Amitraz
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C19H23N3 293.41

Methanimidamide,N¢-(2,4-dimethylphenyl)-[[N(2,4-dimethylphenyl)imino]methyl-N]-methyl-.
N-Methyl-N¢-2,4-xylyl-N-(N-2,4-xylylformimidoyl)formamidine.
N-Methylbis(2,4-xylyliminomethyl)amine [33089-61-1].
»Amitraz contains not less than 95.0percent and not more than 101.5percent of C19H23N,calculated on the anhydrous basis.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label it to indicate that it is for veterinary use only.
Identification—
A: Infrared Absorption á197Mñ.
B: Proceed as directed in the test for Related compounds,except to prepare a test solution of Amitraz in toluene containing 2mg per mLand a Standard solutionof USP Amitraz RSin toluene containing 2mg per mL:the RFvalue of the principal spot in the chromatogram obtained from the test solution corresponds to that in the chromatogram obtained from the Standard solution.
C: The retention time of the major peak in the chromatogram of the Reference solutioncorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.
Water,Method Iá921ñ: not more than 0.1%,anhydrous pyridine being used in place of methanol in the titration vessel.
Residue on ignition á281ñ: not more than 0.2%.
Related compounds— Prepare a test solution of Amitraz in toluene containing 100mg per mL.Prepare a solution of USP Amitraz RSin toluene having a concentration of 2.0mg per mL(Standard solution 1).Prepare a solution of 2,4-dimethylaniline in toluene having a concentration of 0.30mg per mL(Standard solution 2).Prepare a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture as follows.Stand the plate to a depth of 3.5cm in a solution prepared by dissolving 35g of acetamide in 100mLof methanol,adding 100mLof triethylamine,and diluting to 250mLwith methanol.Allow to stand the wet plate in a current of cold air for about 30seconds.Immediately apply separately to the plate,at a level about 1cm below the top of the impregnated zone,2µLeach of the test solution,Standard solution 1,and Standard solution 2.Promptly develop the chromatogram in a solvent system consisting of a mixture of cyclohexane,ethyl acetate,and triethylamine (5:3:2)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,allow it to air-dry,and examine it under short-wavelength UVlight.Any secondary spot in the chromatogram obtained from the test solution is not more intense than the spot in the chromatogram obtained from Standard solution 1(2.0%).Expose the plate to the vapor of hydrochloric acid for about 10minutes,then expose it to the vapor of nitrogen dioxide (prepared by the reaction of nitric acid and zinc)for 10minutes,remove any excess nitric oxide by air exhaust,and spray the plate with a 0.5%solution of N-(1-naphthyl)ethylenediamine dihydrochloride in methanol,and examine the plate.Any secondary spot in the chromatogram obtained from the test solution corresponding to 2,4-dimethylaniline is not more intense than the spot in the chromatogram obtained from Standard solution 2(0.30%).
Assay—
Internal standard solution— Prepare a solution of squalane in methyl acetate containing 10mg per mL.
Standard preparation— Quantitatively dissolve an accurately weighed quantity of USP Amitraz RSin Internal standard solutionto obtain a solution having a known concentration of about 8mg of USP Amitraz RSper mL.
Assay preparation— Transfer about 200mg of Amitraz,accurately weighed,to a 25-mLvolumetric flask,add about 20mLof Internal standard solution,and swirl to dissolve.Dilute with Internal standard solutionto volume,and mix.
Reference solution— Prepare a solution of Amitraz in methyl acetate containing about 8mg per mL.
Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 4-mm ×1.5-m column packed with 3%liquid phase G1on support S1A.The column and detector block temperatures are maintained at about 250.Dry nitrogen is used as the carrier gas at a flow rate of about 60mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between squalane and amitraz is not less than 3.0;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 5µL)of the Standard preparation,the Assay preparation,and the Reference solutioninto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C19H23N3in the portion of Amitraz taken by the formula:
25C(RU/RS),
in which Cis the concentration,in mg per mL,of USP Amitraz RSin the Standard preparation;and RUand RSare the ratios of the response of the amitraz peak to the response of the squalane peak obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Ian DeVeau,Ph.D.,Senior Scientist
Expert Committee:(VET)Veterinary Drugs
USP28–NF23Page 134
Phone Number:1-301-816-8178