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A solid-phase microextraction (SPME) procedure followed by gas chromatography electron capture detection (GC/ECD) for the determination of triazole residues was developed. An experimental design with two steps was done. Firstly, a 2 6−2 fractional factorial design for screening several experimental variables (fiber-coating type, extraction temperature, extraction time, stirring rate, desorption temperature, and desorption time) was done. After, a twofactor central composite design for optimizing, the experimental conditions were carried out. The chosen experimental conditions were: fiber, PDMS/DVB; extraction time, 45 min; extraction temperature, 60°C; desorption time, 3 min; desorption temperature, 260°C, and stirring speed, 500 rpm. Using those conditions the limits of detection obtained for tetraconazole, myclobutanil, and diniconazole were in the order of few μg L −1 in grape and apple liquid extracts. Recoveries were from 93.6% to 112.1%. Relative standard deviation ranged from 1.2% to 11.6% (apple) and 6.7 to 18.0% (grape). The method was applied to five grape samples and 13 apple samples collected in Navarra, Rioja, and Basque Country. Quantification was performed by the standard addition method. Three standard additions by duplicate covering adequate range concentration were used. Myclobutanil was found in three apple samples (110-122 μg L −1 ) and diniconazole in one grape sample (9.4 μg L −1 ).

A screening method for determination of six triazole fungicides (diniconazole, fluquinconazole, flusilazole, myclobutanil, tebuconazole and tetraconazole) using the solid-phase microextraction (SPME) technique coupled to a high-performance liquid chromatography-diode array detector (HPLC-DAD) was developed. Experimental variables were chosen and their values were fixed according to an experimental design with the steps of screening (2 5À1 fractional factorial design) and optimization of the significant variables (central composite design). Using polydimethylsiloxane/divinylbenzene (PDMS/ DVB) fibers, the other experimental conditions were: extraction time, 90 min; extraction temperature, 60 C; NaCl addition, 180 g L À1 ; static desorption mode and desorption time, 2 min. The method showed good inter and intraday precision (RSD values less than 13.2%) and the limits of detection were from 1.5 to 5.9 mg L À1 in liquid extracts and from 0.08 to 0.3 mg kg À1 in solid products. The method was applied to grape and apple fruit samples previously sprayed with commercial products containing the analytes. Samples were taken from peel, pulp and juice following a pre-harvest interval of two weeks. Also, rain samples under the fruit trees were collected. Myclobutanil and tebuconazole were found in the peel and rain, but not in pulp and juice samples.

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