What would be a good split character to separate base64 concatenated strings?

Question

I have a number of base64 strings that I need to concatenate to send over HTTP.

Is there a good character to split the strings (I assume the character is not valid inside the base64 string).

-thanks for reference

Answer 1

Since base64 contains only characters, numbers, and + and /, something else needs to be done - how about a space, a comma (','), or a pipe character ('|')?