Trl-n-octyltln chlorlde acts as a neutral carrler for anlons. Llquld membranes contalnlng thls carrler, ( R ,R )-2,3dlmeth-oxysuccinic acld bls( 1-butylpentyl) ester as plastlclzer, and poly(vlny1 chlorlde) as membrane malrlx show selectlvlly patterns whlch are not In accordance with the sequence obtained for classlcal anlon exchangers. These neutral carrler membranes dlsplay Nernstian electrode functlons for dlfferenl anlons In the I O 9 M to IO-' M concentratlon range. NMR and vapor pressure osmometry studles lndlcate an lnteractlon of the tln organlc compound wlth the chlorlde anlon. The expected mlgrallon of the tin organic compound In the dlrectlon of the anode is demonstrated with an electrodlalytlc transport experlment.A large number of anion-selective liquid membrane electrodes based on classical ion exchangers such as quaternary ammonium salts, phosphonium salts, complexes of 0-phenanthroline, and of other complexing agents have been described (1-4). Electrodes have been proposed for the analysis of Cl-(5-9), NO, (3,9, IO), SCN-(11-13) and other inorganic as well as organic anions. For electrodes based on tetraalkylammonium salts, 35 different detectable anions have been mentioned in ref 1. Usually all these electrodes exhibit roughly the same selectivity sequence with a preference of lipophilic and a rejection of hydrophilic anions (14, 15). In these cases, the free energy of transfer of the anions from the aqueous sample phase to the membrane phase-and therefore the membrane selectivity-is controlled by the free energy of hydration of these ions (4,16-20). This is in contrast to neutral carrier based systems for cations, where the ion selectivity highly depends on the free energy of the interaction of the ions with the ligand (14,21). In the latter case, a wide variety of ion selectivities is made accessible (22).Tin organic compounds have been used as components in anion selective electrodes with response t o C1-(23), HAs0,2-IH2As04-(N), NO, (W), and other species. Although tripropyl tin chloride (26) and other triorgano tin compounds (27) have been found to influence anion transport, it has not yet been properly proved that such tin organic compounds may act as neutral carriers for anions. In this paper, we show that trioctyltin chloride displays anion carrier properties if incorporated in solvent polymeric membranes.
EXPERIMENTAL SECTIONCell Assemblies for EMF Studies. For all EMF measurements, cells of the following type were used: Hg, Hg2C12; KC1 (satd)llM LiOAclsample solution llmembrane 110.01 M NaC1; AgC1, Ag The external reference electrode was a double junction saturated calomel electrode with a ceramic diaphragm (for details see ref 28). Measurements were performed with four different membranes of the following compositions: (a) 6 wt % methyltri-ndodecylammonium chloride (MTDDACl), 65 wt % di-n-butyl phthalate (DBP), 29 wt % poly(viny1 chloride) (PVC); (b) 3 wt % MTDDACI, 49 wt % (R,R)-2,3-dimethoxysuccinic acid bis(1-butylpentyl) ester (DMSNE), 48 wt % PVC; (c) 3 wt % tri-noctyltin chloride...