Piperazine-1,4-bis 2-ethanesulfonic

A multiple nonreactive tracer technique was utilized to identify physical nonequilibrium processes, e.g., coupled preferential flow and matrix dif ion (21, 24, 25). Three nonreactive tracers, Br, pentafluorobenzoic acid (PFBA), and piperazine-1,4-bis(2-ethanesulfonic acid) (PIPES), were used, which differ only in their flee water molecular difiiision coefficient, thus physical nonequilibrium may be inferred by observed sqiaration of the tracers. Influent concentrations of the nonreactive tracers were O.S mM (Br, PFBA) and 1-0 mM (PIPES). Only Bf was utilized in the repacked column eiqieriments, because physical nonequilibrium as a result of sedimentary stracture is eiqiected to be minimal in repacked media. Analyses were acconqilished using UV detection (190 nm) and low pressure liquid chromatography (Model DX-600, Dionex Corp, Sunnyvale, CA). 

Piperazine-l,4-bis(2-ethanesulfonic acid) (PIPES) buffer Dissolve 1.385 g PIPES (Sigma) and 0.235 g sodium acetate (Merck) in 20 ml demineralized water. 

The poly(l-methylpyrrole) and PEDOT films doped with Piperazine-l-4-bis(2-ethanesulfonic acid (PMPy-PlPES as well as PEDOT-PIPES films) were deposited potentiostatically from saturated PIPES solution (about 0.005 M) and 0.1 M MPy or 0.01 M EDOT. The applied potential was equal to 900 mV for PMPy film deposition and 1050 mV for PEDOT film deposition, and the deposition time was (usually) equal to 600 s. 

Py pyrrole, MPy 1-methylpyrrole, PPy polypyrrole, PMPy poly(l-methylpyrrole), EDOT 3,4-ethylenedioxytiophene, PEDOT poly(3,4-ethylenedioxytiophene), MT 3-methylthiophene, PMT poly(3-methylthiopliene), NaPSS sodium polystyrene sulfonate, NaDBS sodium dodecylbenzenesulfonate, NaPTS sodium para-toluene sulfonate, BSA benzenesulfonic acid, SSA 2-hydroxy-5-sulfobenzoic acid, MES 2-(Af-morpholino) ethanesulfonic acid, MOPS 3-(Al-morpholino) propanesulfonic acid, PIPES piperazine-l,4-bis(2-ethanesulfonic) acid, MeCN acetonitrile, DCE 1,2-dichloroetane, BU4NPF6 tetrabutylammonium hexafluor-ophosphate, BTPPA-CIO4 bis(triphenylphosphoranylidene)ammonium perchlorate, BTPPA-TFPB bis(triphenylphosphoranylidene)ammonium tetrakis[3,5-bis (trifluoromethyl)phenyl]borate, TPenA tetraphenylammonium... 

PIPES solution 120 roM NaCl, 5 mM KCl, 1 mM MgClj, I mM CaClj, 25 mM D-glucose, 20 m PIPES (piperazine-A A -bis-[2-ethanesulfonic acid]), pH 7.0, adjusted with NaOH. Osmolarity adjusted to 320 mosM with sucrose (see Notes 3 and 4). 

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