The column is provided for carrying out an isotope exchange between a liquid substance and a gaseous substance using a catalytic reaction. The present invention further provides methods for comparison of the methylation status of specific CpG dinucleotides, and patterns thereof between normal and diseased genomic DNA sequences, along with methods for determining all potentially methylatable CpG dinucleotides in a genomic DNA sample. The GDU meter compares the GDUs accumulated year to date to the average GDUs accumulated in previous years at the same site and calculates how much the year to date GDUs are above or below the historical GDUs.