Identification and determination of p-hydroxybenzoic acid, its esters and 4-methoxicynnamic acid derivatives

p-Hydroxybezoic esters (parabens, PHB) are used as stabilizers in cosmetic preparations. Typical concentrations are 0.1 – 0.3% methylparaben and 0.05 – 0.15% propyparaben respectively. 4-Methoxycinnamic esters in a concentration of about 2% serve as light absorbing agents in sun screen and tanning lotions. Substrates of such cosmetics are usually emulsions or mixtures of waxes and oils.
Also parabens are added in concentrations of up to 0.3% to stabilize many kinds of food.
Described here is the analysis procedure for cosmetic preparations, including sample preparation.