Alkaloids being chemically heterogeneous, cannot be identified in plant extracts using a single chromatographic test. However, the following general procedure may be used for the preliminary detection of alkaloids in plant tissues.

1. Macerate the dried plant material in 10% acetic acid in methanol for about 4 hours, filter and concentrate to 1/4^th the original volume.
2. Add ammonia drop by drop for the precipitation of the alkaloid. Centrifuge the solution and carefully collect the precipitate.
3. Dissolve the precipitate in a few drops of ethanol and spot it on a Silica gel TLC plate.
4. Develop in methanol: ammonia (200:3) and spray with dragendroff’s reagent. Presence of alkaloids is indicated by the development of an orange red–coloured spot.

The presence of alkaloids may be confirmed by measuring the UV absorbance of a sample of the alkaloid dissolved in 0.1 M sulphuric acid. Typical maxima values range from 250–303 nm. Alkaloids with aromatic rings in their structures may absorb at longer wavelengths.