Sampling, subsampling, and pipeting two-phase or three-phase samples may introduce
serious errors. Make and keep such samples homogeneous during transfer. Use special handling
to insure sample integrity when subsampling. Mix small samples with a magnetic stirrer. If
suspended solids are present, pipet with wide-bore pipets. If part of a sample adheres to the
sample container, consider this in evaluating and reporting results. Some samples dry with the
formation of a crust that prevents water evaporation; special handling is required to deal with
this. Avoid using a magnetic stirrer with samples containing magnetic particles.