A new method for the recovery of ammonium from natural waters for measurement of 15N composition in isotope dilution experiments

Efforts to measure the rate of nitrogen recycling in natural waters have depended on estimates of ammonium production using the ¹⁵N isotope dilution method. This technique requires the removal of dissolved ammonium from the water sample for analysis of the ¹⁵N content. Steam distillation or micro-diffusion methods have been most commonly used, but these techniques are labor intensive and time consuming. We have attempted to simplify the measurement of the planktonic regeneration of ammonium by presenting a mercury precipitation technique which is simple, practical, and easily used at sea.