Measurement of deoxyguanosine/thymidine ratios in complex mixtures by high-performance liquid chromatography for determination of the mole percentage guanine + cytosine of DNA.

The ratio of deoxyguanosine and thymidine can be determined in a complex mixture containing the major ribonucleosides and deoxynucleosides, the minor deoxynucleosides, and the nucleotide monophosphates by high-performance liquid chromatography. The isocratic procedure utilizes a C18 column and a solvent of methanol-triethylamine phosphate (pH 5.1). A single analysis requires 15 min. Within the range of 0.5-1.5 micrograms of total deoxynucleosides per sample, the determination is very precise and the relative standard deviation is about 0.1%. From the deoxyguanosine/thymidine ratio, a precise determination of the mole percentage guanine + cytosine of double-stranded DNA is calculated.