Improving the recovery of ionic solutes from aqueous media by modified thermospray liquid-liquid extraction

Our previously reported procedure for the extraction of charged compounds f rom aqueous samples by thermospray liquid-liquid extraction (TSLLE) was ess entially a one-step extraction involving large sample volumes. In this repo rt, recirculative extraction, analysis of small sample volumes, the halide ion effect, and the effect of solvency or solvent modification on the extra ction efficiency of benzoic acid (BA) by TSLLE were investigated. Compared to the one-step procedure that resulted in an extraction efficiency of only 28% for BA in n-hexane, recirculative TSLLE resulted in a BA recovery of 6 5% after five extraction cycles. When applied to sample volumes of 5-10 mL, TSLLE extracted BA with a precision of 2.86-6.1%. NaF, NaCl, and NaBr were also used to enhance analyte recovery. NaF gave the best recovery, 104%, f or BA relative to the 88% obtained by batch processing. Some improvements i n the extraction efficiency was observed when solvent modifiers such as met hanol, ethanol, and 2-propanol were used.