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. Author manuscript; available in PMC: 2017 Mar 25.
Published in final edited form as: J Chromatogr A. 2015 Oct 26;1439:112–123. doi: 10.1016/j.chroma.2015.10.057

Figure 8.

Figure 8

DNA digests were enriched on the HPLC chip by online SPE. Here the washing time (and volume) is varied to determine the effect on analyte signal. Flow rate is 4 μL/min with 30% methanol in water containing 0.1% acetic acid. Data show that the analyte begins to elute (to waste) after 6 minutes (24 μL) or more of enrichment. Note the enrichment column has a volume of 40 nL, therefore 6 minutes of washing equals 600 column volumes. Also note that the separation gradient was started after enrichment, therefore the increasing retention time observed is artificial (BaP-dG elutes at 45% B in each case).