They are characters like any other so they can be detected like any other. The specifics will depend on exactly what database you're using and/or exactly where you want to do it, i.e. in the database itself or in a VB.NET application.
EDIT: Actually, I should qualify that any character that doesn't have a literal representation cannot be detected by comparing to a literal representation like other characters would, but they do still have an ASCII or Unicode value so they can be detected by comparing the ASCII or Unicode values of the characters in your text to specific values. Those specific values can be hard-coded by you or, in VB, you can use the appropriate fields of the ControlChars class.