A supported liquid membrane (SLM) with resorcinarene for facilitated transport of methyl glycopyranosides: Parameters and mechanism relating to the transport

A supported liquid membrane (SLM) containing a resorcinarene carrier, previously used for the transport of aldoses and alditols, has been used for the selective transport of methyl-α-d-glucopyranoside, methyl-β-d-glucopyranoside, methyl-β-d-galactopyranoside, methyl-α-d-mannopyranoside, and methyl-β-d-xylopyranoside from concentrated (0.20–0.025 M) aqueous solutions. The membrane is made of a microporous polytetrafluoroethylene film (PTFE), impregnated with a 0.01 M solution of the carrier in CCl4. The permeabilities of the SLM for all studied methyl aldopyranosides were calculated. On the basis of the flux dependence on the initial concentrations of carrier and methyl aldopyranoside, the rate-determining step in the transport mechanism is shown to be the migration of the (1/1) carrier–carbohydrate complex in the immobilized organic phase. The flux of sugar is related to the initial concentration of methyl aldopyranoside in the feed phase by a saturation law, which allowed the determination of the apparent diffusion coefficients and the stability constants of the resorcinarene complexes of methyl aldopyranosides formed in the liquid membrane. The stability constants of the complexes fall into two classes: aldopyranosides with trans HO groups form complexes of low stabilities (K ≈ 0.36 ± 0.01) whereas aldopyranosides with cis HO groups form complexes of high stabilities (K ≈ 0.84 ± 0.01).