Liquid-liquid extraction of lead(II) with tributyl phosphate

Tributyl phosphate [30% solution in isobutyl methyl ketone (IBMK)] is used for the quantitative extraction of microgram amounts of lead from 3M hydrochloric acid containing lithium chloride (2M) as salting-out agent. It is then stripped from the organic phase with water and determined colorimetrically as its orange-red complex with 4-(2-pyridylazo)resorcinol at 520 nm. TBP alone cannot quantitatively extract lead in the absence of salting-out agents. The IBMK used as diluent does not extract lead under the conditions used. The period of equilibration needed is 5 min. Lead can be extracted in the presence of up to 100 times as much of certain other ions. The method is found to be applicable to analysis of gun-metal.