(gwye fen' e sin).
» Guaifenesin contains not less than 98.0 percent and not more than 102.0 percent of C10H14O4, calculated on the dried basis.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 40 µg per mL.
C: Mix about 5 mg with 1 drop of formaldehyde and a few drops of sulfuric acid: a deep cherry red to purple color is produced.
Melting range 741: between 78 and 82, but the range between beginning and end of melting does not exceed 3.
Loss on drying 731 Dry it in vacuum, but at a pressure not below 10 mm of mercury, at 60 to constant weight: it loses not more than 0.5% of its weight.
Heavy metals, Method I 231 The limit is 0.0025%.
Solution A, Solution B, and Mobile phase Proceed as directed in the Assay.
Chromatographic system Proceed as directed in the Assay. To evaluate the system suitability requirements, use the Resolution solution and the Standard preparation prepared as directed in the Assay.
Test solution Dissolve about 20 mg of Guaifenesin in 10 mL of Solution B.
Diluted test solution Transfer 1.0 mL of the Test solution to a 100-mL volumetric flask, dilute with Solution B to volume, and mix.
Procedure Separately inject equal volumes (about 10 µL) of the Test solution and the Diluted test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks. All of the peaks are baseline resolved. Calculate the percentage of each impurity in the portion of Guaifenesin taken by the formula:
F(ri / rS)in which F is a response factor equal to 0.63 for the guaiacol peak, having a relative retention time of 1.4, and 1.0 for all other impurities; ri is the area of each peak, other than that of the main guaifenesin peak, obtained from the Test solution; and rS is the area of the main peak obtained from the Diluted test solution: not more than 1.5% of 2-(2-methoxyphenoxy)-1,3-propanediol (guaifenesin -isomer), the peak for which occurs at a relative retention time of about 0.9, is found; not more than 0.03% of guaiacol is found; not more than 0.5% of any other individual impurity is found; and not more than 1.0% of total impurities, excluding guaifenesin -isomer and guaiacol, is found.
Solution A Prepare a mixture of water and glacial acetic acid (990:10).
Solution B Use acetonitrile.
Mobile phase Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).
Resolution solution Prepare a solution in Solution B containing about 0.5 mg of USP Guaifenesin RS and 0.02 mg of USP Guaiacol RS in each mL.
Standard preparation Prepare a solution of USP Guaifenesin RS in Solution B having a known concentration of about 0.5 mg per mL.
Assay preparation Transfer about 25 mg of Guaifenesin, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Solution B to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 276-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. The chromatograph is programmed as follows.
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 peak responses. Calculate the quantity of C10H14O4 in the portion of Guaifenesin taken by the formula:
50C(rU / rS)in which C is the concentration, in mg per mL, of USP Guaifenesin RS in the Standard preparation; and rU and rS are the peak areas obtained from the Assay preparation and the Standard preparation, respectively. Calculate the percentage of C10H14O4 in the portion of Guaifenesin taken. To this value, add the percentage of guaifenesin -isomer found in the test for Chromatographic purity.
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USP35NF30 Page 3380Pharmacopeial Forum: Volume No. 27(4) Page 2735