Capillary Electrophoresis: Old Concept Turned Smart - lab-on-a-chip Based Electrophoresis with Contactless Conductivity Detection for Automated Remote Water and Environmental Monitoring

C4D – capacitively coupled contactless conductivity detection is an old concept of a label-free detection. Combining this with lab-on-a-chip technology as a smart tool for the analysis of small molecules shows significant advantages for remote monitoring: No sample preparation required combined with portability.
While chip-based capillary electrophoresis has established itself as one of the fastest and convenient methods for the analysis of larger molecules in many biotechnological applications, the large and economically attractive field of analysis of food, water and environmental samples has not been addressed with the same intensity.
A fully integrated chip-based capillary electrophoresis system, aimed to continuously analyze water samples is realized as a compact portable system utilizing C4D as an alternative detection method compared to the commonly used detection based fluorescence. Typical target molecules such as small ionic species like Li+, Na+, K+, Mg+, Cl-, F-, NH4+, SO4-- or NO3-, were detected. Results from sample matrices like various beverages, water from heaters and environmental samples will be presented. Typical application scenarios include measurement of fertilizer supplies in greenhouses or vertical farms to support an efficient dosing and recycling of wastewater or the analysis of fertilizer pollution in reservoirs or fish farms which has a major impact on water quality. With the integration of a water draw channel, the automated setup can take samples from up to 2m water level. Within the device, the sample is guided into a microfluidic network for electrophoretic ion separation. For long term stability of the system, an additional buffer exchange is implemented, allowing the system to run for more than a month in a standalone fashion.
Fast analysis times of a few minutes to seconds, detection limits in the µM range, and the realization as portable system are characteristics as an ideal tool for on-site analytical tasks.