A novel gel permeation chromatography (GPC) method for the characterisation of nylon has been developed by researchers at Malvern Instruments (Malvern / UK; www.malvern.com). The technique is said to reduce significantly the cost of analysis, while also improving safety.

GPC is routinely used to determine the molecular weight and molecular weight distribution of polyamide, as it is, also, for many other polymers. The method relies on the complete dissolution of the polymer in a suitable solvent, which can be a challenge with sparingly soluble polymers. The solvent hexafluoroisopropanol (HFIPA) is conventionally used for nylon, even though it is relatively expensive and aggressively corrosive, with poor health and safety characteristics. In the new Malvern technique, the HFIPA solvent is replaced by formic acid, which usually costs only about 1% of the price of HFIPA and has a more favourable health and safety profile.

The new Malvern method was developed by Wei Sen Wong and Kyle Williams at the company’s research facility in Houston, Texas / USA. They found that formic acid achieves complete dissolution of nylon polymers and can also handle residual water from the polymerisation process. In addition, the technique does not require the addition of corrosive salts (such as potassium trifluoroacetate), thereby providing a further benefit by reducing wear and tear on the chromatography system.