by test kit from drug store, what do you mean exactly? The urine drug test kits? I'm pretty sure those test for the metabolites you body excretes out through urine, after it has broken down the original drug. But even if it did work, it won't tell you if you have alprazolam or another benzodiazepine.
I would think you'd need marquis or some type of reagent testing, but I'm only speculative at best. Although now that I am curious and have nothing else planned, I might look further into it. Will report back if I find anything useful.
Edit: So, not sure if marquis is the reagent you need, but I am under the impression that there will be one out there that suits your needs. Check the wiki article
on Reagent Testing, it has a nice list of the different reagents and the known reactions with various drugs. No benzos on there, but they do link to
Dancesafe(wiki article) who supposedly distributes the test kits for free. I would think contacting them would give you a pretty good lead on info at least.
Pill report on alprazolam powder that shows 3 different reagent reactions.
Edit2: Apparently alprazolam doesn't react with marquis, meckle, or mandelin.
Test kit for benzos - I have no idea about the reliability.
Another test kit for benzos, but says not for alprazolam. - you could theoretically use this to determine if it's another known benzo instead of alprazolam though.
Final Edit:
Here is a much more informative BL thread about the topic.
So there's this new benzo reagent available now, so we can finally start differentiating benzos. Yay. (not a shill) http://cgibin.wix.com/usdto#!shop/c172r
www.bluelight.org