260/280 and 260/230 are ratios commonly used in measurements to assess the purity of nucleic acid samples, and are determined by measuring the absorbance of light at specific wavelengths to provide information about the presence of contaminants or impurities in a sample. A pure DNA sample would have a 260/280 ratio ranging from approximately 1.7 - 2.0, and a 260/230 ratio ranging from approximately 2.0 - 2.2. Ratios lower than these ranges could indicate the presence of contaminants that have absorbances close to either 280nm or 230nm respectively.

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