Definitions

Process Analytical Technology (PAT) as defined by the United States Food and Drug Administration is a system for designing, analyzing, and controlling pharmaceutical manufacturing processes. This is done by taking measurements, during processing, of Critical Quality Attributes (CQA) of raw and in-process materials and processes to ensure product quality.

Dispersion: a mixture of more than one phase in which fine particles of one phase are distributed throughout another continuous phase. Dispersions are also referred to as suspensions, colloids, or solutions. A colloidal dispersion is made up of very fine particles in another substance called a dispersion medium such as an oil-in-water emulsion or even dust in the air.

Avalanche photodiodes (APDs) are semiconductor-based high-speed, high sensitivity photodetectors that use an internal gain mechanism that functions by applying a high reverse bias voltage. APDs are ideal for low light detection in the 200 to 1150nm range.

UPS- Chapter 788 of the United States Pharmacopeia devoted to practices and methods used to measure particle size and concentration in injectable liquids. This chapter aims to evaluate and determine the amount of particle contamination in parenteral products. The two primary methods for analysis are light obscuration and the microscope particle count test.

Zeta Potential (z) is the electric potential at the shear plane of a particle. Particles within a colloidal dispersion carry charges that contribute to the net charge of a particle. Each particle is surrounded by oppositely charged ions in what is called a fixed or stern layer. Beyond the fixed layer there are both positive and negative ions in what can be considered a charge “cloud”. These along with the ions in the stern layer form the electrical double layer at the particle-liquid interface. The ions within the charge cloud or “diffuse” region move about freely becoming less and less further away from the particle and eventually decay to zero. The potential at the boundary of the stern plane and the diffuse (shear) plane is known as the zeta potential.