Why did the two of you bother even having and keeping separate checking accounts after you got married, unless you planned on squirreling some of your money away for just such a situation as the one you now are considering?
It doesn't matter if you have separate accounts. If the money was earned during the marriage, and spent on shared expenses during the marriage, one can easily argue that it's marital property - whether it's in an individual or joint account. Your wife can claim your personal account balances as marital property if she can show that the money deposited was earned during the course of the marriage, just as you can do the same with money she has in her own personal accounts.
Once you file for divorce, you'll BOTH be obligated to reveal both the existence and transaction records of all accounts you hold individually. You'll each have to prove when the money was obtained and how it was spent to determine how much can be counted as marital assets.