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ABSTRACT: The chemical control of crops by organophosphate insecticide treatment is usually limited because the insecticides do not maintain their efficiency for long periods for several reasons, including environmental conditions or rapid degradation of the active ingredient. Chlorpyrifos is an organophosphate insecticide used worldwide to control a variety of soil insects and arthropods in a wide range of crops. It is easily soluble in organic solvents but shows poor water solubility. The inclusion of chrorpyrifos in cyclodextrins (CDs) improves its water solubility, bioavailability, and insecticidal activity and helps prevent overdosing, leading to more cost-effective and more environmentally friendly agricultural practices. Solubility studies of chlorpyrifos in the presence of different types of CDs show G2-beta-CDs to be the most effective CDs in the complexation process, giving 1:2 complexes, with complexation constant (Kc) values of 12.34 +/- 3.1 M(-1) for K1 and 3895 +/- 183 M(-1) for K2. These complexation constant values were corroborated by applying a fluorimetric method.
Journal of Agricultural and Food Chemistry 10/2008; 56(17):8081-5. · 2.82 Impact Factor
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ABSTRACT: A comparative study of enzymatic and non-enzymatic labels combined with luminescence detection, developed for immunosensing of pesticide residues (carbaryl, 1-naphthol, irgarol 1051) in organic media, is presented. Peroxidase and alkaline phosphatase enzymes with fluorogenic (3-p-hydroxyphenylpropanoic acid) and luminogenic (AMPPD derivative) substrates, respectively, were assessed as enzymatic markers. As an alternative, terbium(III) chelate, with time-resolved fluorescence detection, was evaluated as a non-enzymatic label. The best sensitivity was achieved by use of alkaline phosphatase in an immunocomplex capture assay format (I (50) values 0.06, 0.27, and 7.45 microg L(-1) in buffer, 1:1 methanol-buffer, and methanol, respectively). Results were also good (I (50) 1.00 and 6.30 microg L(-1) for water and aqueous-organic mixture, respectively) for Tb(III) chelate in an immobilized conjugate assay format. Use of alkaline phosphatase label to measure carbaryl (100 ng L(-1)) in different spiked river water samples, after solid-phase extraction and analyte elution with an ethyl acetate-methanol mixture, resulted in recoveries ranging from 81 to 98%, with acceptable precision (CV 4-14%, n=4).
Analytical and Bioanalytical Chemistry 05/2006; 384(7-8):1540-7. · 3.78 Impact Factor
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ABSTRACT: Immunosensor systems have been developed for the rapid determination of 1-naphthol. In this work, the comparison of performance of immunosensors working in aqueous and organic media was done. Direct, indirect and capture formats were studied. Immunoreagents were immobilized on controlled pore glass (CPG), hidroxysuccinimide agarose gel or on azlactone Protein A/G supports. The Protein A/G-based sensor showed the best performance. In aqueous media, a LOD of 16.2 microg l(-1) and a DR of 33.7-586.6 microg l(-1) were achieved employing Tween 20 at a concentration ranging from 0.01 to 0.05% v/v. Maximum sensitivity was reached with 0.025% of surfactant. Binary mixtures of methanol or acetonitrile with aqueous buffer and ternary mixtures of methanol/isopropanol or ethyl acetate/methanol with the same buffer were studied as organic media. The mixture 50% MeOH-50% 20 mM sodium phosphate, pH 8, with 0.05% (v/v) Tween 20 resulted to be the best. A detection limit of 12.0 microg l(-1) and a dynamic range of 53.6-17,756.0 microg l(-1) were reached. The recycling of Protein A/G-based sensor working in this media was about 300 assays. Preconcentration factors around 250 were achieved using methanol as extracting solvent. It has been demonstrated that the technique can be successful in carrying out the analysis of low solubility in water analytes, such as 1-naphthol. The sensors developed can use higher concentrations of organic solvent (up to 50% methanol) compared to ELISA. On the other hand, the advantage of preconcentration can also be taken for the use of the same procedure as recommended for standard sample treatments.
Biosensors and Bioelectronics 07/2000; 15(3-4):99-106. · 5.60 Impact Factor
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ABSTRACT: The compatibility between organic solvents and immunoreagents was studied for the development of immunosensors for pesticides. On the basis on heterogeneous competitive enzyme formats, three assay types were used: immobilized antibodies (direct format), immobilized hapten conjugates (indirect format), and capture format based on immobilized protein A/G. In all cases, peroxidase enzyme label and fluorometric detection were employed. Initial findings were developed in batch working with the immunoreagents in different solvent systems (pure and mixed) to retrieve basic information about their performances. Monoclonal and polyclonal antibodies for carbaryl and 1-naphthol were used to develop sensors in different organic solvent mixtures. Polyclonal antibodies showed better sensitivity than monoclonal ones in comparable conditions. Sensitivity was better in the more polar solvents, methanol being the best. Comparison with an aqueous immunosensor showed lower sensitivity but better selectivity.
