New tags and an encoding strategy for combinatorial synthesis are described. Combinatorial libraries of short oligonucleotides attached to TentaGel beads were synthesised by a split-and-mix strategy using 5′-DMTr or 5′-Fmoc-protected nucleoside phosphoramidites. Trityl moieties with different masses were used to tag the nature and position of monomer units (bases) coupled at each step in the synthesis. Beads with a ...