(pye ree' thrum).
» Pyrethrum Extract is a mixture of three naturally occurring, closely related insecticidal esters of chrysanthemic acid (Pyrethrins I: jasmolin I, cinerin I, and pyrethrin I) and three closely related esters of pyrethric acid (Pyrethrins II: jasmolin II, cinerin II, and pyrethrin II). It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of pyrethrins (sum of Pyrethrins I and Pyrethrins II). The ratio of Pyrethrins I to Pyrethrins II in the Extract is not less than 0.8 and not more than 2.8. It may contain pigments characteristic of chrysanthemum species, triglyceride oils, terpenoids, and carotenoid. It may also contain suitable solvents and antioxidants. It contains no other added substances.
Packaging and storage Preserve in tight, light-resistant containers.
USP Reference standards 11
Identification The retention times of the major peaks in the chromatogram of the Assay preparation correspond to those in the chromatogram of the Standard preparation, as obtained in the Assay.
Mobile phase Prepare a filtered and degassed mixture of hexanes and tetrahydrofuran (97.75:2.25). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Dissolve an accurately weighed quantity of USP Pyrethrum Extract RS in hexanes, and dilute stepwise with hexanes to obtain a solution having a known concentration of about 0.5 mg of pyrethrins per mL.
Assay preparation Transfer an accurately weighed quantity of Extract, equivalent to about 50 mg of pyrethrins, to a 100-mL volumetric flask, dilute with hexanes to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L10. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the individual pyrethrin peaks is not less than 2.0; and the relative standard deviation for replicate injections is not more than 1.0%.
Procedure Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the six major peaks. The relative retention times are about 0.78 to 0.80 for jasmolin I; 0.86 to 0.87 for cinerin I; 1.0 for pyrethrin I; 1.95 to 2.15 for jasmolin II; 2.15 to 2.4 for cinerin II; and 2.55 to 2.88 for pyrethrin II. Calculate the quantity, in mg, of pyrethrins in the portion of Extract taken by the formula:
100S[CSi(rUi / rSi)]in which CSi is the concentration, in mg per mL, of the individual pyrethrin of interest in the Standard preparation; and rUi and rSi are the peak responses obtained from the Assay preparation and the Standard preparation, respectively. Calculate the ratio of Pyrethrins I to Pyrethrins II in the portion of the Extract taken by the formula:
A/Bin which A and B are the sums of the quantities of Pyrethrins I and Pyrethrins II, respectively.
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USP35NF30 Page 4489