Continuous flow liquid membrane extraction: a novel automatic trace-enrichment technique based on continuous flow liquid–liquid extraction combined with supported liquid membrane

Abstract

Combining the continuous flow liquid-liquid extraction (CFLLE) and supported liquid membrane (SLM) extraction, a novel aqueous-aqueous extraction technique that we termed continuous flow liquid membrane extraction (CFLME) is developed for trace-enrichment. The analyte was firstly extracted into the organic phase in the CFLLE step, then transported onto the organic liquid membrane that formed on the surface of the micro porous membrane of the SLM equipment. Finally, it passed through the liquid membrane and was trapped by the acceptor. Aspects related to CFLME were studied by using dichloromethane as liquid membrane, and sulfonylurea herbicides as model compounds. An enrichment factor of over 1000 was obtained when 10 g l −1 of MSM was enriched for 120 min by this technique. The drawbacks of only a few organic solvents can be selected as liquid membrane with a limited lifetime in SLM operation was overcome. In this CFLME method, almost all solvents that used in the conventional liquid-liquid extraction (LLE) can be adopted and the lifetime of liquid membrane is no longer a problem.

Sensitivity enhancement of chlorinated phenols by continuous flow liquid membrane extraction followed by capillary electrophoresis

“…An experiment showed that dichloromethane has a higher enrichment factor for polar sulfonylurea herbicides [12], which was in accordance with the principle of like dissolves like. Dichloromethane was chosen as liquid membrane because chlorinated phenols are polar compounds.…”

“…The whole system setup is similar to those described elsewhere [12,13], but a WZ-50G microinfusion pump (The Medical Instrument Factory of Zhejiang University, China) and a MiniPump (Laboratory Date Control, Division of Milton Roy Company) were employed to deliver dichloromethane and sample solution, respectively. The SLM extraction disk is the same as described elsewhere [17].…”

“…Our research group has developed a new liquid membrane extraction technique named continuous flow liquid membrane extraction (CFLME) for trace enrichment [12,13]. CFLME has intrinsic merits of high enrichment rate, long-term stability, and easy to select liquid membrane -in fact almost all polar organic solvents can be used as organic liquid membrane.…”

“…CFLME has intrinsic merits of high enrichment rate, long-term stability, and easy to select liquid membrane -in fact almost all polar organic solvents can be used as organic liquid membrane. CFLME has been successfully coupled on-line to HPLC for analysis of sulfonylurea herbicides [12,13], and as it is mentioned above that SLM could be also successfully coupled with CE, it should be feasible to couple CFLME online with CE because CFLME and SLM are similar procedures. However, the study of CFLME coupled to CE is still terra incognita.…”

Continuous-flow microextraction and gas chromatographic–mass spectrometric determination of polycyclic aromatic hydrocarbon compounds in water

“…Supported LME [17] is based on a three-phase system with an organic phase sandwiched between two aqueous phases and the organic phase is immobilized in a porous hydrophobic membrane. Continuous-flow LME [18] was developed in order to extract polar substances and prolong the life span of the liquid membrane, which was very easy to realize the automation with HPLC. LPME [19], using a microliter drop of organic solvent on the end of a Teflon rod or the needle tip of a microsyringe, was developed as a cheap pretreatment method.…”