title: Isoelectric buffers, part 3: determination of pKa and pI values of diamino sulfate carrier ampholytes by indirect UV-detection capillary electrophoresis.
abstract: Ampholytes with close pK(a) values (i.e., good carrier ampholytes (CAs)) are needed as buffers in pH-biased isoelectric trapping (IET) separations. The syntheses of two families of such good CAs were reported recently. Members of the family of diamino sulfate ampholytes (first series) had pI values in the 5.7 < pI < 9.0 range. Members of the family of quaternary ammonium dicarboxylic acid ampholytes (second series) had pI values in the pI < 4.3 range. To further characterize the diamino sulfate ampholytes, their effective mobilities were measured by indirect UV-absorbance detection capillary electrophoresis in a series of background electrolytes (BGEs) with different pH values. The pK(a) and limiting ionic mobility values of the CAs were obtained by fitting these mobility values, as a function of the pH and the ionic strength of the BGEs, to the theoretical mobility expression. These diamino sulfates complete the list of CAs suitable for IET separations.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA.
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Lalwani
authors.forename: Edward
authors.initials: E
authors.lastname: Tutu
authors.forename: Gyula
authors.initials: G
authors.lastname: Vigh
mesh_terms: D000665:Ampholyte Mixtures / Q000737:chemistry*; D002021:Buffers; D003959:Diamines / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing / Q000379:methods; D007526:Isoelectric Point; D009025:Morpholines / Q000737:chemistry* / Q000302:isolation & purification; D015203:Reproducibility of Results; D013463:Sulfuric Acid Esters / Q000737:chemistry* / Q000302:isolation & purification; D014439:Tyramine / Q000302:isolation & purification
chemical_list: C503727:1,3-bis(4-morpholino)-2-O-sulfopropane; C503728:1,3-bis(N,N-dimethylamino)-2-O-sulfopropane; C503729:1,3-bis(N,N-dipropylamino)-2-O-sulfopropane; D000665:Ampholyte Mixtures; D002021:Buffers; D003959:Diamines; D009025:Morpholines; D013463:Sulfuric Acid Esters; D014439:Tyramine