Dry basis

In analytical chemistry and related fields (e.g., food science, agriculture, environmental science), "dry basis" refers to expressing the quantity of a component in a sample as a percentage of the mass of the sample after all moisture has been removed. This contrasts with "wet basis" (or "as is" basis), where the quantity is expressed as a percentage of the original, undried sample mass.

The dry basis calculation is often used to standardize analytical results, allowing for more accurate comparisons between samples with varying moisture contents. This is because moisture content can significantly influence the apparent concentration of other components.

To convert a wet basis measurement to a dry basis measurement, the moisture content of the sample must be determined. The calculation is as follows:

Dry basis % = (Wet basis %) / (1 - Moisture content %)

Where moisture content is expressed as a decimal (e.g., 10% moisture = 0.10).

Dry basis reporting is crucial for accurately reflecting the composition of the solid matter within a sample, independent of its water content. This is particularly important when comparing the nutritional content of foods, the concentration of pollutants in soil, or the composition of other materials where moisture levels fluctuate.