Parachlorobenzoic acid

Assessment of indomethacin powder had been specified in the U.J5. XIX and the British Pharmacopeia, 1980 as a back titration with hydrochloric acid after alkaline hydrolysis(13,14). This method can attain a precision of + 0.8%(62). A direct titration for tablets and capsules is described using sodium hydroxide. If performed rapidly with phenolphthalein indicator, a precision of +0.3% is attainable. 8 The latter procedure serves to differentiate ester formation as well as hydrolysis products from intact material. The presence of parachlorobenzoic acid and 5-methoxy-2-methylindole-3-acetic acid are cause for positive error. 

The eight groups of nonsteroidal anti-inflammatory drugs are salicylates, parachlorobenzoic acid derivatives, pyrazolone derivatives, propionic acid derivatives, fenamates, oxicams, phenylacetic acid, and selective COX-2 inhibitors. 

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