Detection of captan in strawberries


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MATRIX: Strawberries


RANGE OF DETECTION: 3.2 to 120 ppm

Captan RaPID AssayÒ Kit and Sample Diluent. Food Prep Kit. Reagents: acetone (pesticide grade). Equipment: homogenizer or blender with acetone resistant container cup, 50 mL polypropylene conical tubes, 13 x 100 mm glass test tubes, serological pipets, micropipette (50mL), vortex mixer, centrifuge (optional), scale or balance, nitrogen gas.

SAMPLE PREPARATION: Chop the strawberry sample to be analyzed coarsely by hand or in a food processor.

With homogenizer: Add 20 mL of acetone to 10 grams of chopped strawberry sample in 50 mL conical tube. Homogenize the sample thoroughly to disrupt fruit tissues. With blender: Weigh out an amount of chopped sample that provides a representative subsample of the strawberries to be analyzed. Add the weighed sample to a blender with an acetone resistant cup. Add a volume of acetone (in mL) equal to twice the weight (in grams) of the strawberries, e.g. 50 g strawberries plus 100 mL acetone. Blend the mixture thoroughly to disrupt fruit tissues. Transfer approximately 25 mL of the mixture to a 50 mL conical tube. Allow large particulates in the homogenate to settle to the bottom of the conical tube (at least five minutes). If strawberry solids do not settle easily, centrifuge gently. Transfer approximately 4 mL of the acetone extract (upper layer) to an Extract Cleanup Reagent Tube from the Food Prep Kit. Vortex the tube for 15 seconds. Using the scoop provided in the kit, add one scoopful of Salt Reagent to the tube. Cap the tube and vortex to mix thoroughly. Allow the aqueous and acetone phases to separate for about 5 minutes.

Carefully transfer 50 mL of the acetone phase (top layer) to a glass test tube and evaporate to dryness under nitrogen. Redissolve the residue in exactly 1 mL of the Sample Diluent. After the extract has been diluted with the Sample Diluent, the assay should proceed without interruption. Analyze the diluted extract as the 'sample' according to package insert of the RaPID Assay.

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