Deep eutectic solvents (DES) are a new class of ionic liquids that provide an efficient, environmentally friendly alternative to conventionally used organic solvents. By using different combinations of starting components, we can control the physicochemical properties of the prepared DES, which is useful for extraction in the analysis of samples.
In this work, I prepared 4 DES using choline chloride as hydrogen bond acceptor and different hydrogen bond donors (lactic acid, butane-1,4-diol, glycerol, ethylene glycol). I have successfully synthesized all DES by using 3 different preparation procedures based on heating and stirring and different types of drying. I visually evaluated the stability of the prepared DES over a period of 50 days. Since DES is hygroscopic, I determined the content of absorbed water by Karl Fischer titration. I then characterized DES, which was prepared using dried choline chloride, for further use as an extraction solvent by FTIR and thermal analysis. Using FTIR spectroscopy, I observed hydrogen bonds in DES and the effects of adding water on existing hydrogen bonds and the formation of new hydrogen bonds. Using dynamic thermogravimetry, I evaluated the thermal stability of Tonset for prepared DES and DES with 25 % water added (w/w). I also determined the long-term thermal stability using isothermal thermogravimetry for 2 h at 60 and 80 °C.
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