Analytical Chemistry 10/1999; 71(17):3862-72. · 5.86 Impact Factor
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ABSTRACT: The development of an immunosensor for analysis of the antifouling agent Irgarol 1051 (2-methylthio-4-tert-butylamin-6-cyclopropylamin-s-triazine) is described. The immunosensor is based on a heterogeneous competitive enzyme immunoassay and uses binder azlactone support with immobilized protein A/G. The flow-through immunosensor is completely automated and is able to carry out a whole analysis cycle in about 23 min. Competitive calibration curves have an /50 value of 0.053 μg/L (0.21 nM), with a limit of detection of 0.010 μg/L and a quantification dynamic range from 0.019 to 0.158 μg/L. The protein A/G support can be used for more than 600 assay cycles without less of sensor performance. The sensor is prone to some interferences from tert- butyl-containing s-triazine compounds, such as terbutryn and terbumeton, but little inteference is shown for other s-triazine compounds, e.g., atrazine or simazine. The developed sensor is applied to the determination of trace levels of Irgarol 1051 in water samples such as Mediterranean marina and beach seawater, estuarine river water, and lake water, without any sample pretreatment other than adjusting the pH and ionic strength of samples to those of standards. Good correlation is achieved between the immunosensor results and ELISA or HPLC analyses. The development of an immunosensor for analysis of the antifouling agent Irgarol 1051 (2-methylthio-4-tert-butylamin-6-cyclopropylamin-s-triazine) is described. The immunosensor is based on a heterogeneous competitive enzyme immunoassay and uses binder azlactone support with immobilized protein A/G. The flow-through immunosensor is completely automated and is able to carry out a whole analysis cycle in about 23 min. Competitive calibration curves have an I50 value of 0.053 μg/L (0.21 nM), with a limit of detection of 0.010 μg/L and a quantification dynamic range from 0.019 to 0.158 μg/L. The protein A/G support can be used for more than 600 assay cycles without loss of sensor performance. The sensor is prone to some interferences from tert-butyl-containing s-triazine compounds, such as terbutryn and terbumeton, but little interference is shown for other s-triazine compounds, e.g., atrazine or simazine. The developed sensor is applied to the determination of trace levels of Irgarol 1051 in water samples such as Mediterranean marina and beach seawater, estuarine river water, and lake water, without any sample pretreatment other than adjusting the pH and ionic strength of samples to those of standards. Good correlation is achieved between the immunosensor results and ELISA or HPLC analyses.
Environmental Science and Technology. 01/1998; 32(21):3442-3447.
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ABSTRACT: Immunosensor systems have been developed for the rapid determination of l-naphthol. In this work, the comparison of performance of immunosensors working in aqueous and organic media was done. Direct, indirect and capture formats were studied. Immunoreagents were immobilized on controlled pore glass (CPG), hidroxysuccinimide agarose gel or on azlactone Protein A/G supports. The Protein A/G-based sensor showed the best performance. In aqueous media, a LOD of 16.2 μg l−1 and a DR of 33.7–586.6 μg l−1 were achieved employing Tween 20 at a concentration ranging from 0.01 to 0.05% v/v. Maximum sensitivity was reached with 0.025% of surfactant. Binary mixtures of methanol or acetonitrile with aqueous buffer and ternary mixtures of methanol/isopropanol or ethyl acetate/methanol with the same buffer were studied as organic media. The mixture 50% MeOH-50% 20 mM sodium phosphate, pH 8, with 0.05% (v/v) Tween 20 resulted to be the best. A detection limit of 12.0 μg l−1 and a dynamic range of 53.6–17 756.0 μg l−1 were reached. The recycling of Protein A/G-based sensor working in this media was about 300 assays. Preconcentration factors around 250 were achieved using methanol as extracting solvent. It has been demonstrated that the technique can be successful in carrying out the analysis of low solubility in water analytes, such as l-naphthol. The sensors developed can use higher concentrations of organic solvent (up to 50% methanol) compared to ELISA. On the other hand, the advantage of preconcentration can also be taken for the use of the same procedure as recommended for standard sample treatments.
Biosensors and Bioelectronics.
