Carbomer 934P
»Carbomer 934Pis a high molecular weight polymer of acrylic acid cross-linked with allyl ethers of sucrose or pentaerythritol.Carbomer 934P,previously dried in vacuum at 80for 1hour,contains not less than 56.0percent and not more than 68.0percent of carboxylic acid (–COOH)groups.The viscosity of a neutralized 0.5percent aqueous dispersion of Carbomer 934Pis between 29,400and 39,400centipoises.
Packaging and storage— Preserve in tight containers.
Identification—
A: Prepare a 1in 100dispersion of it.To one portion of the dispersion add thymol blue TS:an orange color is produced.To another portion of the dispersion add cresol red TS:a yellow color is produced.
B: Adjust a 1in 100dispersion of it with 1Nsodium hydroxide to about pH7.5:a very viscous gel is produced.
Viscosity á911ñ— Carefully add 2.50g,previously dried in vacuum at 80for 1hour,to 500mLof water in a 1000-mLbeaker,while stirring continuously at 1000±10rpm,with the stirrer shaft set at an angle of 60and to one side of the beaker,with the propeller positioned near the bottom of the beaker.Allow 45to 90seconds for addition of the test preparation at a uniform rate,being sure that loose aggregates of powder are broken up,and continue stirring at 1000±10rpm for 15minutes.Remove the stirrer,and place the beaker containing the dispersion in a 25±0.2water bath for 30minutes.Insert the stirrer to a depth necessary to ensure that air is not drawn into the dispersion,and,while stirring at 300±10rpm,titrate (see Titrimetry á541ñ)with a calomel-glass electrode system to a pHof between 7.3and 7.8by adding sodium hydroxide solution (18in 100)below the surface,determining the endpoint potentiometrically.The total volume of sodium hydroxide solution (18in 100)used is about 6.2mL.Allow 2to 3minutes before final pHdetermination.[NOTE—If the final pHexceeds 7.8,discard the mucilage,and prepare another using a smaller amount of sodium hydroxide for titration.]Return the neutralized mucilage to the 25water bath for 1hour,then perform the viscosity determination without delay to avoid slight viscosity changes that occur 75minutes after neutralization.Equip a suitable rotational viscosimeter with a spindle having a cylinder 1.47cm in diameter and 0.16cm high attached to a shaft 0.32cm in diameter,the distance from the top of the cylinder to the lower tip of the shaft being 3.02cm,and the immersion depth being 4.92cm (No.6spindle).With the spindle rotating at 20rpm,observe and record the scale reading.Calculate the viscosity,in centipoises,by multiplying the scale reading by the constant for the spindle used at 20rpm.
Loss on drying á731ñ— Dry it in vacuum at 80for 1hour:it loses not more than 2.0%of its weight.
Limit of benzene—
Standard solution— Dissolve an accurately weighed quantity of benzene quantitatively in methanol to obtain a solution having a known concentration of about 0.2mg per mL.Dilute this solution quantitatively with organic-free water (see Organic Volatile Impurities á467ñ)to obtain a solution having a known concentration of about 1.0µg per mL.
Test solution— Transfer about 1g of Carbomer 934P,accurately weighed,to a 100-mLvolumetric flask.Add about 75mLof sodium chloride solution (2in 100),and mix by mechanical means until homogenous (usually about 30minutes).Dilute with sodium chloride solution (2in 100)to volume,and mix until homogenous (usually less than 1minute).[NOTE—This preparation must be analyzed within 3hours of preparation.]
Chromatographic system (see Chromatography á621ñ)—The gas chromatograph is equipped with a flame-ionization detector,a 0.53-mm ×30-m fused silica analytical column coated with a 3.0-µm G43stationary phase,a 0.53-mm ×5-m silica guard column deactivated with phenylmethyl siloxane,and a splitless injection system.The carrier gas is helium flowing at a linear velocity of about 35cm per second.The injection port and detector temperatures are maintained at 140and 260,respectively.The column temperature is programmed according to the following steps:it is held at 40for 20minutes,then increased at 50per minute to 260,and held at 260for 20minutes.Chromatograph the Standard solution,and record the responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 15%.
Procedure— Separately inject equal volumes (about 4µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the benzene peaks.Calculate the percentage of benzene in the portion of Carbomer 934Ptaken by the formula:
10(C/W)(rU/rS),
in which Cis the concentration,in µg per mL,of benzene in the Standard solution;Wis the weight,in mg,of Carbomer 934Ptaken to prepare the Test solution;and rUand rSare the benzene peak responses obtained from the Test solutionand the Standard solution,respectively:not more than 0.01%is found.
Organic volatile impurities,Method IVá467ñ: meets the requirements for chloroform,1,4-dioxane,methylene chloride,and trichloroethylene.
Assay for carboxylic acid content— Slowly add about 400mg previously dried and accurately weighed,to 400mLof water in a 1000-mLbeaker,while stirring continuously at about 1000rpm,with the stirrer shaft set at an angle of 60and at the side of the beaker,with the propeller positioned near the bottom of the beaker,and continue stirring for 15minutes.Reduce the stirring speed,and titrate potentiometrically with 0.25Nsodium hydroxide VS,using a calomel-glass electrode system.Allow 1minute for mixing,after each addition of 0.25Nsodium hydroxide VS,before recording the pH.Calculate the carboxylic acid content as a percentage of carboxylic acid groups taken by the formula:
100(45.02VN/W),
in which Vis the volume,in mL,of sodium hydroxide consumed;Nis the normality of the sodium hydroxide solution;Wis the weight,in mg,of specimen taken;and 45.02is the molecular weight of the carboxylic acid (–COOH)group.
Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2973
Phone Number:1-301-816-8262