thermodynamics - In a reaction between Calcium Ammonium Nitrate or Urea with water, does Nitrogen Content and Purity affect how cold the solution gets?

Recently, I bought an ice pack that contained Calcium Ammonium Nitrate, and realized that it really didn't get cold. I came to the conclusion that perhaps Urea is more effective, yet it is still puzzling to me that in a perfectly secure ice pack, it got to refrigerator water temperature.

I was thinking, perhaps purity of compound and nitrogen content (46% in Urea vs ~23% in CAN) could make a difference.