Hydrophobic-hydrophilic ionic liquids for the extraction and determination of metal ions with water-soluble reagentsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ay01914a

Tetraoctylammonium N -lauroyl sarcosinate and trioctylmethylammonium salicylate are water-immiscible solvents which contain a large amount of dissolved water and may be called "hydrophobic-hydrophilic" ionic liquids (HHILs). We found that several representative water-soluble reagents - Arsenazo I, Arsenazo III, Alizarin Red S, Nitroso-R salt, and Xylenol Orange - are strongly partitioned into the HHIL phase from aqueous solutions over a wide pH range. Metal ions that form complexes with these reagents are extracted efficiently from aqueous solutions. We studied the details of extraction in two representative systems, Sc( iii ) with Arsenazo III and Co( ii ) with Nitroso-R salt. A sensitive, selective, and rapid procedure for the extraction-photometric determination of cobalt with HHILs and Nitroso-R salt has been developed. Water-immiscible water-rich ionic liquids + water-soluble analytical reagents = a novel extraction-based platform for the determination of metal ions.