextraction fiber

A new solid-phase microextraction (SPME) fiber is fabricated through ultra violet irradiation polymerization of ametryn-molecularly imprinted polymer on the surface of anodized-silylated aluminum wire. The prepared fiber is durable with very good chemical and thermal stability which can be coupled to GC and GC/MS. The effective parameters on the fabrication and application procedures such as spraying mode, ultra violet irradiation (polymerization) time, number of sprayings and polymerizations, pH and ionic strength of sample and extraction time were optimized. This fiber shows high selectivity with great extraction capacity toward triazines. SPME and GC analysis of ametryn, prometryn, terbutryn, atrazine, simazine, propazine and cyanazine using the fabricated fiber result in the detection limits of 9, 32, 27, 43, 51, 74 and 85 ng mL⁻¹, respectively. The reliability of the prepared fiber in real samples has been investigated and proved by using spiked tap water, rice, maize and onion samples.     

Determination of triazine herbicides in fruits and vegetables using dispersive solid-phase extraction coupled with LC-MS

A simple, rapid, and sensitive liquid chromatography-mass spectrometry (LC-MS) method was successfully developed for the determination of three chloro-s-triazine herbicides, viz. atrazine, simazine, and propazine, two thiomethyl-s-triazine ones, viz. ametryn and prometryn, and prometon in fruits and vegetables. The instrumental parameters affecting LC separation and MS detection were investigated and the best conditions were selected. Samples were extracted and purified by dispersive solid-phase extraction (dispersive-SPE) with a primary-secondary amine sorbent. Three typical representative samples (luffa, broad bean, and grape) were selected to investigate the effect of different matrices on pesticide recoveries and assay precision after spiking at 0.05 mg/kg. Matrix composition did not interfere significantly with the determination of these pesticides. The recoveries were, with a few exceptions, in the range of 80-110% with relative standard deviations less than 10% (n = 5). In addition, this method was also applied to 21 different kinds of agriculture products collected from the local market, and two of the six triazines could be detected and quantified.     

A simple method for simultaneous determination of nine triazines in drinking water

A simple, effective, and economic method for determination of nine triazines (ametryn, atrazine, cyanazine, prometryn, propazine, simazine, simetryn, terbuthylazine, and terbutryn) in drinking water based on solid-phase extraction (SPE) followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was developed. A specialized solid phase (Oasis HLB) was used, and the parameters that may affect the efficiency of SPE were optimized. The limits of detection (ranged from 0.010 to 0.023 µg L^?1) were satisfactory and allow the determination of triazines at the levels required by European Union legislation. Repeatability (2.4–7.6%) and intermediate precision (0.9–11.0%) calculated at 0.1 µg L^?1 (legislation level) were adequate. The accuracy calculated as the average recovery of spiked tap and mineral waters was higher than 86% for all compounds. The developed method also could be used for undergraduate laboratory experiments because it acquaints students with solution preparation, solid phase extraction procedure, and HPLC-DAD technique.     

A nanoparticle-based solid-phase extraction method for liquid chromatography-electrospray ionization-tandem mass spectrometric analysis

A solid-phase extraction (SPE) procedure with the use of superparamagnetic Fe(3)O(4) nanoparticles as extracting agent was developed for HPLC-ESI-MS/MS analysis. Four most heavily used triazine pesticides (herbicides) were taken as the test compounds. The NPs showed an excellent capability to retain the compounds tested, and a quantitative extraction was achieved within 10min under the testing conditions, i.e. 100 microL NP solution was added to 400 mL sample in a beaker with stirring. After extraction, the superparamagnetic NPs were easily collected by using an external magnet. Very importantly, analytes retained on the Fe(3)O(4) NPs could be quantitatively recovered by dissolving the NPs with an HCl solution, allowing subsequent HPLC-ESI-MS/MS quantification. A capillary HPLC-ESI-MS/MS method with the present NP-based SPE procedure was developed for the determination of triazines including atrazine, prometryn, terbutryn, and propazine. Atrazine-d(5) was used as internal standard. The method had an LOD of 10 pg/mL atrazine, and a linear calibration curve over a range from 30 pg to 50.0 ng/mL. Simultaneous determination of the four triazine pesticides in water samples taken from local lakes was demonstrated.     

