Recording temporal characteristics of convection currents by continuous and segmented-flow sampling

Abstract

Despite the fact that the natural distribution of chemical substances in the three-dimensional world is far from homogeneous, most liquid-phase chemistry involves operations on homogeneous solutions. Here we describe two facile methods for real-time monitoring of liquid-phase chemical heterogeneity induced by convection in millilitre-range volumes. The liquid medium was continuously aspirated from the vial (acting as a "convection chamber''), and driven to online detectors either using continuous or discontinuous (segmented) hydrodynamic flow. In one embodiment, after the initial passage through a flow-through optical detector, the sample was driven to an electrospray ion source-set in front of the orifice of an ion trap mass spectrometer. The system recorded the emergence of chemical waves produced as a result of convection currents from the test substances introduced to the vial. Both variants of the method (using continuous and segmented flow) revealed fluctuations of the analyte concentration before an equilibrium was reached, and the mixture became homogeneous. We believe that this analytical scheme can further be used to study spatiotemporal characteristics of various dynamic chemical systems in liquid phase.