Abstract
Analytical method for the residues of strobilurins azoxystrobin and pyraclostrobin in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) cou-pled to gas chromatography with micro-electron capture detector. The effect of pH values and fiber coatings were studied. The SPME fiber coating selected was 100 μm PDMS. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged within the 100% - 106% range for azoxystrobin, and 96% - 106% range for pyraclostrobin; and detection and quantification limits were 2.0 and 6.0 μg/kg for azoxystrobin, and 26.0 and 86.0 μg/kg for py-raclostrobin, respectively. Statistical parameters indicated the occurrence of matrix effect; con-sequently calibration was performed on spiked samples. Degradation of azoxystrobin and pyra-clostrobin was studied in blueberry fields located in Concordia, Argentina, with fruits from Emerald and Jewel varieties. The degradation of these fungicides in both blueberry varieties studied followed a first order rate kinetics, and the half-life for azoxystrobin was 11.6 and 17.8 days for Emerald and Jewel cultivars; and for pyraclostrobin was 5.5 and 8.0 days, respectively.
Highlights
Azoxystrobin [methyl (2E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate—C22H17N3O5] and pyraclostrobin [methyl 2-[1-(4-chlorophenyl)pyrazol-3-yloxymethyl]-N-methoxycarbanilate—C19H18CIN3O4] are two of the most important fungicides used in blueberry fields (Figure 1(a) and Figure 1(b))
The extraction of azoxystrobin and pyraclostrobin was performed with PDMS, CWX-DVB and PA fiber coatings at different pH values (5.0 – 7.0 – 9.0) in triplicates with 15 minutes of extraction time and 2000 rpm
The results showed a good linearity with regression coefficient of 0.9965 and 0.9990 for azoxystrobin and pyraclostrobin, respectively
Summary
Azoxystrobin [methyl (2E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate—C22H17N3O5] and pyraclostrobin [methyl 2-[1-(4-chlorophenyl)pyrazol-3-yloxymethyl]-N-methoxycarbanilate—C19H18CIN3O4] are two of the most important fungicides used in blueberry fields (Figure 1(a) and Figure 1(b)). They have been determinated in different products by gas chromatography [1] or gas chromatography with mass spectrometry [2]-[9] or by liquid chromatography—mass spectrometry [10]-[13]. Contamination by different moulds can occur during pre-harvesting, harvesting and blueberry processing [14]-[19] To avoid this situation, the application of fungicides, as azoxystrobin and pyraclostrobin, is a common practice in the field. The current EU MRLs are 5.0 mg/kg for azoxystrobin and 3.0 mg/kg for pyraclostrobin
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