Non-volatile residue (NVR) or non-volatile matter is the soluble, suspended, or particulate material remaining following evaporation of the volatile solvent which contains the material. Analysis of nonvolatile content can be used to determine the purity of a solvent as well as to measure the amount of micro-contamination on the surface of an item or component (i.e. its cleanliness).
NVR determination involves evaporating the organic solvent, then measuring the residue gravimetrically using a sensitive balance and carefully-tared weighing vessels. This type of analysis is fundamental in the fields of water quality and environmental testing, as well as in the chemical, pharmaceutical, medical device and electronic industries.
Determination of non-volatile matter is an important quality assurance test for products in which the presence of any residue may affect product quality and performance, or process efficiency. The NVR test is useful to control manufacturing processes and ensure compliance with specifications. For example:
- Ensuring cleanliness of medical equipment, especially for implantable medical devices
- Minimizing micro-contamination on the components of computer hard disk drives
- Measuring quality of products such as paint, varnish, lacquer and related products
- Upholding the limits for toxic solvent migration in plastic food packaging
Why Accurate Weighing is Important
Weighing non volatile residue is a differential weighing application. The amount of non volatile residue collected is typically very small. When the solvent is very pure, or when very little contamination is present, a large volume needs to be used to provide even a small quantity of the residue. Measurement of such small quantities requires a highly accurate balance; in many cases, the readability required is 10 or 1 µg (5-6 decimal places).