Teíchophoresis-enabled electrokinetic sample preparation and detection of calcium in natural plant samples

We present a novel upstream electrokinetic sample preparation and liquid interfacial microfluidic method to pre-concentrate, detect and quantify the concentration of a charged species, such as calcium, from a natural plant sample. We employ a new electrokinetic phenomenon, termed as “Teíchophoresis” (TPE) to preconcentrate sample calcium ions (up to a 20X increase) against a conductive wall. Using microfluidic flow, we then continuously transport the pre-concentrated calcium to a hydrodynamically streamed interfacial sensing zone where we utilize the model fluorescent chelation reaction between calcium and Calcium Green-1 (CG1) to fluorescently quantify the calcium concentration. Using a combination of finite element analysis and finite difference numerical modelling, we model the kinetics of the CG1-calcium interfacial binding and predictably validate our TPE-driven concentration results. Finally, we demonstrate the applicability of our device for real world samples by determining the calcium concentration in a tree bark extract acquired from a southern live oak and confirm our concentration results using ICP-MS. [Display omitted] •The phenomenon of Teíchophoresis (TPE) was utilized to preconcentrate Calcium ions against a conductive boundary wall. This electrokinetic phenomenon is similar to isotachophoresis, but it does not require a leading electrolyte.•The model fluorescent chelation reaction between Calcium and Calcium Green-1 (CG1) was employed to fluorescently quantify the preconcentrated calcium ion.•This technique is capable of detecting micromolar range calcium concentrations in biological samples such as tree bark.