To use HPLC peak area to determine OD260, a correlation graph between OD260 and HPLC peak area needs to be established first. ODN 1a is used to demonstrate the process. A solution of 1a from a 1 µmol synthesis was prepared (see Materials and Methods section). The concentration does not need to be known or accurate, but should be suitable for the generation of HPLC peaks with areas close to those in HPLC profiles a lab typically generates for ODN purification and analysis. For the case of 1a, the ODN from the 1 µmol synthesis was dissolved in 1 mL water. Various volumes as indicated in Table was injected into HPLC. For each injection, the ODN under the correct peak was collected and the area of the same peak was recorded (Table ). The ODN was evaporated to dryness, and dissolved in 1 mL of water. The value of OD260 was then obtained by measuring the absorbance using a UV spectrometer or a NanoDrop. Plotting the OD260 numbers against peak areas gave the required correlation graph (Figure ). As expected, the data fitted well with straight lines, and the two lines are very close. Their slopes are 0.00036 and 0.00038, respectively. The slight difference may come from the lower accuracy of NanoDrop measurements.