Malvern Zetasizer ZSP - dynamic light scattering (DLS) system
The Zetasizer Nano ZSP incorporates three techniques in a single compact unit, and has a range of options and accessories to optimize and simplify the measurement of different sample types.
Dynamic Light Scattering is used to measure particle and molecule size. DLS 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.
The Microrheology option uses the DLS measurement of tracer particles to probe the structure of dilute polymer and protein solutions.
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. This velocity is measured using a patented laser interferometric technique called M3-PALS (Phase analysis Light Scattering). This enables the calculation of electrophoretic mobility and from this the zeta potential and zeta potential distribution.
Static Light Scattering is used to determine the molecular weight of proteins and polymers. The scattering intensity of a number of concentrations of the sample is measured, and used to construct a Debye plot. From this the weight average molecular weight and second virial coefficient can be calculated, which provides a measure of protein solubility.
This technique is very demanding on the sensitivity and stability of the whole system, and requires that every element of the design is optimized to ensure accuracy and repeatability.
The software is designed to be versatile and rich in features without compromising ease of use. Standard Operating Procedures (SOP) simplify routine measurements, a quality factor gives a single place for confirmation of data quality, and an expert advice system is provided to assist with data interpretation.