Titrimetric estimation of dibutyl phosphate in highly degraded tributyl phosphate samples. [Monobutyl phosphate (MBP)]

In purex process highly degraded TBP samples are often encountered as heavy organics. The conventional methods for the analysis of DBP in these samples involve the separation and conversion of DBP into inorganic phosphate for estimation by spectrophotometry. This procedure being very time consuming a new method has been developed for the estimation of DBP in such samples, which involves the removal of uranium and other heavy elements from the degraded solvent by scrubbing with sulphuric acid and subsequent determination of DBP in the organic layer by an indirect titration using thorium and EDTA. The DBP is first complexed and precipitated with a known excess of thorium nitrate solution and after separating the precipitate by centrifugation the excess thorium in the supernatant is estimated by EDTA titration with xylenol orange as indicator. The amount of thorium consumed during precipitation corresponds to DBP concentration in the molar ratio of 1:4. This method can also be extended to the analysis of MBP if required where the thorium consumed corresponds to MBP concentration in the molar ratio of 1:2. The method has a precision and accuracy of /sup +/-3% in the range 0.08 - 0.8 millimoles of DBP.