Not at all. Seachem Purigen attracts organic compounds (detritus) from the water column. So although it can aid in water clarity, it does little to adsorb nitrates. Now Seachem advertises that the product removes organics before it breaks down and produces nitrates, but Im skeptical as I never found Purigen to have much impact on lowering tank nitrates. So Purigen can aid in water clarity, but IMO not really do much for nitrates - and frankly, I think polyeester fiber that you can get a big bag at WM for about $4 USD, works well and is more cost effective, (and recharging Purigen in a 50/50 bleach/water solution and then dechlorinating quickly gets old).
API's Nitra-Zorb (and other products like it) is a resin that somehow adsorbs ammonia and nitrates. It's rechargeable with ordinary salt water. I've put thousands of gallons through my modified tap water filter, recharging (soaking in salt water) every 200 gallons or so, and it's still going strong!
API Nitra-Zorb is only sold in pouches intended to be placed in filters to remove ammonia and nitrates. So when I first got the idea of putting Nitra-Zorb in the Tap Water Filter cartridge, I contacted API Tech support to see if they thought it would work. The Tech I spoke with said he simply didn't know as to his knowledge, the product had never been tested it that way. However, in the course of the dialog, he did mention that the product use life was reduced when detritus coated the resin...AH, but there is no detritus in fresh source water! So I gave it a shot with great success! (Necessity and inspiration - the parents of invention).
Bttw, in case anyone is wondering, other than a hobbyist/consumer, I have no affiliation with API.