Purity analysis is a laboratory or visual examination that determines the proportion of the declared product in a lot relative to other plant material, foreign varieties or foreign matter, and is standard for grains, pulses, seeds and herbs.
In trade practice
For grains and pulses, purity is assessed by sieving and hand-sorting a representative sub-sample, then weighing the separated fractions; results are expressed as a percentage of the declared species. For herbs and spices, botanical identification under a microscope may be required to distinguish the declared plant from adulterants. In honey trade, pollen analysis serves as a proxy for botanical purity. Laboratories should follow a named standard method, as results from different protocols are not directly comparable.
In a specification
A specification typically states a minimum purity percentage for the declared species and a maximum allowance for other plant material and foreign matter, with the sampling and analytical method referenced by name.