Devices, methods and systems are provided for reducing the sample volume required for analysis. Inserts placed within a sample container, and substitute sample containers having smaller volume sample chambers are provided. Methods are provided for detection and quantification of target substances in reduced volume samples. Methods include placing a small-volume of sample in a small-volume insert. Methods include diluting a small-volume sample, and placing the diluted sample in a small-volume insert. Methods include reducing the volume of sample, and: increasing illumination; increasing dye concentration or amount; increasing the amount of an enzyme substrate; increasing the amounts, concentration, or labeling of antibodies for detection; increasing optical detector sensitivity; increasing the path length of light passing through the sample; decreasing the separation between sample and detector; altering the wavelength, or polarization, or number of wavelengths, passing through the sample; increasing electronic amplification of electrical signals; altering assay temperature; and other alterations.