The matrix on a CoCRecord tells the laboratory and regulators what kind of sample was collected. For Piper's groundwater monitoring use case, the matrix is typically "groundwater," but it may also be "surface water," "sediment," or "soil" for sites with multi-media monitoring programs. The matrix determines which holding times apply, which preservation methods are required, and which regulatory standards the results are compared against when Piper checks for threshold exceedances. Always select the matrix that matches the actual medium sampled.
Technical section
Data model, API, and internals — visible to developers.