Visa for dual citizen

I went to PRC 6 months ago on a single entry tourist L type using one passport. Now, I'm going back to PRC using my US passport. How would that affect my application. I am going on a cruise of the Yangtrze river and the cruise company says they could give me letter of invitation. Is it going to be a problem that I went there on one passport and go back there using another passport. Or should I just not mention my trip 6 months ago since I used a different passport.