Electropreconcentration‐induced local pH change

Abstract

Ion-permselective nanochannel-based sample preconcentration or electropreconcentration has been demonstrated as an effective technique for concentrating charged analytes at the interface between a micro- and nanochannel. The anion-selective electropreconcentration involves extraction of hydroxide in the preconcentrated sample plug, resulting in pH decrease. We investigated the pH change in a microchannel using charged pH indicators with different conditions including running buffer pH, sample channel electric field, and salt concentration. The anion-selective preconcentration showed pH decrease from 11 to under 7 in the preconcentrated sample plug. Therefore, careful design and interpretation are required with pH-dependent experiments such as analyzing enzyme or antibody characteristics. The pH change could be mitigated by reducing the sample channel electric field and/or increasing salt concentration in the buffer.

Development of a low flow‐resistive charged nanoporous membrane in a microchip for fast electropreconcentration

“…After the preconcentration reaches a saturated concentration, the preconcentrated sample plug size however, continues to increase, maintaining a constant sample collecting rate. This phenomenon is consistent with previously reported results [2,11,23,30]. A discontinuity point for the 1 M sample at 3 min (Fig.…”

“…Glass microchip fabrication and channel coating procedures are based on previous work (see Supporting Information, Chip fabrication). Briefly, chrome/photoresist coated 10 × 10 cm 2 , 0.9 mm thick B270 glass (Telic, Valencia, CA) was used as the base substrate.…”

“…Glass microchip fabrication and channel coating procedures are based on previous work [1,30] . The microchannels were filled with the dilute TMSMA solution for 3 min, and then washed with ethanol and dried.…”

Controllable pH Manipulations in Micro/Nanofluidic Device Using Nanoscale Electrokinetics

“…Previous literatures reported that the pH change could be mitigated by reducing the external electric field or increasing salt concentration in the buffer solution [40] and the surface area of electrodes [36]. To minimize pH changes in ICP device, other had demonstrated that continuous extraction of the pH changed fluid before biomolecules were blocked from passing through the ICP barrier [41].…”