How does riffling reduce sample size while keeping a sample representative?

In analytical chemistry, riffling is a method used to reduce the volume of a laboratory sample while ensuring the resulting test sample remains representative of the original material.1

The process works by pouring the ground and mixed sample through a set of riffles—typically a stationary arrangement of alternating chutes—which uniformly splits the material into two or more streams. Because the sample is divided into these equal streams, the portion selected for further processing maintains the same composition as the original bulk material.1

If the initial laboratory sample is very large, the riffling process can be repeated several times until the desired test sample size is achieved. While simple riffles use a stationary design, more advanced spinning rifflers utilize rotating carousels or feeders to further ensure the accuracy and representativeness of the split. This technique is essential for preparing particulate solids for chemical analysis, as it allows for precise size reduction without compromising the integrity of the sample.1