Theanine is an amino acid in tea, which plays an important role in the quality and aroma of tea. The following are common detection methods of theanine:

1. High performance liquid chromatography (HPLC)

High performance liquid chromatography (HPLC) is the most widely used method to detect theanine. After tea samples were crushed and extracted, they were separated and quantitatively determined by HPLC.

2. Capillary electrophoresis

Capillary electrophoresis is an efficient and accurate separation technology, which can separate various amino acids in a short time. This method has high sensitivity and accuracy for the detection of theanine in tea.

3. Mass spectrometry analysis

Mass spectrometry is a highly sensitive and high-resolution analytical technique, which can accurately analyze theanine in tea. This method needs to separate and purify theanine in tea by chromatography and other methods, and then quantitatively analyze it by mass spectrometry.

4. Infrared spectroscopy

Infrared spectroscopy can quickly and non-destructively detect theanine in tea. By measuring the infrared spectrum of tea samples, the position, shape and intensity of theanine characteristic peaks were used for quantitative analysis.