文摘
A direct comparison has been made for the measurement of total dissolved nitrogen (TDN) in seawater using high temperature combustion (HTC) instruments. A side-by-side comparison in one laboratory (Lewes exercise) was made with two hybrid total organic carbon (TOC) instruments linked to chemiluminescence detectors (CLD), a combined TOC total nitrogen (TN) instrument, and two stand-alone TN instruments. Later, a series of field samples was run in home laboratories of the participants (Homelab exercise) using four hybrid TOC–CLD systems, the combined TOC/TN instrument, and three stand-alone TN instruments. In the Lewes and Homelab exercises, samples were also run by the more established persulfate oxidation method. There was fairly good agreement (group precision) among all the HTC methods; average % CV of ±12.0 % for five nitrogen compounds and average % CV of ±7.7 % for five natural samples in the Lewes exercise and % CV of ±10.7 % for 14 field samples in the Homelab exercise. In both cases, the persulfate method values were similar to those of the HTC instruments.
