A rapid,highly sensitive technique for the determination of ammonia in seawater

A reliable and sensitive technique for the rapid determination of ammonia in seawater is described. The procedure is based on the conversion of NH ₄ ⁺ in seawater to NH₃ and the subsequent diffusion of NH₃ across a hydrophobic membrane using flow-injection analysis. Sixty determinations can be made per hour on a flowing stream of seawater or discrete samples. The lower limit of detection is 0.05 M. Results of two applications that demonstrate the potential of this technique are presented, a laboratory excretion experiment employing the crabPachygrapsus crassipes, and small-scale vertical mapping of ammonia in the ocean.