Methods are provided for preparing nucleic acid arrays on a support,
particularly substantially planar supports. In one group of these methods
a plurality of nucleic acids are synthesized on the support and the
synthesis steps include oxidizing a phosphite triester nucleic acid
linkage to a phosphate triester nucleic acid linkage using a solution
about 0.005 M to about 0.05 M iodine in a mixture comprising water and
organic solvent. In another group of these methods a plurality of nucleic
acids are synthesized on the support and the synthesis steps include
oxidizing a phosphite triester nucleic acid linkage to a phosphate
triester nucleic acid linkage using a solution comprising iodine and at
least 4% by volume of water.
