If you really need to use single quotes or double qoutes... then use them and stop worrying about search engines and more about your readers.
Optimizing your site as much as possible is important but getting to this level of detail... I think this implies a bit of obsession and means that you need to take a break and relax a bit more
Before asking, do a search... if you don't find the answer, then ask The purpose of this forum is to help others in the community, that's why it's called Sitepoint and not Linkpoint. SP Guidelines - No fluff.