Cloud point method applied to the extraction and preconcentration of thiabendazole pesticide from whole grape juice samples and amperometric detection by HPLC.

A cloud point method was developed and applied for the first time to extract and preconcentrate thiabendazole (TBZ) from commercial whole grape juice samples, with determination by high performance liquid chromatography coupled to electrochemical detection (HPLC/EC), using a cathodically pretreated boron-doped diamond electrode (BDD). The best conditions for extraction and preconcentration of TBZ by cloud point extraction (CPE) were performed at pH 6.0, by adding 1 mL of the surfactant Tergitol TMN-6 at 10% (mass-to-mass ratio), without heating (at 27 °C) and ultrasonic stirring time of (20 kHz) for 60 min. The HPLC/EC determination was duly validated in a C8 column, in mobile phase with a 69 : 31 ratio (V/V) of phosphate buffer (pH 7.0):ACN, at a flow rate of 1.2 mL min-1 and electrochemical detection with BDD electrode by applying 1.40 V × Ag/AgCl (3.0 mol L-1). Under these conditions, the procedure showed a preconcentration factor (FC) of 21.7, and limits of detection (LOD) and quantification (LOQ) of 6.64 × 10-9 mol L-1 (or 1.33 µg L-1) and 1.66 × 10-8 mol L-1 (or 3.34 µg L-1), respectively. The method provided a percent recovery of 81% to 98%, with a coefficient of variation between 3% and 15%.

Development and application of SBA-15 assisted electromembrane extraction followed by corona discharge ion mobility spectrometry for the determination of Thiabendazole in fruit juice samples.

A new sample preparation method based on SBA-15 assisted electromembrane extraction coupled with corona discharge ion mobility spectrometer was developed for the determination of Thiabendazole as a model basic pesticide in fruit juice samples. The addition of SBA-15 in the supported liquid membrane in electromembrane extraction system not only can lead to enhancement of the effective surface area, but also introducing the negatively charged silanol groups into supported liquid membrane might improve migration of positively charged analytes toward the supported liquid membrane and finally into the acceptor solution. To investigate the effect of the presence of SBA-15 in the supported liquid membrane on the extraction efficiency, a comparative study was carried out between the conventional electromembrane extraction and SBA-15/electromembrane extraction methods. Under the optimized conditions, SBA-15/electromembrane extraction method showed higher extraction efficiencies in comparison with conventional electromembrane extraction method. SBA-15/electromembrane extraction method exhibited a low limit of detection (0.9 ng/mL), high preconcentration factor (167) and high recovery (83%). Finally, the applicability of SBA-15/electromembrane extraction method was studied by the extraction and determination of Thiabendazole as a model basic pesticide in fruit juice samples.

Molecularly imprinted polymer monolith containing magnetic nanoparticles for the stir-bar sorptive extraction of thiabendazole and carbendazim from orange samples.

In this work, a novel molecularly imprinted stir-bar was developed for the stir-bar sorptive extraction (SBSE) of thiabendazole (TBZ) and carbendazim (CBZ) from orange samples. Magnetic nanoparticles were surface modified with oleic acid and then encapsulated by a silica shell using a conventional sol-gel procedure. Subsequently, nanoparticles were functionalized with methacrylate functionalities by grafting onto the particles surface. Finally, the modified magnetic nanoparticles were entrapped in a polymer monolith synthetized by copolymerization with the imprinting polymerization mixture using a glass vial insert as a mold. Variables affecting the polymerization and rebinding conditions of target analytes were optimized. The uptake capacity for the template (TBZ) was evaluated as well as the cross-reactivity for the related compound CBZ by rebinding experiments. Finally, the proposed magnetic imprinted monolith was applied to the SBSE of TBZ and CBZ from orange sample extracts providing a remarkable clean-up ability. The calculated detection limit were 0.13 and 0.10 mg kg-1 for CBZ and TBZ respectively, low enough to satisfactory analysis of both compounds in orange samples according to current European Union regulations.

[Determination of carbendazim and thiabendazole in wine and beer by ultra high performance liquid chromatography-high resolution mass spectrometry coupled with dispersive micro solid-phase extraction].

