The Zetasizer Nano ZS incorporates three techniques in a single compact unit:
- Dynamic Light Scattering (DLS) is used to measure particle and molecule size. This technique measures the diffusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship. Measurement of size as a function of concentration enables the calculation of kD, the DLS interaction parameter.
- Laser Doppler Micro-electrophoresis is used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which then move with a velocity related to their zeta potential. An available surface zeta potential accessory uses tracer particles to measure electro-osmosis close to a sample surface to calculate the zeta potential of the surface.
- Static Light Scattering is used to determine the molecular weight of proteins and polymers. In this technique, the scattering intensity of a number of concentrations of the sample is measured, and used to construct a Debye plot. From this the average molecular weight and second virial coefficient A2 can be calculated, which gives a measure of molecule solubility.
Particle size and molecular size
- Measurement range: 0.3 nm – 10.0 µm (diameter)
- Minimum sample volume: 12 µL
- Sensitivity: 0.1 mg/mL (Lysozyme)
- Measurement range: 3.8 nm – 100 µm (diameter)
- Minimum sample volume: 150 µL (20 µL using diffusion barrier method)
- Sensitivity: 10 mg/mL (BSA)
- Measurement range: 980Da – 20M Da*
- Minimum sample volume: 12µL (3-5 sample concentrations required)
- Accuracy: +/- 10% typical
- Temperature control range: 0°C – 90°C +/-0.1
- Light source: He-Ne laser 633nm
- Laser safety: Class 1