As an analytical contract service lab, Particle Technology Labs specializes in nanotechnology testing services for clients from many different industries.  Submicron Particle Size Distribution testing and Zeta Potential testing are just some of the many services offered.

Nanotechnology is an emerging field encompassing the study, fabrication, and manipulation of materials around 1 to 100 nanometers in size, or a tenth of a micron and less. These materials, which are known as nanomaterials, have future implications in the pharmaceutical, biomaterial, and manufacturing fields, among others. With the increased use and study of nanomaterials comes a demand for instruments capable of analyzing submicron particles.

Nanoparticle Tracking Analysis

Particle Technology Labs currently has the capability to provide this service in-house using our NanoSight NS300, which is the first cGMP-certified instrument of its kind in the United States. The NanoSight NS300 utilizes Nanoparticle Tracking Analysis (NTA) technology, which is one of the first commercially available technologies allowing high-resolution particle size distribution on a number-weighted basis and concentration analyses of submicron particles.

NTA technology employs the following steps:

A highly focused laser passes through a liquid dispersion in a specially designed cell.

As the nanoparticles in the dispersion interact with the laser, they are observed as points of light moving under Brownian motion through a microscope.

The rate at which the particles move is a function of their diffusional rate, which is in turn a function of their size as given by the Stokes-Einstein equation.

By tracking the motion of each particle over a specified amount of time, the diffusional rate can be measured and the particle size calculated.

Since the cell is a known volume and the particles present are individually counted, an accurate particle concentration can be calculated simultaneously. 

ASTM E2834-12 describes this innovative technique and provides guidance for industry use.

Dynamic Light Scattering

Another option that PTL has for the analysis of submicron particles is through Dynamic Light Scattering (DLS).

DLS is a commonly-used term to describe a technique which measures the particle size and estimated distribution of submicron particulate systems on an intensity-weighted basis.  In addition, the terms Photon Correlation Spectroscopy (PCS) and Quasi-Elastic Light Scattering (QELS) have also been used historically to refer to the same analytical principle.  By any name, the technique is widely recognized throughout the pharmaceutical and industrial world reflected in the existence of several standards describing the technique (i.e. ISO 22412, ISO 13321, and ASTM E2490-09).

DLS requires particles approximately less than a micron in size to be homogenously suspended in a fluid (aqueous or organic).  A few examples of suitable systems could include:

aggregated proteins

pigment components


emulsion droplets suspended in a continuous phase

DLS technlogy employs the following steps:

The nano-dispersed system is placed into the optical path of a LASER. 

The LASER is then scattered upon interacting with the particles in the suspension, which are moving by Brownian motion. 

The scattered light is captured by a detector over the course of the analysis to determine the rate of diffusion (i.e. how fast the particles move within a system due to Brownian motion).

The average hydrodynamic particle size (referred to as the Z-Average) is calculated on an intensity-weighted basis using the Stokes-Einstein equation. 

In simple terms, small particles move/diffuse more rapidly than larger particles.  

While other reporting formats are available, the most widely accepted and recommended way to report results from DLS is on an intensity basis using the Z-Average along with the Polydispersity Index (PDI).  The PDI is an indicator of the “broadness” of the particle size distribution.  DLS technology also allows for the determination of the critical micelle concentration (CMC) for various surfactants.  In addition, a DLS instrument at PTL is capable of determining zeta potential in an aqueous suspension as well as isoelectric point determination (IEP).

Microfluidic Resistive Pulse Sensing (MRPS)

A third option for the analysis of submicron particles at PTL is Microfluidic Resistive Pulse Sensing or MRPS.

The Microfluidic Resistive Pulse Sensing (MRPS) instrument used at PTL to measure nanoparticles in suspension is based on the Coulter Principle also known as the Electric Sensing Zone technique. Simply stated, the Coulter Principle refers to the use of an electric field for counting and sizing particles suspended in a conducting liquid.

PTL utilizes microfluidic resistive pulse sensing technology from Spectradyne. The Spectradyne nCS1, a patented nanoparticle analyzer features a microfluidic cartridge. This cartridge allows the electrical detection of nanoparticles which are counted and sized at a high resolution as they pass one by one through a constricted flow path.  Particles in a conductive fluid pass through a nanoscale constriction (NC). A voltage is applied continuously across the two sides of the NC. As particles pass through, the voltage signal increases, due to the electrical resistance of the particle within the NC.  The voltage signal is proportional to the volume of the particle’s resistance based on Ohm’s Law. As the particle exits the NC, the voltage signal returns to constant levels.  Particles are measured individually, with no dependence on particle composition or optical properties.

Only 3 microliters of analyte are required for any material type including transparent/opaque as well as conducting/insulating, etc. The size range of measurement is from 50 nm to 2 μm diameter. The instrument also can determine the particle concentration of a nanosuspension in the range of approximately 107 to 1011 particles/mL.  

Applications for MRPS include active pharmaceutical ingredients (APIs), excipients, nanoemulsions, proteins, exosomes, virosomes, and their aggregates, as well as general nanoparticles including gold/silver, colloidal silicon dioxide, metal-oxide nanoparticles, etc.

Nanotechnology Instrumentation

Below is a list of the instruments with nanotechnology testing capabilities available at PTL.  Interested clients should contact us to discuss if your sample and project is appropriate for Nanoparticle Tracking Analysis (NTA) or Dynamic Light Scattering (DLS) analysis and how these analytical techniques can provide additional answers to your project.

NanoSight NS300 - Click here for typical sample report.

Malvern Panalytical Zetasizer Nano - Click here for typical sample report.

Nicomp 380/ZLS - Click here for typical sample report.

Spectradyne nCS1 - Report coming soon.

Click here to request a quote, or,  for more information about our services, please contact us.