Is nitrogen from amino acid breakdown stored in the liver?

No, nitrogen from amino acid is not stored in the liver.

The nitrogen from amino acid breakdown is primarily converted into urea in the liver, through the process of ureagenesis. Urea is then transported to the kidneys and excreted in the urine. The liver does not store nitrogen in any significant amount. After proteins are broken down, the carbon skeletons of the amino acids are converted into energy or used for other metabolic purposes, while the nitrogen atoms are released as urea.