posted on 2017-04-12, 00:00authored byLisiqi Xie, Xiao Huang, Bin Su
A portable
amperometric ion sensor was fabricated by integrating
silica isoporous membrane (SIM) and organogel composed of polyvinyl
chloride and 1,2-dichloroethane (PVC-DCE) on a 3D-printed polymer
chip. The detection of ionic species in aqueous samples could be accomplished
by adding a microliter of sample droplet to the sensor and by identifying
the ion-transfer potential and current magnitude at the water/organogel
interface array templated by SIM. Thanks to the ultrasmall channel
size (2–3 nm in diameter), high channel density (4 × 108 μm–2), and ultrathin thickness (80
nm) of SIM, the ensemble of nanoscopic water/organogel (nano-W/Gel)
interface array behaved like a microinterface with two back-to-back
hemispherical mass diffusion zones. So, the heterogeneous ion-transfer
across the nano-W/Gel interface array generated a steady-state sigmoidal
current wave. The detection of choline (Ch) and its derivatives, including
acetylcholine (ACh), benzoylcholine (BCh), and atropine (AP), in aqueous
samples was examined with this portable sensor. Using differential
pulse stripping voltammetry (DPSV), the quantification of these analytes
was achieved with a limit of detection (LOD) down to 1 μM. Moreover,
the portable ion sensor was insensitive to various potential interferents
that might coexist in vivo, owing to size-/charge-based selectivity
and antifouling capacity of SIM. With this priority, the portable
ion sensor was able to quantitatively determine Ch and its derivatives
in diluted urine and blood samples. The LODs for Ch, ACh, AP, and
BCh in urine were 1.12, 1.30, 1.08, and 0.99 μM, and those for
blood samples were 3.61, 3.38, 2.32, and 1.81 μM, respectively.