Abstract
A detailed method for the analysis of dissolved free amino acids (DFAA) and ammonium by reverse phase high performance chromatography of fluorescent derivatives using commercial columns and guard columns is described in detail for the newcomer. The method is flexible enough to allow for minor differences between different HPLC pump and gradient systems. For DFAA, the method is sensitive and reproducible down to high femptomole/low picomole levels, suitable for analysis of DFAA in natural waters down to the low nanomolar range. Aspects of reproducibility, sensitivity, sample preparation, cell extraction and sample storage are considered.