Would it be possible to do this among a group of 10 tags using a single reader?
It depends on what you mean by “detect.” If you just want to know that a tag is there, then you could use software to enter a specific ID for that tag, and the reader would interrogate all 10 tags and report back that the one you wanted was present. Most passive low-frequency (LF), high-frequency (HF) and ultrahigh-frequency (UHF) readers come with a software interface that would enable you to do this, and if you were using a more sophisticated application, it would certainly allow you to do so.
If you want to be able to pinpoint which of 10 passive UHF tags is the one you seek, then you might need to employ a handheld reader with a “Geiger counter” feature. Many handhelds can provide you with a visual and/or audio indication of your proximity to a specific tagged item. The unit would become louder or signal more frequently as you got closer to the correct tag.
—Mark Roberti, Founder and Editor, RFID Journal