(174at) Near Real-Time Urinary Chloride Monitoring in Cardiac Patients By Measuring Chloride Differential Adsorption and Reaction

Cardiac patients with congestive heart failure are routinely prescribed diuretics that increase urine output leading to the removal of sodium, chloride and water, reducing the patient’s fluid volume. However, diuretic use must be thoroughly monitored due to the risk of electrolyte imbalances, such as changes in chloride levels, that can lead to serious health issues. Current clinical methods to analyze electrolyte levels are expensive, time intensive and requires trained staff to perform the test. Thus, there is a significant demand for a rapid and affordable solution that ensures consistent tracking of electrolyte concentrations. We have developed a method using an electrochemical technique to determine the chloride concentration in urine samples¹. Our approach uses chronopotentiometry on silver screen-printed electrodes by applying a steady current between the working and counter electrodes. The current initiates a faradaic reaction on the silver working electrode, causing chloride ions from the solution to react and form solid silver chloride. During chronopotentiometry, the resulting potential versus time curve contains an inflection point representing the moment of local chloride ion depletion. We analyze the curve using python code script to calculate the derivative of the plot with the peak of the derivative indicating the transition time. This transition time directly correlates to the concentration of chloride ions in the solution.

Using this method, we have investigated a wide range of current densities, from 60 A/m² to 960 A/m². Figure 1 shows chloride concentration of 75mM, 100mM and 200mM at the current density of 800 A/m². Through our optimization process, we identified two discrete current densities that address the relevant physiological range of chloride concentration in urine samples. For the calibration process, we used chloride-spiked distilled water containing sodium chloride and other salts, maintaining a pH of 5.9, an electrical conductivity of 0.4 to 3.5 S/m, and a temperature of 25°C. We also conducted tests with artificial urine to validate the process and mimic urine samples. The results show good agreement for predicting chloride ion concentrations in the physiological relevant concentration range. Following that we have conducted tests on clinical urine samples and demonstrated the agreement between the measured chloride concentration and the established clinical method. This innovative approach is a promising advance for monitoring electrolyte imbalances in cardiac patients. The real-time capability of the sensor to measure chloride levels at the point of care could prove transformative in managing diuretic therapy for these patients.

Reference: [1] Nelson, A. M.; Habibi, S.; DeLancey, J. O. L.; Ashton-Miller, J. A.; Burns, M. A. Electrochemical Sensing of Urinary Chloride Ion Concentration for Near Real-Time Monitoring. Biosensors 2023, 13 (3), 331. https://doi.org/10.3390/bios13030331.