Abstract: Determination of Analytes in a Sample Matrix by Solvent Extraction A method for the assay of one or more analytes in a sample matrix comprising the steps of: performing analyte extraction on the sample matrix, said analyte extraction comprising combining the sample matrix with a solvent for an extraction period which is less than that required for reaching equilibrium; and separating the analyte containing solvent from the sample matrix; next measuring a level of analyte present in the separated solvent; and then applying in a computer a calibration by which is established a mathematical relationship between levels of analyte extracted from each of a plurality of reference samples by means of the process employed above in the extraction for the sample matrix and a reference value of the levels of analyte for each reference sample to thereby derive a measure of the level of analyte in the sample matrix.