The Dependence of Spontaneous Charge Generation in Water on its Flow Rate in a Flow-Based Analytical System

Abstract

Highly sensitive biosensor systems are particularly sensitive to the charge state of an analyte. This charge state can have either a positive (for instance, in case of increasing the efficiency of fishing of low-abundant proteins) or negative effect (for instance, in case of the appearance of charge jumps upon the injection of analyte solution into a measuring cell, what can cause undesirable parasitic signals). Previously, it was demonstrated that upon the pumping of analyte solution through polymeric communications of biosensors with a peristaltic pump at a low (~1 mL/min) flow rate, an accumulation of charge, transferred by the liquid drops from the feeding system into the measuring cell, is observed. At this point, the time dependence of charge accumulation has a linear-stepwise form. In the present study, the influence of the flow rate of water on the parameters of the time dependence of the accumulation of charge in such a system—including the influence on the stepwise charge accumulation—has been investigated. The measurements have been performed with a highly sensitive electrometer sensor at 38 °C, which corresponds to a pathological state of a human body. It has been found that a linear-stepwise time dependence of charge accumulation is observed in a wide range of water flow rates (V= 0.9 to 7.2 mL/min). At that point, upon increasing the flow rate with the transition from the drop-by-drop mode of water supply (0.9 mL/min) to the jet flow (7.2 mL/min), an increase in the absolute value of accumulated charge is observed, but the magnitude of the charge jumps does not change significantly. Thus, the amount of charge accumulated in the cell ambiguously depends on the water flow rate—i.e., this dependence can be non-linear. Accounting for the discovered phenomenon is important in the development of new, more accurate models describing physicochemical properties of aqueous solutions and hemodynamics. This effect should also be taken into account in the development of highly sensitive diagnostic systems intended for the detection of single biomarkers of pathologies in humans and crops, as well as in other living systems. In low-concentration systems, the occurrence of a charge can become a significant factor affecting the efficiency of detection of biomolecules and the reliability of the data obtained. The detection of biomolecules present in the solution at low concentrations is in high demand in medical diagnostics for the revelation of biomarkers at the early asymptomatic stage of various diseases, including aggressive forms of cancer.