Refractive Index Measurement of Ionic Liquids
Ionic liquids are special designer solvents as they are nonvolatile and liquid at ambient temperature, leading to a wide range of applications. Their refractive index helps to control the quality and also to characterize them.
Ionic liquids - the special designer solvents
Ionic liquids are organic salts that are liquid at ambient temperatures. As their name already indicates, these liquids primarily consist of ions: positively charged cations and negatively charged anions. In contrast to normal inorganic salts, these fluids have a large, asymmetrical cation and a small anion, leading to special features, that these fluids are liquid at temperatures below 100 °C and nonvolatile. As different cations and anions can be combined, leading to many different properties, ionic liquids are often referred to as designer solvents and have a wide field of applications.
Some examples of their applications are in synthesis, catalysis, separation, electrochemistry, electro-lytes, lubrication, biomass processing, drug delivery and polymer chemistry as well as research.
Apart from the quality control of ionic liquids, the refractive index can be used to further characterize these fluids and to compare chemically similar groups of ionic liquids.
The Abbemat refractometer family from Anton Paar
The Abbemat refractometer family is ideal for determining the quality of ionic liquids as well as char-acterizing them with an accuracy of up to ±0.00002 nD. They are fully automatic and therefore us-er-independent. The measurement process is very easy and can be done within seconds. Only a small volume of liquid needs to be put onto the prism: Either manually via pipette or automatically via a sample changer.
As the refractive index is temperature-dependent, all Abbemat refractometers have internal Peltier temperature control. On top of that, special Abbemat refractometers for measuring at temperatures of up to 110 °C and at wavelengths different from 589.3 nm are available.