A spectrophotometric method for the micro-determination of piperonyl butoxide in the presence of pyrethrins.

A rapid spectrophotometric method has been developed for the miclOdetermination
of piperonyl butoxide in the presence of a wide range of
pyrethrins, A solution of the mixture of piperonyJ butoxide and pyrethrins
in a low-boiling fraction of light petroleum is evaporated on a water-bath
until only a small portion of the solvent remains. The final traces of solvent
are removed at 50°C and, to the residue containing piperonyl butoxide and
pyrethrins, 18 per cent. mjV nitric acid is added in order to convert the
piperonyl butoxide content into a soluble yellow-coloured compound. The
quantitative colour reaction has a maximum absorption at 370 nm, and
the method is applicable to the residues in the range 4 to 40 J'g ml-1 of
piperonyl butoxide. The method is also applicable to the residues of formulated
products extracted from grains and paper coatings.