For any schedule C business, you are the business and the business is you. It's as if you have two wallets. You pay from one or the other, but its all your own money in the end. It's a very good practice to keep accounts separate, but it is not required. Your purchase is certainly a business asset.
However, deducting the interest as business interest depends on whether you can follow the tracing rules. Can you prove that some particular dollars of interest are from the business purchase, and are not from personal purchases? Can you fairly and accurately allocate the interest to business and personal items? The more you use the card, the harder it will be to fairly and accurately allocate the interest. (If you make a $1000 payment, whose to say if it should be applied first to the container or first to some personal expense?)
So at best, deducting the interest as a business expense will require good record keeping that allows you to fairly and accurately allocate a portion of the interest to the business. Depending on your finances, it might be impossible to do this fairly and then you can't deduct the interest.
As I said, making the payment to the credit card company is just taking money from one wallet instead of the other, it's all your money. To track this in QB, you would need to speak to someone on that forum.