A rapid method was established for the determination of carbendazim and thiabendazole in wine and beer by ultra high performance liquid chromatography-Q Orbitrap high resolution mass spectrometry and dispersive micro solid-phase extraction (DMSPE) based on a strong cation exchange adsorbent (PCX). For the pretreatment method, the amount of PCX, the volume percentage of acetonitrile, the volume percentage of ammonium hydroxide and the volume of eluent were optimized. The analytes were separated on a BEH C18 column (50 mm×2.1 mm, 1.7 µm) and detected using targeted single ion monitoring-data dependent tandem mass spectrometry (tSIM-ddMS2) scan mode. The method showed a good linearity within a certain concentration ranges with correlation coefficients R2 ≥ 0.9999. The detection limits of carbendazim and thiabendazole in wine and beer were 0.02 and 0.01 µg/L, and the quantification limits were 0.06 and 0.03 µg/L. The average recoveries of carbendazim and thiabendazole at the spiked levels of 0.1, 1.0 and 100 µg/L were in the ranges of 95.6%-110.2% and 87.5%-102.8%, with intra-day precision (RSDr) ranges from 1.8%-5.2% and 1.3%-4.8%, and inter-day precision (RSDR) ranges from 4.3%-8.7% and 4.8%-9.4%. The method is rapid, simple and sensitive for the simultaneous determination of carbendazim and thiabendazole in wine and beer.

Hollow fiber membrane-protected molecularly imprinted microspheres for micro solid-phase extraction and clean-up of thiabendazole in citrus samples.

In the present work, molecularly imprinted polymer (MIP) microspheres were packed in polypropylene hollow fiber (HF) segments for the micro solid-phase extraction and clean-up of thiabendazole (TBZ) in citrus samples. Experimental parameters affecting TBZ extraction were carefully optimized. Hollow fiber membrane was able to protect MIP beads from solid matrix allowing the extraction and clean-up without the inclusion of further filtration and/or centrifugation steps. Under optimum experimental conditions, recoveries for TBZ at 0.83 mg kg-1 concentration level ranged from 5.1 to 6.1%, depending upon the sample analyzed (orange or lemon peel samples), with relative standard deviations (RSDs) lower than 4%. The limits of detection were 0.004 mg kg-1 in orange and 0.009 mg kg-1 in lemon, low enough for the determination of TBZ according to European Union legislation.

Molecularly imprinted magnetic nanoparticles for the micro solid-phase extraction of thiabendazole from citrus samples.

The preparation of molecularly imprinted core-shell magnetic nanoparticles and their subsequent use in the solid-phase extraction of thiabendazole from citrus sample extracts is described. Molecularly imprinted core-shell magnetic nanoparticles were prepared by the precipitation copolymerization of the imprinting polymerization mixture on the surface of vinyl-modified silica magnetic nanoparticles and were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The obtained molecularly imprinted core-shell magnetic nanoparticles exhibited a high selectivity for thiabendazole and were easily collected and separated by an external magnetic field without additional centrifugation or filtration steps. Under optimum conditions, a magnetic molecularly imprinted solid-phase extraction method was developed allowing the extraction of thiabendazole from citrus sample extracts and final determination by high-performance liquid chromatography with fluorescence detection. The detection limit was 0.2 mg/kg, far lower than the maximum residue limit established within the European Union for thiabendazole in citrus samples.

Simultaneous Determination of Seven Kinds of Fungicides in Citrus Fruits by Gas Chromatograghy/Mass Spectrometry.

A simple and accurate procedure was developed for the determination of seven fungicides, azoxystrobin (AZO), diphenyl (DP), fludioxonil (FLUDI), imazalil (IMZ), o-phenylphenol (OPP), pyrimethanil (PYRI) and thiabendazole (TBZ), in citrus fruits. The citrus fruit sample was extracted with acetonitrile and cleaned up with a graphite carbon/aminopropyl silanized silica gel solid-phase extraction cartridge using acetonitrile-toluene (3 : 1, v/v) as the eluent. Triphenylene was used as an internal standard (I.S.) at the concentration of 0.5 µg/mL. The sample solution was subjected to GC-MS utilizing the matrix-matched standard solution method. The recoveries of AZO, FLUDI, IMZ, OPP, PYRI and TBZ spiked in domestic citrus fruits (Satsuma mandarin) at the level of 0.01-10.0 µg/g were 72.8-104% and the limits of quantification were 0.01 µg/g. The recoveries of DP spiked in domestic citrus fruits at the level of 0.01-70.0 µg/g were 70.8-80.4% and the limit of quantification was 0.01 µg/g. The proposed method was applied to the determination of fungicides in citrus fruits purchased in various markets.

