Particle Technology Labs services

Laser Diffraction, also known as Static Light Scattering, has become one of the most widely used particle sizing distribution techniques across various industries. Samples can be analyzed on either a liquid suspension or dry dispersion basis. The sample material is passed through a laser beam which results in the laser light scattered at a wide range of angles. Detectors placed at fixed angles measure the intensity of light scattered at that position. A mathematical model (Mie or Fraunhoffer Theory) is then applied to generate a particle size distribution. The final result is reported on an Equivalent Spherical Diameter Volume basis.

Electric Sensing Zone is also referred to as the Coulter Technique or Coulter Counter. The instrument is a true high resolution, high speed particle counter and particle size distribution analyzer that covers a nominal span of about 1.0 um to 300um. Under special circumstances, the lower detection level can be reduced to about 0.4 um. Data is typically presented to our clients on a Frequency (Population) and Volume (Mass) basis vs. Size. Being a true particle counter, the instrument can also be used to determine the concentration of Particles/mL of Fluid vs. Size.

Light Obscuration, also referred to as Photozone and Single Particle Optical Sensing (SPOS), is an analytical technique of high resolution capable of detecting a small percentage of outliers. It can also be used to obtain an overall size distribution, when operated with proper technique. An important consideration when choosing Light Obscuration is the concentration of the sample presented to the instrument. The sample must be in a dilute form (either as received or prepared by PTL) for analysis. The technology works by passing a dilute stream of particles in a liquid suspension between a light source and a detector. The light source in this case is a laser diode, which illuminates the individual particles in the stream and results in a shadow or blockage of light on the detector. This light blockage is termed obscuration.

Dynamic Light Scattering (DLS) is a commonly used term to describe a technique which measures the particle size and estimated distribution of submicron particulate systems. 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).

Image Analysis is a powerful analytical technique which can provide additional information on a sample compared to just “particle size” and distribution.  The majority of particle sizing techniques assume an equivalent spherical diameter of some measured property. This simplification is advantageous as a sphere is the only shape which can be described using a single number (i.e diameter). This assumption is acceptable in many applications where a comparison between samples is needed. In real world applications, particles are seldom spherical and cannot truly be described with a single number. The additional parameters provided by image analysis can help provide further insight into important properties which can affect dissolution, flowability, processing differences and material handling issues of a sample.

Sieving has been around since the time of the Egyptians and can be considered the backbone of particle size technology. Sieving’s continuing popularity is due to the technique’s fundamentally simple principle and methodology, historical reference, and cost effectiveness. Several instrument components involved in a sieve analysis can be quality controlled, making the technique applicable to various industries including pharmaceutical, industrial, agricultural, and chemical.

Mercury porosimetry is a powerful technique utilized for the evaluation of porosity, pore size distribution, and pore volume (among others) to characterize a wide variety of solid and powder materials. The instrument, known as a porosimeter, employs a pressurized chamber to force mercury to intrude into the voids in a porous substrate. As pressure is applied, mercury fills the larger pores first. As pressure increases, the filling proceeds to smaller and smaller pores. Both the inter-particle pores (between the individual particles) and the intra-particle pores (within the particle itself) can be characterized using this technique.

Porosity of materials with mesopores (pore diameters between 2-50 nm) is most commonly determined by gas physisorption.  Pore size distribution, pore volume, and area can be derived from the adsorption data using an appropriate mathematical model.  Although the technique can be used to evaluate samples of up to 300 nm, porosity characterization using this method is best for pores between 2-100 nm and in cases where Types II or IV isotherms are obtained.  The technique is referenced by several standard organizations such as ISO, USP, and ASTM.