pyrachlostrobin and acetonitrile

A new assay of micellar electrokinetic capillary chromatography with sweeping was developed to determine azoxystrobin, kresoxim-methyl and pyraclostrobin in fruits and vegetables. The key factors affecting resolution and peak height were studied and the optimum conditions were obtained for separation and enrichment. The running buffer consisted of 40 mM borate, 25 mM sodium dodecyl sulfate and 15% acetonitrile, and its pH was adjusted to 8.4. The sample was injected for 677 nL and the separation voltage was 25 kV. Under the optimum conditions, the enrichment factors of azoxystrobin, kresoxim-methyl and pyraclostrobin were 861, 550 and 403; the linear dynamic ranges were all 0.01-5.0 mg/L; the limits of detection were 0.002, 0.001 and 0.002 mg/kg; the recoveries of spiked samples were 85.1-98.5%, 87.5-97.0% and 89.1-99.1%, respectively. The assay can meet the requirement of maximum residue limits for these three strobilurin fungicides, and has been applied for determining their residues in fruits and vegetables.

Topics: Acetonitriles; Carbamates; Chromatography, Micellar Electrokinetic Capillary; Fruit; Fungicides, Industrial; Hydrogen-Ion Concentration; Limit of Detection; Methacrylates; Pesticide Residues; Phenylacetates; Pyrazoles; Pyrimidines; Reproducibility of Results; Strobilurins; Vegetables

Pyraclostrobin belongs to a new generation of fungicides widely used to preserve high valuable crops. In the present study, three monoclonal antibodies with different affinities to this modern strobilurin have been evaluated for their usefulness in the production of immunoaffinity columns suitable for the solid-phase extraction, concentration, and clean-up of residues from food commodities. Different immunosorbents were produced and characterized in terms of antibody immobilization efficiency, immunosorbent binding capacity, optimum elution conditions, and reusability. Covalent coupling of the antibodies to Sepharose-CNBr gel took place with high yield (over 90%), whereas the immunosorbent efficacy to retain the analyte (from 28 to 68%) was shown to depend on the amount and type of antibody immobilized on the support. As a matter of fact, columns prepared with the monoclonal antibody PYs5#14 were able to selectively bound up to 53 μg of pyraclostrobin per gram of beads. Acetonitrile solutions were preferred over methanolic ones for analyte elution, and some immunosorbents could be reused at least 4-6 times provided that the amount of pyraclostrobin and the volume of sample did not overload the column. Effectiveness of the selected immunoaffinity column was evidenced by the development of an extraction procedure for pyraclostrobin residues from fruit juices and further determination by high-performance liquid chromatography with UV detection. A concentration factor of 50 times was achieved with the developed immunoaffinity column, which eventually resulted in a limit of quantification of 0.01 mg L(-1). Finally, quantitative recoveries were obtained on apple juice and red grape must samples spiked with pyraclostrobin from 0.01 to 1 mg L(-1).

Topics: Acetonitriles; Antibodies, Monoclonal; Beverages; Carbamates; Chromatography, Affinity; Equipment Reuse; Fruit; Fungicides, Industrial; Immunosorbent Techniques; Malus; Pesticide Residues; Pyrazoles; Sensitivity and Specificity; Spectrophotometry, Ultraviolet; Strobilurins; Vitis