Improved analysis for “particulate” organic carbon and nitrogen from seawater1

Modifications are described to the Hewlett‐Packard model 185B CHN analyzer. “Particulate” organic carbon and nitrogen on 24‐mm‐diam GFC filters can easily be run simultaneously with the modified analyzer. With appropriate blank controls, the practical lower limits for analysis are about 5 µ g C and 1 µ g N. Thus it is possible to filter 1 liter or less for all seawater samples other than deep oceanic ones where up to 5 liters would probably be preferable.