Premium
An optimized and simplified method for analysing urea and ammonia in freshwater aquaculture systems
Author(s) -
Larsen Bodil K,
Dalsgaard Johanne,
Pedersen Per Bovbjerg
Publication year - 2015
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.12314
Subject(s) - urease , urea , ammonia , ammonia volatilization from urea , hydrolysis , chromatography , chemistry , biology , zoology , biochemistry
This study presents a simple urease method for analysis of ammonia and urea in freshwater aquaculture systems. Urea is hydrolysed into ammonia using urease followed by analysis of released ammonia using the salicylate‐hypochlorite method. The hydrolysis of urea is performed at room temperature and without addition of a buffer. A number of tests were performed on water samples obtained from a commercial rainbow trout farm to determine the optimal urease concentration and time for complete hydrolysis. One mL of water sample was spiked with 1.3 mL urea at three different concentrations: 50 μg L −1 , 100 μg L −1 and 200 μg L −1 urea‐N. In addition, five concentrations of urease were tested, ranging from 0.1 U mL −1 to 4 U mL −1 . Samples were hydrolysed for various time periods ranging from 5 to 120 min. A urease concentration of 0.4 UmL −1 and a hydrolysis period of 120 min gave the best results, with 99.6–101% recovery of urea‐N in samples spiked with 100 or 200 μg L −1 urea‐N. The level of accurate quantification of ammonia using the method is 50 μg L −1 NH 4 + ‐N, and the detection level is 5–10 μg L −1 NH 4 + ‐N.