Veratox HS for Ochratoxin is a competitive direct enzyme-linked immunosorbent assay (CD-ELISA) which allows the user to obtain exact concentrations in parts per billion (ppb). Free ochratoxin in the samples and controls is allowed to compete with enzyme-labeled ochratoxin (conjugate) for the antibody binding sites. After a wash step, substrate is added which reacts with the bound conjugate to produce blue color. More blue color means less ochratoxin. The test is read in a microwell reader to yield optical densities. The optical densities of the controls form the standard curve, and the sample optical densities are plotted against the curve to calculate the exact concentration of ochratoxin.