A technique for the measurement of total ammonia in small volumes of seawater and haemolymph

A rapid and precise technique combining flow-injection analysis and gas-diffusion is described for the measurement of total ammonia (NH3 + NH4 +) in small volumes (100–450 μl) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solutions in the range 1.0–50.0 μmol ammonia l-1 (n=8), and with saline ammonia standard solutions in the range 5.0–50.0 μmol ammonia l-1 (n=6)gave linear calibration curves (r=O.999 in each case) with precision in the range 0.2–3.0%. Precision of measurement of ammoniain samples of seawater and diluted haemolymph was 0.9–3.3% (n=11–13). The lower limit of detection is 0.20 μmol ammonia l-1. Thirty determinations can be made per hour.