Preparation and Characterization of Prometryn Molecularly Imprinted Solid‐Phase Microextraction Fibers

Abstract

A novel reproducible solid‐phase microextraction (SPME) coating was prepared on the surface of silanized silica fibers by molecularly imprinted polymerization using prometryn as template molecule. The structure and extraction performance of molecularly imprinted polymer (MIP) coating was studied with the scanning electron microscope and high performance liquid chromatography (HPLC). Specific selectivity was found with the prometryn MIP‐coated fiber to prometry and its structural analogues such as atrazine, simetryn, terbutylazin, ametryn, propazine and terbutryn. In contrast, these triazines could not be selectively extracted by the non‐imprinted polymer fiber or commercial polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), polyacrylate (PA) fibers.     

Determination of pesticides in surface and ground waters by liquid chromatography-electrospray-tandem mass spectrometry

The sensitive multiresidual analytical method for simultaneous analysis of 14 most commonly used agricultural pesticides in Serbia was developed and optimized. The selected insecticides, fungicides and herbicides belong to seven chemical classes (organophosphates, neonicotinoids, carbamates, diacylhydrazines, benzimidazoles, triazines and phenylureas). The method was based on solid-phase extraction followed by liquid chromatography-tandem mass spectrometry. The following parameters that may affect the SPE procedure efficiency were optimized: the sorbent type in combination with different elution solvents, the sample pH and the sample volume. For each pesticide, MSⁿ analysis was performed and distinctive ions and transitions were selected for identification and quantification, as well as for confirmation purposes. External matrix-matched calibration method was used to eliminate variable matrix effect and ensure precise quantification. Good recoveries (72-129%), and low limits of detection (0.4-5.5 ng L⁻¹) and quantification (1.1-18.2 ng L⁻¹) were achieved for all selected pesticides. The developed and optimized method was successfully applied in the analysis of several river waters, as well as ground waters in Serbia, influenced by agriculture. The most frequently detected pesticide was carbendazim. Dimethoate, carbofuran and propazine were also found in the investigated samples.     

Selective Preconcentration of Mezlocillin from Eggs by Molecularly Imprinted Polymers on Silica

Surface molecularly imprinted polymers for mezlocillin were used for the selective solid-phase extraction of mezlocillin from eggs. The molecularly imprinted polymers were prepared using mezlocillin as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, silica particle as the support and were characterized by infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The adsorption properties of polymers were investigated in detail. The obtained polymers provided high imprinting efficiency to mezlocillin with an imprinting factor of 3.72 and were used as selective sorbents for mezlocillin. Molecularly imprinted solid-phase extraction followed by high-performance liquid chromatography was used for the determination of mezlocillin in eggs and the conditions were evaluated. The average recovery of mezlocillin in fortified eggs was between 69.8 and 82.3% with a relative standard deviation less than 6.9%. The results demonstrate the application of molecularly imprinted polymers for the extraction of mezlocillin from biological samples.     

Development of novel molecularly imprinted solid-phase microextraction fibers and their application for the determination of antibiotic drugs in biological samples by SPME-LC/MS(n)

Novel molecularly imprinted polymer (MIP)-coated fibers for solid-phase microextraction (SPME) fibers were prepared by using linezolid as the template molecule. The characteristics and application of these fibers were investigated. The polypyrrole, polythiophene, and poly(3-methylthiophene) coatings were prepared in the electrochemical polymerization way. The molecularly imprinted SPME coatings display a high selectivity toward linezolid. Molecularly imprinted coatings showed a stable and reproducible response without any influence of interferents commonly existing in biological samples. High-performance liquid chromatography with spectroscopic UV and mass spectrometry (MS) detectors were used for the determination of selected antibiotic drugs (linezolid, daptomycin, amoxicillin). The isolation and preconcentration of selected antibiotic drugs from new types of biological samples (acellular and protein-free simulated body fluid) and human plasma samples were performed. The SPME MIP-coated fibers are suitable for the selective extraction of antibiotic drugs in biological samples.     

Simultaneous Determination of Four Sudan Dyes in Egg Yolks by Molecularly Imprinted SPE Coupled with LC-UV Detection

A highly selective molecularly imprinted solid-phase extraction (MISPE) combined with liquid chromatography-ultraviolet detection was developed for the simultaneous isolation and determination of four Sudan dyes (I, II, III and IV) in egg-yolk products. The imprinted microspheres synthesized by suspension polymerization using phenylamine?Cnaphthol as mimic template show high selectivity and affinity to the four kinds of Sudan dyes and were successfully applied as selective sorbents of solid-phase extraction for the simultaneous determination of the four Sudans from egg-yolk samples. Good linearity was obtained in a range of 0.062?C10 ??g g^?1 and the average recoveries of the four Sudans at three spiked levels ranged from 94.1 to 102.5% with the relative standard deviations less than 5.8%. The developed extraction protocol eliminated the effect of template leakage on quantitative analysis and could be applied for the determination of Sudans in complicated food samples.     

