What would be a good split character for splitting concatenated base64 strings?

I have a number of base64 strings that I need to concate开发者_Python百科nate to send over HTTP.

Is there a good character to use to split the strings (I'm guessing a character that is invalid inside a base64 string).

-thanks for the help

---

Since base64 only contains characters, digits and + and /, anything else should do - how about a space, a comma (',') or a pipe symbol ('|') ?