Rapid field test for alkaloids in plant material
Adapted from - Culvenor and Fitzgerald, J Pharm. Sci. #52:303-4, 1963.

 Starting with about 2-4 gms of plant material, preferably soft tissue like leaves etc.,  grind in a mortar and pestle with clean sand and chloroform to yield a thick slurry. 10 ml Ammoniacal chloroform (6.71 NH4OH in 993.29 chloroform, 0.10N) is added and macerated with the plant material. The chloroform is drawn off and filtered into a test tube. Dilute sulfuric acid (2N, 0.5-1ml) is added to the test tube and shaken, then allowed to separate from the chloroform layer.
The aqueous layer is removed with a pipette, with cotton wool over the end to act as a crude filter, and 2-3 drops are placed in a test tube.
On addition of Mayers reagent or Silicotungstic acid a precipitate will form with any alkaloids in the solution. The amount of precipitate can give a crude estimate of the relative quantitative amount of alkaloid present.
The final comments from the authors of the original paper.
"Our conclusion is that the field method with fresh material is a reliable screening procedure in so far no species are missed which would have attracted further attention on the basis of the laboratory method"

With practice, only a few minutes of work should be able to give rapid and useful testing of relative alkaloid content of various plant (or any biological) material. Different plant tissues will give different results, soft foliage such as leaves will evidently give better results through the easier breaking of tissues to release alkaloids than say bark.

See further discussion about using an extended method for relative quantitative analysis of different samples