Development and validation of a method to determine thiabendazole and o-phenylphenol in wastewater using micellar liquid chromatography-fluorescence detection.

A micellar liquid chromatographic method to determine thiabendazole (TBZ) and o-phenylphenol in wastewater is described here. The sample was directly injected without any additional treatment other filtration. The pesticides were resolved in <11 min, using a mobile phase of 0.10 M SDS-6% 1-pentanol buffered at pH 3 running through a C18 column at 1 mL/min. The detection was performed by fluorescence at 305/360 and 245/345 nm excitation/emission wavelengths for TBZ and o-phenylphenol, respectively. The method was validated following the directives of the Validation and Peer Review of U.S. Environmental Protection Agency Chemical Methods of Analysis guidelines in terms of selectivity, quantitation range (0.01-0.02 to 2 mg/L), detection limit (0.005-0.008 mg/L), trueness (92.1-104.2%), precision (<13.9%), robustness (<6.6%), and stability under storage conditions. The procedure was applied to the screening of TBZ and o-phenylphenol in wastewater samples from citrus packing plants, agricultural gutters, urban sewage, as well as in influent and effluent wastewater treatment plants.

Recovery and quantitative detection of thiabendazole on apples using a surface swab capture method followed by surface-enhanced Raman spectroscopy.

We developed a rapid and simple method which combines a surface swab capture method and surface-enhanced Raman spectroscopy for recovery and quantitative detection of thiabendazole on apple surfaces. The whole apple surface was swabbed and the swab was vortexed in methanol releasing the pesticide. Silver dendrites were then added to bind the pesticide and used for enhancing the Raman signals. The recovery of the surface swab method was calculated to be 59.4-76.6% for intentionally contaminated apples at different levels (0.1, 0.3, 3, and 5 ppm, µg/g per weight). After considering the releasing factor (66.6%) from the swab, the final accuracy of the swab-SERS method was calculated to be between 89.2% and 115.4%. This swab-SERS method is simple, sensitive, rapid (∼10 min), and quantitative enough for QA/QC in plant procedure. This can be extended to detect other pesticides on raw agricultural produce like pears, carrots, and melons etc.

Novel metal-ion-mediated, complex-imprinted solid-phase microextraction fiber for the selective recognition of thiabendazole in citrus and soil samples.

A novel metal-ion-mediated complex-imprinted-polymer-coated solid-phase microextraction (SPME) fiber used to specifically recognize thiabendazole (TBZ) in citrus and soil samples was developed. The complex-imprinted polymer was introduced as a novel SPME coating using a "complex template" constructed with Cu(II) ions and TBZ. The recognition and enrichment properties of the coating in water were significantly improved based on the metal ion coordination interaction rather than relying on hydrogen bonding interactions that are commonly applied for the molecularly imprinting technique. Several parameters controlling the extraction performance of the complex-imprinted-polymer-coated fiber were investigated including extraction solvent, pH value, extraction time, metal ion species, etc. Furthermore, SPME coupled with HPLC was developed for detection of TBZ, and the methods resulted in good linearity in the range of 10.0-150.0 ng/mL with a detection limit of 2.4 ng/mL. The proposed method was applied to the analysis of TBZ in spiked soil, orange, and lemon with recoveries of 80.0-86.9% and RSDs of 2.0-8.1%. This research provides an example to prepare a desirable water-compatible and specifically selective SPME coating to extract target molecules from aqueous samples by introducing metal ions as the mediator.

Molecularly imprinted stir bars for selective extraction of thiabendazole in citrus samples.

Stir-bar sorptive extraction is based on the partitioning of target analytes between the sample (mostly aqueous-based liquid samples) and a stationary phase-coated magnetic stir bar. Until now, only PDMS-coated stir bars are commercially available, restricting the range of applications to the non-selective extraction of hydrophobic compounds due to the apolar character of PDMS. In this work, a novel stir bar coated with molecularly imprinted polymer as selective extraction phase for sorptive extraction of thiabendazole (TBZ) was developed. Two different procedures, based on physical or chemical coating, were assessed for the preparation of molecularly imprinted stir bars. Under optimum conditions, recoveries achieved both in imprinted and non-imprinted polymer stir bars obtained by physical coating were very low, whereas TBZ was favourably retained by imprinted over non-imprinted polymer stir bars obtained by chemical coating and thus the latter approach was used in further studies. Different parameters affecting both stir-bars preparation (i.e. cross-linker, porogen, polymerization time) and the subsequent selective extraction of TBZ (i.e. washing, loading and elution solvents, extraction time) were properly optimized. The molecularly imprinted coated stir bars were applied to the extraction of TBZ from citrus samples (orange, lemon and citrus juices) allowing its final determination at concentrations levels according to current regulations.

