someone worked out a solvent extraction method for _lithium_?! of course it uses some strange bespoke ligand, a substituted pyrazolone (so think, like, antipyrine only fancier) *and* a phosphate ester (which tend to be useful in metal ion extractions, cf. how actinides can be fractionated with tributyl phosphate extraction)
fwiw I was thinking of how solvent-extraction methods could be good for analytical techniques using my shiny new spectrophotometer
https://www.sciencedirect.com/science/article/pii/0039914087800954