title: Titration without Mixing or Dilution:  Sequential Injection of Chemical Sensing Membranes.
abstract: A novel, miniaturized titration was developed using beads 35 μm in diameter as semisolid aqueous titrant retained in a nonaqueous sample stream. Agarose beads with internally bound pH indicator served as a pH sensing membrane material swollen with aqueous NaOH titrant. The indicator monitored the remaining titrant within the agarose beads during perfusion with H(2)SO(4) in 1-butanol samples. Irreversible reaction of 2 mg bead layers was made possible by automated packing and disposal in a flow cell. This strategy substituted membrane advantages for the burdens of mixing and unnecessary dilution under laminar flow conditions. The agarose environment was conditioned with NaCl to tolerate dissolved salt in the sample. Transmittance measurements were made via fiber optics through FEP PTFE optical windows. A simple inverse relationship held between endpoint volume and acid concentration so that calibration curves were linear, R(2) = 0.9980.
authors.affiliation: Center for Process Analytical Chemistry, Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700.
authors.forename: D A
authors.initials: DA
authors.lastname: Holman
authors.forename: G D
authors.initials: GD
authors.lastname: Christian
authors.forename: J
authors.initials: J
authors.lastname: Ruzicka