Electrical Sensing Zone / Microfluidic Resistive Pulse Sensing
Method Introduction
Electrical Sensing Zone (ESZ), also known as (microfluidic) resistive pulse sensing ((M)RPS), is a non-light-based technique for sizing and counting particles in the nm- and µm-size range.
ESZ/MRPS works by applying an electrical field between opposite sides of an orifice. Particles suspended in a conductive electrolyte solution are aspirated through the orifice and, upon passage, increase the electrical resistance proportional to the volume of their non-conductive part (Coulter principle). Size determination is based on calibration with spherical sizing standards and provides an equivalent spherical diameter of the analyzed particles. Depending on the system and setup, particles from about 50 nm up to 1 mm can be measured.
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Applications
On the one hand, ESZ/MRPS is used as an early research tool in combination with nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS). When measuring in this low size range, the most significant benefit is the need for very low sample volumes of only a few µL. On the other hand, ESZ/MRPS is used as an orthogonal technique to validate results from light-based particle characterization techniques in the nanometer and visible size range, such as flow imaging microscopy (FIM) and light obscuration (LO). The need for large sample volumes in the upper size range restricts the technique’s application during formulation development and stability studies.
ESZ/MRPS additionally requires a minimum sample conductivity, which in some instances requires the addition of electrolytes. ESZ/MRPS is suitable for analyzing protein aggregates, particles and colloidal systems, such as virus-like particles and polymers.
Quality and Biosafety Level
We provide all our analytical services with the highest quality standards. Experienced scientists carry out each project, and a scientific reviewer comprehensively checks every report or data presentation.
We offer this technology with the following quality and biosafety levels:
R&D level
We offer this method under R&D. Our GRP system assures the highest-quality research standards.
Up to biosafety level 1
This method can be applied to proteins, nucleic acids, and most viral vectors, including AAVs and more.
Analytical Method Development, Qualification and Validation
For common sample types, we can often apply standardized methods with little setup effort. However, when needed, our experienced analytical experts create or optimize custom methods tailored to your active pharmaceutical ingredient, product type and development phase.
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