Agilent Technologies of Palo Alto, Calif., has received US Patent No. 6,939,673, "Manufacture of arrays with reduced error impact." The patent describes methods and apparatus for synthesizing a plurality of compounds such as biopolymers on a surface. An error in the deposition may occur in one or more of the plurality of steps and a reagent for forming the chemical compounds is deposited on the surface of the support. A determination is made as to whether an error occurred in the depositing of the reagent.