The application of pseudo template molecularly imprinted polymer to the solid-phase extraction of cyromazine and its metabolic melamine from egg and milk

The combination of molecularly imprinted polymer with high performance liquid chromatography has been developed to determine cyromazine and its metabolic melamine in some samples. However, the potential risk of template leakage used in molecularly imprinted polymer is a major disadvantage. To solve this problem, 2-(4,6-diamino-1,3,5-triazin-2-ylamino) ethanethiol disulfide, a molecule that shares the similar imprinting sites with cyromazine and melamine, was selected as pseudo template to prepare molecularly imprinted polymer. Methacrylic acid, ethylene glycol dimethyl acrylate and toluene were selected as functional monomer, crosslinker and porogen, respectively. The molecular recognition property and binding capability of cyromazine and melamine were evaluated by adsorption test and Scatchard analysis. The results showed that the molecularly imprinted polymer based on pseudo template had more excellent affinity and selectivity for cyromazine and melamine. The resulting molecularly imprinted polymer was used as a solid-phase extraction material to enrich cyromazine and melamine in egg and milk samples for high performance liquid chromatography analysis. The solid-phase extraction process was carefully optimized. It was found that when different concentration of cyromazine and melamine standards were spiked into samples, satisfactory recovery rate of cyromazine and melamine were obtained as 85.6-98.8% with relative standard deviation <5.5%.     

Synthesis and characterization of molecularly imprinted polymers for selective solid-phase extraction of pseudoephedrine

Molecular imprinted solid-phase extraction (MISPE) is a well known technique for the selective extraction and pre-concentration of analytes, are present at low levels in chemically complex materials. Herein, water-soluble, molecularly imprinted polymers (MIP) were prepared for solid-phase extraction of pseudoephedrine hydrochloride (PSE), which was monitored at 256 nm by the UV spectroscopy. MISPE conditions were optimized to allow the selective and determination of PSE in aqueous samples and composite materials, such as biological fluids and human urine. MIP was prepared by precipitation polymerization method, using methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a cross-linking agent in either acetonitrile or chloroform. The results suggest that the obtained MISPE exhibits high affinity for PSE, and the imprinted polymer demonstrates much higher efficiency than a non-imprinted polymer (NIP). The imprinting-induced extraction was confirmed by the determination of recovery values for NIP (4%) and MIP (80%) polymers, respectively. The binding capacity of the MIP for PSE was found of 47.6 mg g⁻¹.     

Room temperature ionic liquid-mediated molecularly imprinted polymer monolith for the selective recognition of quinolones in pork samples

A novel molecularly imprinted polymer monolith was prepared by the room temperature ionic liquid-mediated in situ molecular imprinting technique, using norfloxacin (NOR) as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker. The optimal synthesis conditions and recognition properties of NOR-imprinted monolithic column were investigated. The results indicated that the imprinted monoliths exhibited good ability of selective recognition against the template and its structural analog. Using the fabricated material as solid-phase extraction sorbent, a sample pre-treatment procedure of molecularly imprinted solid-phase extraction coupling with HPLC was developed for determination of trace quinolone residues in animal tissues samples. The recoveries ranging from 78.16 to 93.50% for eight quinolones antibiotics such as marbofloxacin, NOR, ciprofloxacin, danofloxacin, difloxacin, oxolinic acid, flumequine and enrofloxacin were obtained.     

The extraction performance of methacrylic acid-trimethylolpropanetrimethacrylate solid-phase microextraction fibers in aqueous solutions

The extraction performance of solid-phase microextraction fibers, based on methacrylic acid-trimethylolpropanetrimethacrylate (MAA/TRIM) copolymers, was investigated in aqueous solutions using triazines as target analytes and 2-bromobiphenyl as a reference compound. The results revealed that the combination of electrostatic forces and hydrophobicity was the primary interaction between the MAA/TRIM coating and the triazines. To improve the selectivity of the MAA/TRIM-coated fiber for the triazines, several experimental parameters including pH of the sample solution, washing step, organic modifier, and salt concentration were optimized so as to amplify electrostatic interaction and suppress the hydrophobic effect. To evaluate the practicability of the proposed method, samples with complex matrixes, including corn extract and sewage sludge, were extracted with a MAA/TRIM-coated fiber under the optimized conditions chosen. The results showed that the extraction efficiency for target analytes was not enhanced, but the matrix effect of the interfering compounds in the samples was effectively restrained and thus the selectivity was obviously improved.