Chicken Broth is one of those tricky items to find that are gluten free. You have to be careful of the various "flavours" that are included in the ingredient list.
I really like the Pacific Organic Chicken Broth - the sign at the grocery says states it is gluten free - and their website indicates the same. There is no explicit stamp on the box - but I've never had any problems with using it! You can get the low sodium version as well if you are looking for less salt. A complete listing of their products and allergens can be found here.
There is definity more chicken flavour than the Campbells Chicken Broth - and while it's more expensive (it's $3.99 a carton at the Sobeys in Newfoundland) - it's well worth it!
There's nothing like chicken soup on a cold winter day!