Detection of carbendazim in soil

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MATRIX: Soil

ANALYTE: Carbendazim, a metabolite of benomyl

RANGE OF DETECTION: 37.5 to 750 ppb

MATERIALS:
Benomyl/Carbendazim RaPID Assay kit and Sample Diluent Reagents: methanol (pesticide grade), sodium hydroxide (ACS grade), distilled or deionized water. Equipment: reciprocating shaker, plastic bottles (polypropylene or high density polyethylene, 50 or 60 mL) with plastic lined screw caps, filtration apparatus (funnel and filter paper or syringe/filter) or centrifuge, equipment/tools for grinding and mixing soil, serological pipets.

EXTRACTANT PREPARATION:
Prepare a 0.5N sodium hydroxide solution by dissolving 2 g NaOH pellets in 100 mL water. Prepare the soil extractant by mixing one part 0.5 N NaOH solunt iwoith 3 parts methanol. Sufficient quantity of extractant can be prepared in advance and stored for later use.

SAMPLE PREPARATION:
Allow frozen samples to thaw. Break up large (> 1 cm dia.) soil aggregates and mix sample thoroughly to uniformity with a mixer, mortar and pestle or by hand with a spatula or spoon. For moist samples, soil may be air dried at room temperature by spreading soil in a thin layer for up to 24 hours prior to mixing.

EXTRACTION PROCEDURE:
Useful results can be obtained with extraction times as short as five minutes, depending on the objective of the study, especially when large sample loads are present and when time and cost constraints are critical. The following protocol is recommended when assessing ppb levels while extracting most of the pesticide for analysis.

Add 30 mL of extractant (prepared above) to 10 g of soil in the plastic bottle. Position the sample bottle on its side and shake vigorously on reciprocating shaker at high speed (200 cycles/min.) for 30 minutes. Allow sample to sit 16 to 24 hours. Then shake sample vigorously again for 30 minutes. Allow soil particles to settle for approximately 15 minutes. If necessary to clarify, filter or centrifuge at least 0.5 mL of the extract.

ANALYSIS:
Dilute the clarified extract 1:50 with the Sample Diluent using serological pipets (e.g. 0.1 mL extract plus 4.9 mL diluent).
Analyze the diluted extract as the 'sample' according to package insert of the RaPID Assay.

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