Who wants to quantify molecular weights and sizes? The Solution is a surprisingly Broad assortment of individuals and companies. Molecular size and weight is most frequently utilized in identification of proteins, and in characterization of polymers. Molecular Weight is commonly measured in industries such as:
- Pharmaceutical industry
- Biotech research
- Medical analysis
- The food industry
- Petroleum and polymer industries
- Radius of gyration and Hydrodynamic radius
Molecules are not simple shapes – unlike the fairly compliant, mathematically-uncomplicated atom, which can be spherical, molecules are hard to define as a very simple shape. Hence two dimensions have become industry standards, and analytical tools are geared towards getting them; the radius of gyration, and the hydrodynamic radius.
Radius of gyration
Scientific instruments can be used to identify the middle of dimensions and mass of a molecule; this is its radius of gyration. It is measured directly with static light scattering; however this technique has limits at dimensions lower than 10-15nm, and for large molecules such as polysaccharides. Viscometers are the instrument which is most frequently used for determining radius of gyration, using the Flory-Fox equation.
This is a behavioral property of a material – a measurement of size based on how it moves, meaning it is far more helpful in industrial or practical settings.
Size exclusion chromatography
Size exclusion Paper Chromatography is the method by which scientists determine the molecular dimensions not the weight. Molecules are split in columns packed with porous materials, which could consist of glass beads, polystyrene gels, silica gel, etc. Bigger molecules elute more quickly through the columns, because the molecules cannot fit into as many distances. A concentration detector is placed in the base of the GPC columns to ascertain the quantity of substance of each size fraction. In conventional SEC/GPC systems, operators will need to pass standards that are known through the columns prior to the sample. By making a calibration curve of size versus elution time, particle size of unknown samples can be calculated. In more recent times, addition of other detection techniques like Static Light Scattering and the Intrinsic Viscosity sensor provide direct measurement of molecular size and weight so that conventional calibration techniques are not required.
Gel permeation chromatography
SEC is also commonly referred to by other names. When an aqueous solution is used to take the sample through the column, the procedure is often called Gel Filtration Chromatography, and the title Gel Permeation Chromatography is frequently used when solvents are utilized to carry the material in question during the packed columns.