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 from aqueous samples by thermospray liquid-liquid extraction (TSLLE) was essentially a one-step extraction involving large sample volumes. In this report, recirculative extraction, analysis of small sample volumes, the halide ion effect, and the effect of solvency or solvent modification on the extraction 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 65% after five extraction cycles. When applied to sample volumes of 5-10 mL, TSLLE extracted BAwith a precision of 2.8-6.1%. NaF, NaCl, and NaBr were also used to enhance analyte recovery. NaF gave the best recovery, 104%, for BA relative to the 88% obtained by batch processing. Some improvements in the extraction efficiency was observed when solvent modifiers such as methanol, ethanol, and 2-propanol were used.
Farrell
ES
Miami University, Oxford, Ohio 45056, USA.
Pacey
GE