Inverse Gas Chromatography

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Inverse Gas Chromatography (IGC) is a powerful, detailed chromatographic technique for determining the gas retention time of samples, which can be then converted into a retention volume. This is directly related to several physico-chemical properties of the solid (absorbent), including thermodynamic parameters such as surface energy or heat of sorption, and kinetic parameters, such as the diffusion constant or the activation energy of diffusion.

With the measurement of surface properties at different surface coverages, a surface heterogeneity profile of the sample can be produced. Understanding energy distributions is particularly useful at interface boundaries of formulations, as well as to distinguish subtle differences in the surface chemistry of samples. Interactions with the high-energy sites also allow the detection of very small differences between materials. For this reason, iGC has been used successfully in various cases for the investigation of batch-to-batch problems.

iGC-SEA

Applications & Properties Measured with Inverse Gas Chromatography

Measuring and monitoring the surface energy of powders, fibers, particulates and films is important for a wide range of industries including pharmaceuticals, minerals, biomaterials, personal care, and composites. Surface energy can help elucidate any surface changes with respect to unit operations including milling, granulation, mixing, spray-drying, and freeze-drying.

In addition, quantifying surface modification processes like plasma treating, waxing, silianization, oxygenation and annealing can be done through monitoring the surface energy of materials.

For any composite or blend, the interfacial adhesion is an important parameter related to the ultimate stability and quality of the composite/blend. In addition, the works of adhesion and cohesion can help better understand flow behaviour and the tendency for certain materials to agglomerate. Through surface energy measurements, the iGC-SEA can directly calculate thermodynamic works of adhesion and works of cohesion. These values can be measured on materials ranging from carbon fibers, natural fibers, filler materials, polymers, metals and powders.

The heat of sorption is related to the affinity of a gas/vapor to a surface. These values are important for catalysts, filtration media, flavors/fragrances, and food materials.

Measuring the diffusion coefficients for vapors into solids is important for a number of industries, including catalysts, porous materials, membranes, and filtration media. The iGC-SEA can rapidly measure the diffusion coefficients for a wide range of solvents and temperatures.

Specific surface area is typically described in units of m2/g and BET is the most common model for the calculation of surface area. One of the routine experiments carried out by the DVS is to calculate BET surface area of materials using organic vapors as probe molecules. The traditional BET determination includes nitrogen sorption under vacuum conditions. The DVS overcomes these limitations by using a range of organic probe molecules for sorption which can be carried out at ambient and varied temperatures as well as under ambient pressure or under vacuum. This has the advantage of calculating BET surface areas under real conditions, which is useful for material application.

Dynamic Vapor Sorption is a gravimetric technique used to measure the sorption properties of materials using water and organic vapors, used to characterise complex materials used in a range of industries.

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Pharmaceuticals

Personal Care

Chemicals

Environmental

Adhesives

Energy Storage

Food and Beverage

Biomaterials

Catalysis

Polymers/Plastics