In solid extracts solvents are completely removed which makes this more concentrated than either fluid extracts or tinctures. Solid extract strength is measured in units of grams of crude herb per grams of extract. So, for example, a 5:1 concentration uses five grams of herb to produce 1 gram of extract. Solid extracts have the greatest chemical stability and are the most economical form for most herbs.
Fluid extracts are produced by evaporating most of the solvent to yield 1:1 concentration of herb to solvent. A fluid extract if five times as strong as a tincture made from the same solution.
Tinctures are the least concentrated of the three, are prepared by soaking the herb in a solvent. Typical solvents are water and alcohol for a specific amount of time, after which the solution is pressed. The strength of a tincture is measured by its concentration. It contains five times as much solvent as herbal material making it the least economical form of herbal supplements.
Herbs should be thoroughly analyzed and tested during harvesting and manufacturing to ensure high quality. Here are several types of analysis that can be done.
Even in the best circumstances, organically grown herbs can unknowingly be contaminated by ground water. It is essential that they be screened for contamination including, heavy metals, microbes and pesticides.
It surprises many people to know that even experts can have a difficult time identifying herbs that belong to the same family. Because of this one way to ensure that the herb is what it is represented to be is through chemical testing.
The final step is to test the herb for potency. Soil quality, rainfall, climatic conditions and growing time all help in determining the final potency of the herb. Good manufacturing techniques require the verification of the potency for each batch. In the case of standardized extracts, care must be taken to analyze and verify the active compounds in each bottle.