Colorimetric determination of piperazine with p-benzoquinone.

Piperazine (I) and its salts were treated with 1% of p-benzoquinone in 95% ethanol (buffered at pH 5.4) to give a red soln. (max. intensity after 30 min) with an absorption max. at 516 nm. Beer's law was obeyed over the range 2 to 10 µg ml-1 for I and 4 to 20 µg ml-1 for its salts. The ɛ values of I, I dihydrochloride and I phosphate were 9600, and of I citrate 29,700. When applied to three commercial pharmaceutical preparations, mean recoveries were within 1% of those obtained by the official gravimetric method, with coeff. of variation of