Deblocking solutions, used for the cleavage of the 5‘-DMTr group at the last building block of nucleotide chain, can consist either of dichloroacetic or trichloroacetic acid in dichloromethane or toluene. Our Hyacinth Deblocking solution (3 % dichloroacetic acid in toluene at < 30 ppm water) is applicable for the syntheses of high quality, large scale oligonucleotides.