Elutriation is a materials separation method where smaller and larger materials are forced apart with the use of a column of liquid or gas. It can be used on the macro and micro level, from preparation of cell samples for analysis to separation of single stream recycling. Equipment for use in elutriation is available from a number of manufacturers and people can order custom equipment for unique applications. Such equipment tends to be more expensive than offerings on the conventional product lineup.
In elutriation, materials are fed into a rising column of separation medium. This can be something like a buffer solution or a jet of air. Small, light particles drift up in the column, while large, heavy particles sink down. This creates a series of layers of different materials of different sizes. In something like single stream recycling, large air jets are used for quick and basic separation, allowing plastic containers to go to one side of a processing facility, while glass lands on the other, for example, with metals being separated earlier in the process with the use of magnets.
In the lab, elutriation equipment is designed to work with very small particles in samples of blood, urine, and other materials. Lab technicians are concerned with contamination, as well as sorting, and must follow precise procedures when using the equipment to make sure samples do not come into contact with each other and cause false readings. Medical equipment for elutriation is usually designed to be easily sterilized between uses.
Another use for elutriation can be seen in the analysis of mineral samples, as seen when oceanographers want to research the composition of benthic clay or geologists want to evaluate the contents of mineral deposits. Samples are separated by size and density in the column, allowing people to generate a complete list of the materials present in the sample and to note their concentrations. People evaluating mineral deposits for commercial value are particularly concerned with concentrations; a site may contain diamonds, for example, but in such low amounts that they cannot be efficiently mined for sale.
Buffer mediums and gas mixtures for elutriation are available from scientific suppliers in cases where simple air or water will not be sufficient for a given task. Individual labs may also formulate their own, providing information about how to create the solution in the lab manual so technicians can be consistent by following the directions.