Metrifonate
;)
Phosphonic acid,(2,2,2-trichloro-1-hydroxyethyl)-,dimethyl ester.
Dimethyl (2,2,2-trichloro-1-hydroxyethyl)phosphonate [52-68-6].
»Metrifonate contains not less than 98.0percent and not more than 100.5percent of C4H8Cl3O4P,calculated on the anhydrous basis.
Packaging and storage—
Preserve in well-closed containers at a temperature not exceeding 25
.
.
Labeling—
Label it to indicate that it is for veterinary use only.
USP Reference standards á11ñ—
USP Metrifonate RS.
Completeness of solution á641ñ:
meets the requirements,0.5g of it being dissolved in methanol.
Color of solution á631ñ—
The solution obtained in the test for Completeness of solutionhas no more color than Matching Fluid F.
Identification—
A:
Infrared Absorption á197Kñ.
B:
Thin-Layer Chromatographic Identification Test á201ñ—
Test solution:
Dissolve 10mg of Metrifonate in methanol,and dilute with methanol to 10.0mL.
Developing solvent sytstem:
a mixture of toluene,dioxane,and glacial acetic acid (70:25:5)
Procedure—
Proceed as directed in the chapter.After allowing the plate to air-dry,spray the plate with a 5%solution of 4-(p-nitrobenzyl)pyridine in acetone,and heat at 120for 15minutes.Before the plate cools,spray it with a 10%solution of tetraethylenepentamine in acetone,and immediately examine the plate:the principal spot in the chromatogram obtained from the Test solutioncorresponds in RFvalue,size,and blue color to that in the chromatogram obtained from the Standard solution.
for 15minutes.Before the plate cools,spray it with a 10%solution of tetraethylenepentamine in acetone,and immediately examine the plate:the principal spot in the chromatogram obtained from the Test solutioncorresponds in RFvalue,size,and blue color to that in the chromatogram obtained from the Standard solution.
C:
Dissolve 20mg of Metrifonate in 1mLof 2Nsodium hydroxide,add 1mLof pyridine,shake,and heat on a water bath for 2minutes:a red color develops in the pyridine layer.
D:
To 100mg of Metrifonate add 0.5mLof nitric acid,0.5mLof a 50%solution of ammonium nitrate,and 0.1mLof 30percent hydrogen peroxide,and heat on a water bath for 10minutes.Heat to boiling,and add 1mLof ammonium molybdate TS:a yellow color precipitate is formed.
Acidity—
Dissolve 2.5g of it in carbon dioxide-free water,dilute with carbon dioxide-free water to 50mL,and add 0.1mLof methyl red TS.Not more than 1.0mLof 0.1Nsodium hydroxide is required to change the color of the indicator.
Water,Method Iá921ñ:
not more than 0.3%.
Heavy metals á231ñ:
0.001%.
Limit of free chloride—
Dissolve 5.0g of Metrifonate in 30mLof alcohol,and add a mixture of 100mLof water and 15mLof nitric acid.Titrate with 0.1Nsilver nitrate VS,determining the endpoint potentiometrically using a silver electrode.Not more than 0.7mLof 0.1Nsilver nitrate is consumed (0.05%).
Chromatographic purity—
Solution A—
Dissolve 1.36g of monobasic potassium phosphate in water,and dilute with water to 1000mL.Adjust with phosphoric acid to a pHof 3.0.
Solution B—
Use acetonitrile.
Mobile phase—
Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Diluent—
Prepare a mixture of acetonitrile and water (1:1).
Standard preparation—
Prepare a solution of USP Metrifonate RSin Diluentcontaining 20mg per mL.
Test solution—
Transfer 500mg of Metrifonate,accurately weighed,to a 25-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.
Chromatographic system (see Chromatography á621ñ)—
The liquid chromatograph is equipped with a 210-nm detector and a 4-mm ×25-cm column that contains 5-µm packing L7.The column is maintained at a constant temperature of about 40.The flow rate is about 1.5mLper minute.The chromatograph is programmed as follows.
.The flow rate is about 1.5mLper minute.The chromatograph is programmed as follows.
| Time (minutes) |
Solution A
(%) |
Solution B
(%) |
Elution |
| 0 | 90 | 10 | equilibration (10minutes) |
| 0–5 | 90 | 10 | isocratic |
| 5 | 90®85 | 10®15 | step gradient |
| 5–25 | 85 | 15 | isocratic |
| 25 | 85®45 | 15®55 | step gradient |
| 25–end* | 45 | 55 | isocratic |
|
*
The elution concludes at 3times the retention time of metrifonate.
|
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Procedure—
Separately inject equal volumes (about 50µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak areas.Calculate the percentage of each impurity taken by the formula:
100F(ri/rS),
in which Fis a response factor,being 0.38for the desmethylmetrifonate peak,if present at a retention time of 0.5relative to that of Metrifonate,0.03for the dichlorvos peak,if present,at a retention time of 1.9relative to that of Metrifonate,and 1.0for any other impurity;riis the peak area for the individual impurity obtained from the Test solution;and rSis the peak area for Metrifonate obtained from the Standard solution:not more than 1.0%of desmethylmetrifonate,0.2%of dichlorvos,and 0.5%of any other impurity are found;and a total of not more than 1.0%of impurities other than desmethylmetrifonate and dichlorvos is found.
Assay—
Dissolve about 300mg of Metrifonate,accurately weighed,in 30mLof alcohol.Add 10mLof monoethanolamine,and allow to stand for 1hour at 21±1.Cool while adding a mixture of 100mLof water and 15mLof nitric acid.While maintaining the temperature at 21±1,titrate with 0.1Nsilver nitrate VS,determining the endpoint potentiometrically using a silver electrode.Each mLof 0.1Nsilver nitrate is equivalent to 25.74mg of C4H8Cl3O4P.
.Cool while adding a mixture of 100mLof water and 15mLof nitric acid.While maintaining the temperature at 21±1,titrate with 0.1Nsilver nitrate VS,determining the endpoint potentiometrically using a silver electrode.Each mLof 0.1Nsilver nitrate is equivalent to 25.74mg of C4H8Cl3O4P.
Auxiliary Information—
Staff Liaison:Ian DeVeau,Ph.D.,Senior Scientist
Expert Committee:(VET)Veterinary Drugs
USP28–NF23Page 1284
Pharmacopeial Forum:Volume No.26(6)Page 1576
Phone Number:1-301-816-8178