TRPS technology uses the Coulter principle on the nanoscale. Voltage is applied across the nanopore via the silver-silver chloride (Ag/AgCl) electrodes in the fluid cell. When ions move between the electrodes through the nanopore, a baseline current is created. A temporary decrease in current is detected as particles pass though the nanopore which allows for size, concentration and zeta potential measurements of particles in electrolyte solution..
The below figure illustrates how TRPS works.
Sample particles are driven through the nanopore by applying a combination of pressure and voltage, and each particle causes a resistive pulse or "blockade" signal that is detected and measured by the application software.
- Blockade magnitude is directly proportional to the volume of each particle.
- Blockade frequency is used to determine particle concentration.
- Blockade duration changes with the velocity of the particle and can be used to calculate the surface charge and zeta potential of each particle.
Magnitude, frequency and duration values are converted into particle measurements by calibration with particles of known size, concentration and surface charge/zeta potential.