Liquid–liquid extraction(LLE) is the most widely used method for the extraction of analytes from aqueous food samples. In LLE, the sample is distributed or partitioned between two immiscible solvents in which the analyte has different solubilities. The solution containing the analyte must be immiscible with the solvent used to extract the analyte. The main advantages of this method are the wide availability of solvents and the use of low-cost apparatus. However, low recoveries, limited selectivity, and time-consuming procedures limit LLE. A variety of microscale variants of LLE have been reported and food applications of these have been recently review.
When to use extraction?
There are a lot of different separation techniques. Some techniques (such as distillation) use heat to separate two components. Because of the heat, one of the components will evaporate, whereas the other one will remain behind. However, if your components are sensitive to heat, distillation is not suitable. In a lot of those cases extraction is a good alternative. Since a lot of food components (especially flavours) are heat sensitive, extraction is used quite often in the food industry. In order for extraction to work, you should have a component available that is good in ‘pulling’ out the molecules you’re looking for.
Liquid-liquid extraction theory
Liquid-liquid extraction isn’t just used in food. It is a very big topic within analytical chemistry. Analytical chemists often use extraction to isolate or concentration a component so it’s easier to analyze by them. There’s quite a lot of theory available on liquid-liquid extraction so we’ll dive into the topic a little deeper.