Parabens are a class of widely used preservatives in cosmetic and pharmaceutical products. Chemically, they are a series of parahydroxybenzoates or esters of parahydroxybenzoic acid (also known as 4-hydroxybenzoic acid). Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bactericidal and fungicidal properties. They are found in shampoos, commercial moisturizers, shaving gels, personal lubricants, topical/parenteral pharmaceuticals, suntan products, makeup, and toothpaste. They are also used as food additives. Parabens are active against a broad spectrum of microorganisms.
Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216), butylparaben and heptylparaben (E209). Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. All commercially used parabens are synthetically produced, although some are identical to those found in nature. They are produced by the esterification of para-hydroxybenzoic acid with the appropriate alcohol, such as methanol, ethanol, or n-propanol.
Ethylparaben (ethyl para-hydroxybenzoate) is the ethyl ester of p-hydroxybenzoic acid. Its formula is HO-C6H4-CO-O-CH2CH3. It is used as an antifungal preservative. As a food additive, it has E number E214. Sodium ethyl para-hydroxybenzoate, the sodium salt of ethylparaben, has the same uses and is given the E number E215.
Ethylparaben (ethyl para-hydroxybenzoate) is the ethyl ester of p-hydroxybenzoic acid. Its formula is HO-C6H4-CO-O-CH2CH3. It is used as an antifungal preservative. As a food additive, it has E number E214. Sodium ethyl para-hydroxybenzoate, the sodium salt of ethylparaben, has the same uses and is given the E number E215.
Ethyl Hydroxybenzoate BP Grade
Ethyl paraben
Ethyl Parahydroxybenzoate, Ph Eur
C9H10O3 --- 166.2 --- 120-47-8
DEFINITION
Ethyl 4-hydroxybenzoate.
Content: 98.0 per cent to 102.0 per cent.
CHARACTERS
Appearance: White or almost white, crystalline powder or colourless crystals.
Solubility: Very slightly soluble in water, freely soluble in alcohol and in methanol.
IDENTIFICATION
First identificationıA, B.
Second identificationıA, C, D.
A. Melting point 115C to 118C.
B. Infrared absorption spectrophotometry. Comparison ethyl parahydroxybenzoate CRS.
C. Examine the chromatograms obtained in the test for related substances.
Results: The principal spot in the chromatogram obtained with test solution (b) is similar in
position and size to the principal 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, boil for 30 s and cool
(solution A). To a further 10 mg in a similar test-tube add 1 ml of sodium carbonate solution; the
substance partly dissolves (solution B). Add at the same time to solution A and solution B 5 ml of
aminopyrazolone solution and 1 ml of potassium ferricyanide solution and mix. Solution B is yellow
to orange-brown. Solution A is orange to red, the colour being clearly more intense than any similar
colour which may be obtained with solution B.
TESTS
Solution S: Dissolve 1.0 g in alcohol and dilute to 10 ml with the same solvent.
Appearance of solution: Solution S is clear and not more intensely coloured than reference
solution.
Acidity: To 2 ml of solution S add 3 ml of alcohol, 5 ml of carbon dioxide-free water and 0.1
ml of bromocresol green solution. Not more than 0.1 ml of 0.1 M sodium hydroxide is required to
change the colour of the indicator to blue.
Related substances: To pass the test (0.5 per cent).
Sulphated ash: Maximum 0.1 per cent, determined on 1.0 g.
ASSAY
To 1.000 g add 20.0 ml of 1 M sodium hydroxide. Heat at about 70C for 1 h. Cool rapidly in an ice
bath. Prepare a blank in the same manner. Carry out the titration on the solutions at room
temperature. Titrate the excess sodium hydroxide with 0.5 M sulphuric acid , continuing the
titration until the second point of inflexion and determining the end-point potentiometrically.
1 ml of 1 M sodium hydroxide is equivalent to 166.2 mg of C9H10O3.
IMPURITIES
A. R = H: 4-hydroxybenzoic acid,
B. R = CH3: methyl 4-hydroxybenzoate,
C. R = CH2-CH2-CH3: propyl 4-hydroxybenzoate,
D. R = CH2-CH2-CH2-CH3: butyl 4-hydroxybenzoate.
Ethylparaben USP NF Grade
C9H10O3 --- 166.17
Benzoic acid, 4-hydroxy-, ethyl ester.
Ethyl p-hydroxybenzoate [120-47-8].
Ethylparaben contains not less than 98.0 percent and not more than 102.0 percent of C9H10O3.
Identification:
A: Infrared Absorption 197M .
B: Melting range: between 115Cand 118C.
Color of solution: Dissolve 1 g in alcohol, dilute with alcohol to 10 mL, and mix
(Ethylparaben solution). This solution is clear and not more intensely colored than alcohol or a
solution prepared immediately before use by mixing 2.4 mL of ferric chloride CS, 1.0 mL of cobaltous
chloride, and 0.4 mL of cupric sulfate with 0.3 N hydrochloric acid to make 10 mL, and diluting 5 mL
of this solution with 0.3 N hydrochloric acid to make 100 mL. Make the comparison by viewing the
solutions downward in matched color-comparison tubes against a white surface.
Acidity: To 2 mL of Ethylparaben solution prepared in the Color of solution test add 3 mL of
alcohol, 5 mL of carbon dioxide-free water, and 0.1 mL of bromocresol green, and titrate with 0.10 N
sodium hydroxide: not more than 0.1 mL is required to produce a blue color.
Residue on ignition: not more than 0.1%, determined on 1.0 g.
Related substances: To pass the test.
Assay: Transfer about 1.000 g of Ethylparaben, accurately weighed, to a flask fitted with a
ground-glass stopper. Add 20.0 mL of 1 N sodium hydroxide, and heat at about 70 for 1 hour. Cool
rapidly in an ice bath. Carry out the titration of the solutions at room temperature. Titrate the
excess sodium hydroxide with 1 N sulfuric acid, continuing the titration until the second point of
inflection and determining the endpoint potentiometrically. Perform a blank determination. Each mL
of 1 N sodium hydroxide is equivalent to 166.2 mg of C9H10O3.
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