A TECHNIQUE FOR THE MEASUREMENT OF TOTAL AMMONIA IN SMALL VOLUMES OF SEAWATER AND HEMOLYMPH

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 mul) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solutions in the range 1.0-50.0 mumol ammonia l-1 (n = 8), and with saline ammonia standard solutions in the range 5.0-50.0 mumol ammonia l-1 (n = 6) gave linear calibration curves (r = 0.999 in each case) with precision in the range 0.2-3.0%. Precision of measurement of ammonia in samples of seawater and diluted haemolymph was 0.9-3.3% (n = 11-13). The lower limit of detection is 0.20 mumol ammonia l-1. Thirty determinations can be made per hour.