Methylparaben

         [99-76-3] This product is methyl 4-hydroxybenzoate, esterified from methanol and p-hydroxybenzoic acid. Calculated on the dried basis, it contains C8H8O3 not less than 98.0% and not more than 102.0%.;

        【Description】 This product is white or almost white crystals or crystalline powder. It is freely soluble in methanol and ethanol, soluble in hot water, and slightly soluble in water. Melting point The melting point (General Rule 0612) of this product is 125–128°C.

       【Identification】 (1) In the chromatogram obtained under the Assay, the retention time of the principal peak in the test solution corresponds to that in the reference solution. (2) Dissolve a quantity of the substance in ethanol and dilute to produce a solution containing about 5μg per ml. Measure the absorbance by ultraviolet-visible spectrophotometry (General Rule 0401); a maximum absorption occurs at 258nm. (3) The infrared absorption spectrum is concordant with the reference spectrum (Spectrum 853).

         【Assay】 Determine by high-performance liquid chromatography (General Rule 0512). Chromatographic system Use a column packed with octadecylsilane bonded silica gel; use a mixture of methanol and 1% glacial acetic acid (60:40) as the mobile phase; detection wavelength is 254nm. Separately weigh suitable quantities of methylparaben and ethylparaben CRS, dissolve in the mobile phase and dilute to produce a solution containing 10μg of each per ml. Inject 20μl into the liquid chromatograph and record the chromatogram. The resolution between methylparaben and ethylparaben peaks should meet the requirement. Procedure Weigh accurately a quantity of the substance, dissolve in the mobile phase and dilute quantitatively to produce a solution containing 0.1mg of methylparaben per ml. Inject accurately 20μl into the liquid chromatograph and record the chromatogram. Separately, weigh accurately a quantity of methylparaben CRS, and proceed in the same manner. Calculate the content by the external standard method using the peak areas.

       【Category】 Pharmaceutical excipient, antimicrobial preservative.

        【Storage】 Keep tightly closed.