Parabene

This publication provides several examples of the use of solid-phase extractions for separating analytes from their matrices. Some of the examples included are caffeine from coffee, polyaromatic hydrocarbons from water, parabens from cosmetics, chlorinated pesticides from water, and steroids from hydrocortisone creams. Extracted analytes maybe determined quantitatively by gas (GC) or liquid chromatography (LG). 

A mixture of methyl paraben, ethyl paraben, propyl paraben, diethyl phthalate, and butyl paraben is separated by HPLC. This experiment emphasizes the development of a mobile-phase composition capable of separating the mixture. A photodiode array detector demonstrates the coelution of the two compounds. 

Preservatives. Most products must contain preservatives to ensure that yeasts, molds, and bacteria do not thrive in them. These preservatives include alcohol, methylparaben, propylparaben, DMDM hydantoin, diazohdinyl urea, and imidazohdinyl urea. The parabens have limited solubiUty in water, eg, 0.25% for methylparaben and 0.05% for propylparaben (22). If these levels are exceeded in the formula, then the addition of solvents is needed to ensure clear, stable products. 

NHydroxyben2oic acid is of significant commercial importance. The most familiar application is the use of several of its esters as preservatives, known as parabens. Also of interest is the use in liquid crystal polymer applications. 

Table 11. Physical Properties of Alkyl />Hydroxybenzoates (Parabens)...

Organic acids may inhibit growth when present in the undissociated form because of their abiHty to change the pH inside the ceU. The most efficient are benzoic acid and sorbic acid, but formic, acetic, and propionic acid also have this effect. The parabens, ie, -hydroxy benzoic acid esters, are also used because of their antimicrobial effect over a broad pH range. 

Perfumes, Flavors, Cosmetics, and Soap. Many naturally occurring esters in essential oils and some synthetic esters are important fragrance and flavor compounds (61,62). They are used in perfumes, flavors, cosmetics, soaps, detergents, and air fresheners. Benzyl, butyl, ethyl, methyl, and phenyl esters of benzoic acid are used as flavors, perfumes, and food preservatives. Glyceryl 4-aminobenzoate [136-44-7] and 2-ethyUiexyl 4-dimethylaminobenzoate [21245-02-3] are used in cosmetic sunscreen preparations. Alkyl esters of 4-hydroxybenzoic acid, called parabens, have been used under various names for fungus infections of the skin, and as preservatives in lotions and creams (101). Soap and cosmetic fragrances use large amounts of amyl and benzyl saHcylate. Benzyl saHcylate [118-58-1] is also used in deodorant sprays. 2-Ethylhexyl saHcylate [118-60-5] and 2-ethylhexyl 4-methoxycinnamate [5466-77-3] are used in sunscreen formulations (102). 

HPLC INVESTIGATION OF pH DEPENDENCY OF THE LIPOPHILICITY PARAMETER OF PARABENS... 

Eigure 13.57 discusses in some detail the use of mobile-phase modifiers to prevent adsorption on PDVB resins. These concepts are very valuable in developing methods. Eor example, note how the observed column efficiencies improve for paraben analysis in the order of methanol < acetonitrile < 50/50 methanol/acetonitrile < THE. Eurthermore, when THE is used the chromato-... 

Citrocarbonate Effervescent Granules—sodium bicarbonate, sodium citrate anhydrous Di-Gel Liquid—aluminum hydroxide, simethicone, saccharin, sorbitol, parabens... 

Extra Strength Maalox Suspension—aluminum hydroxide, magnesium hydroxide, simethicone, parabens, sorbitol, saccharin... 

Gaviscon Extra Strength Reliever Formula Liquid—aluminum hydroxide, magnesium carbonate, parabens, EDTA, saccharin, sorbitol, simethicone, sodium alginate... 

Mylanta Gelcaps—calcium carbonate, magnesium carbonate, parabens... 

Rulox Plus—aluminum hydroxide, magnesium hydroxide, simethicone, sugar, saccharin, dextrose Rulox Suspension—aluminum hydroxide, magnesium hydroxide, parabens, sorbitol, saccharin Simaal Gel 2 Liquid—aluminum hydroxide, magnesium hydroxide, simethicone... 

DDS 100 Plus Capsules—docusate, casanthranol Doxidan Capsules—docusate, casanthranol, sorbitol Nature s Remedy—cascara sagrada, aloe, lactose Peri-Colace—docusate, casanthranol, sorbitol, parabens Senokot-S tablets—docusate, senna concentrate, lactose... 

Some simple foods can be preservatives in their own right. Honey, salt, sugar, lactic acid, and vinegar are all examples of foods that inhibit microbial action. Some health professionals recommend consuming phytoestrogens from foods such as soybeans to achieve various health benefits. The phytoestrogens in the paraben family, found in blueberries, kill molds and fungi and are often added to food as preservatives. 

Imidazolidinyl urea kills gram-negative bacteria. It acts synergistically with parabens to provide a broad-spectrum antibiotic that is effective against mold, yeast, and bacteria. The combination of the two chemicals constitutes the most widely used preservative in cosmetics. 

Parabens are phytoestrogens found in plants such as blueberries they are used as preservatives in food, cosmetics, sunscreens, shampoos, and many other products. 

Parabens kill molds and fungi. They are used synergistically with bactericides to make broad-spectrum antimicrobials. 

These parabens, the methyl, ethyl, propyl and butyl esters, are less readily ionized having pK values in the range 8-8.5 and exhibit good preservative activity even at pH... 

The use of preservative eombinations may be used to extend the range and speetrum of preservation. Thus, in the series of alkyl esters of 4-hydroxybenzoic (/ -hydroxybenzoic) acid (parabens), water solubility deereases in the order methyl, ethyl, propyl and butyl ester. By eombining these produets it is possible to aehieve a situation where both the aqueous and oil phase of an emulsion are proteeted. 

Combinations may also be used to extend the speetrum of a preservative system. Thus, the preservative Germall 115 has an essentially antibacterial activity and very low, if not zero, antifungal aetivity. By combining Germall 115 with parabens, whieh possess antifungal activity, a broader spectrum (antibacterial/antifungal) preservative system is obtained. 

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