Very slightly soluble in water, freely soluble in alcohol and in Methanol.
First identification: A, B.
Second identification: A, C, D.
A. Melts between 125°C and 128°C.
B. The infrared absorption spectrum is concordant with the reference spectrum of methyl paraben or with the spectrum obtained from methyl paraben CRS.
C. Examine the chromatograms obtained in the test for related substances. The principle spot in the chromatogram obtained with test solution (b) is similar in position and size to the principle spot in the chromatogram obtained with reference solution (b).
D. To about 10 mg in a test tube add 1 ml of sodium carbonate solution R, boil for 30 seconds and cool (solution A). To a further 10 mg in a test tube add 1 ml of sodium carbonate solution R, the substance partly dissolves (solution B). Add at the same time to each of solutions A and B 5 ml of aminopyrazolone solution and 1 ml of potassium ferricyanide solution R and mix. Solution B is yellow to orange brown. Solution A is orange to Red, the colour is clearly more intense than any similar colour that may be obtained with solution B
Appearance of solution
Dissolve 1.0 gm in alcohol R and dilute to 10 ml with the same solvent is clear and not more intensely coloured than reference solution prepared by mixing 1.5 ml ferric chloride colorimetric solution, 0.8 ml cobaltous chloride colorimetric solution, 0.2 ml cupric sulphate colorimetric solution and 97.5 ml of 1% w/v HCl solution.
To 2 ml of the Solution S and 3 ml of Alcohol R, 5 ml of carbon dioxide-free water R and 0.1 ml of bromocresol green solution R. Not more than 0.1 ml of 0.1M sodium hydroxide is required to change the colour of the indicator to blue.
Any impurity: Any spot in the chromatogram obtained with Test Solution (a) apart from the principal spot is not more intense than the spot in the chromatogram obtained with reference solution (a) (0.5 %).
System suitability: The test is not valid unless the chromatogram obtained with reference solution (c) shows two clearly separated principal spots.