Molecularly imprinted polymer grafted to porous polyethylene frits: a new selective solid-phase extraction format.

In this paper, a novel format for selective solid-phase extraction based on a molecularly imprinted polymer (MIP) is described. A small amount of MIP has been synthesized within the pores of commercial polyethylene (PE) frits and attached to its surface using benzophenone (BP), a photo-initiator capable to start the polymerisation from the surface of the support material. Key properties affecting the obtainment of a proper polymeric layer, such as polymerisation time and kind of cross-linker were optimised. The developed imprinted material has been applied as a selective sorbent for cleaning extracts of thiabendazole (TBZ), as model compound, from citrus samples. The use of different solvents for loading the analyte in the imprinted frits was investigated, as well as the binding capacity of the imprinted polymer. Imprinted frits showed good selectivity when loads were performed using toluene and a linear relationship was obtained for the target analyte up to 1000 ng of loaded analyte. Prepared composite material was applied to the SPE of TBZ in real samples extracts, showing an impressive clean-up ability. Calibrations showed good linearity in the concentration range of 0.05-5.00 µg g(-1), referred to the original solid sample, and the regression coefficients obtained were greater than 0.996. The calculated detection limit was 0.016 µg g(-1), low enough to satisfactory analysis of TBZ in real samples. RSDs at different spiking levels ranged below 15% in all the cases and imprinted frits were reusable without loss in their performance.

Synthesis of core-shell molecularly imprinted polymer microspheres by precipitation polymerization for the inline molecularly imprinted solid-phase extraction of thiabendazole from citrus fruits and orange juice samples.

In this work, the synthesis of molecularly imprinted polymer microspheres with narrow particle size distributions and core-shell morphology by a two-step precipitation polymerization procedure is described. Polydivinylbenzene (poly DVB-80) core particles were used as seed particles in the production of molecularly imprinted polymer shells by copolymerization of divinylbenzene-80 with methacrylic acid in the presence of thiabendazole (TBZ) and an appropriate porogen. Thereafter, polymer particles were packed into refillable stainless steel HPLC columns used in the development of an inline molecularly imprinted SPE method for the determination of TBZ in citrus fruits and orange juice samples. Under optimized chromatographic conditions, recoveries of TBZ within the range 81.1-106.4%, depending upon the sample, were obtained, with RSDs lower than 10%. This novel method permits the unequivocal determination of TBZ in the samples under study, according to the maximum residue levels allowed within Europe, in less than 20 min and without any need for a clean-up step in the analytical protocol.

A matrix solid-phase dispersion method for the extraction of seven pesticides from mango and papaya.

A simple and effective extraction method based on matrix solid-phase dispersion was developed to determine trichlorfon, pyrimethanil, methyl parathion, tetraconazole, thiabendazole, imazalil, and tebuconazole in papaya and mango using gas chromatography-mass spectrometry with selected ion monitoring. Different parameters of the method were evaluated, such as type of solid-phase (silica-gel, neutral alumina, and Florisil), the amount of solid-phase, and eluent [dichloromethane, ethyl acetate-dichloromethane (4:1, 1:4, 1:1, 2:3, v/v)]. The best results were obtained using 2.0 g of mango or papaya, 3.0 g of silica as dispersant sorbent, and ethyl acetate-dichloromethane (1:1, v/v) as eluting solvent. The method was validated using mango and papaya samples fortified with pesticides at different concentration levels (0.05, 0.10, and 1.0 mg/kg). Average recoveries (4 replicates) ranged from 80% to 146%, with relative standard deviations between 1.0% and 28%. Detection and quantification limits for mango and papaya ranged from 0.01 to 0.03 mg/kg and 0.05 to 0.10 mg/kg, respectively. The proposed method was applied to the analysis of these compounds in commercial fruit samples from a local market (Aracaju/SE, Brazil), and residues of the pesticides were not detected on the samples.

Determination of benzimidazolic fungicides in fruits and vegetables by supramolecular solvent-based microextraction/liquid chromatography/fluorescence detection.

