Sample preparation and analysis

Quantitatively transfer the retained one-tenth of the suspension to a 50-ml volumetric flask, rinsing several times with small quantities of acetonitrile. Dilute to about 1cm below the mark and place the flask in an ultrasonic bath for 15 minutes to dissolve the deltamethrin (a volume contraction occurs) and wait for 15 minutes. Make up to volume with acetonitrile and mix thoroughly. Filter rapidly to avoid any solvent loss or centrifuge. The extract, which must be clear, is used for the analysis.

Inject 20(il of the calibration solution until the peak areas (or heights) of two successive injections agree to within 5%. Inject the sample solution. The peak area (or height) for the sample solution must not differ by more than 20% from the peak area (or height) for the deltamethrin calibration solution. If it differs, adjust the volume of the sample to meet this requirement or prepare another calibration solution with an adapted deltamethrin content. If not, inject the calibration solution and the sample solution in duplicate.

2.3.6 Calculation

For each of the two calibration-solution-versus-sample-solution groups, calculate the deltamethrin content (m,mg) in the retained one-tenth of the suspension from the equation:

a0 x 10

where a0 = deltamethrin area (or height) of the calibration solution ai = deltamethrin area (or height) of the sample solution m{) = mass of deltamethrin standard in the calibration solution

The values m, in the duplicate determinations must agree to within 5% of their mean. From the value obtained in section 2.1.7 for deltamethrin content, calculate the mass of deltamethrin in the initial sample taken for the suspensibility test.

where ra, = mass of deltamethrin found in the retained one-tenth of the suspension (mg) m2 = mass of deltamethrin in the initial sample taken to prepare the suspension (mg)

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