A supramolecular solvent consisting of vesicles, made up of equimolecular amounts of decanoic acid (DeA) and tetrabutylammonium decanoate (Bu4NDe), dispersed in a continuous aqueous phase, is proposed for the extraction of benzimidazolic fungicides (BFs) from fruits and vegetables. Carbendazim (CB), thiabendazole (TB) and fuberidazole (FB) were extracted in a single step and no clean-up or concentration of extracts was needed. The high extraction efficiency obtained for BFs was a result of the different types of interactions provided by the supramolecular solvent (e.g. hydrophobic and hydrogen bonds) and the high number of solubilisation sites it contains. Besides simple and efficient, the proposed extraction approach was rapid, low-cost, environment friendly and it was implemented using conventional lab equipments. The target analytes were determined in the supramolecular extract by LC/fluorescence detection. They were separated in a Kromasil C18 (5 microm, 150 mm x 4.6 mm) column using isocratic elution [mobile phase: 60:40 (v/v) 50 mM phosphate buffer (pH 4)/methanol] and quantified at 286/320 nm (CB) and 300/350 nm (TB and FB) excitation/emission wavelengths, respectively. Quantitation limits provided by the supramolecular solvent-based microextraction (SUSME)/LC/fluorescence detection proposed method for the determination of CB, TB and FB in fruits and vegetables were 14.0, 1.3 and 0.03 microg kg(-1), respectively, values far below the current maximum residue levels (MRLs) established by the European Union, i.e. 100-2000 microg kg(-1) for CB, 50-5000 microg kg(-1) for TB and 50 microg kg(-1) for FB. The precision of the method, expressed as relative standard deviation, for inter-day measurements (n=13) was 3.3% for CB (50 microg kg(-1)), 3.5% for TB (10 microg kg(-1)) and 2.8% for FB (0.5 microg kg(-1)) and recoveries for fruits (oranges, tangerines, lemons, limes, grapefruits, apples, pears and bananas) and vegetables (potatoes and lettuces) fortified at the microg kg(-1) level were in the interval 93-102%.

Dispersive liquid-liquid microextraction combined with high performance liquid chromatography-fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples.

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1 mol L(-1) HCl. Then, the pH of the extract was adjusted to 7.0 with 2 mol L(-1) NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl(3)) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5-800 ng mL(-1) for water sample analysis, and 10-1000 ng g(-1) for soil samples, respectively. The correlation coefficients (r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5-1.0 ng mL(-1) for water samples, and 1.0-1.6 ng g(-1) for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% (n=5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20 ng mL(-1) were 84.0-94.0% and 86.0-92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100 ng g(-1) varied between 82.0 and 93.4%.

[Determination of benomyl, carbendazim and thiabendazole in apple juice concentrate using solid-phase extraction coupled with ion exchange chromatography].

A method was developed for the determination of benomyl, carbendazim and thiabendazole in apple juice concentrate by solid-phase extraction coupled with ion exchange chromatography (IEC). The sample was diluted with water, and then benomyl was degradated completely to carbendazim at 80 degrees C, and purified by an SCX solid-phase extraction column. Liquid chromatographic analysis was performed on the instrument of Agilent 1200 series equipped with a diode-array detector and autosampler. The column was LC-SCX (25 cm x 4.6 mm, 5 microm). The mobile phase was 0.1 mol/L KH2PO4 (pH 2.5)-acetonitrile (70:30, v/v) with a flow rate of 1.0 mL/min. The presented method showed good linear relationship with good precision and accuracy at the range of 0.02 - 2.0 mg/L for carbendazim and thiabendazole. The detection limits were 0. 004 mg/kg for carbendazim and thiabendazole. The method was characterized with acceptable sensitivity to meet the requirements for monitoring these pesticides in apple juice concentrate.

Determination of thiabendazole residues in meat by HPLC using ultraviolet and fluorometric detection.

An HPLC method is described for the residue analysis of thiabendazole in meat. The recovery varies from 62 to 75%. Thiabendazole is extracted from the tissue using 3 mol HCl, eluted from the Extrelut-20 column with dichloromethane and then injected onto a C18 column. The optimum conditions for detection are described using ultraviolet and fluorescence spectroscopy. The sensitivity is such that thiabendazole can be determined at a level of 5 micrograms/kg meat. The absolute detection limit with fluorometry is 100 pg.