Pasteurization as an alternative method for preservation of nitrate and nitrite in seawater samples

The first application of pasteurization to stabilize seawater samples for subsequent nitrate and nitrite determination in marine water is presented. Coastal seawater sampled from winter to late spring, with various chemical characteristics, was used. Samples were filtered through 0.7 and 1 μm pore size membranes before being treated. Promising results were obtained since concentration changes in the samples did not exceed about 1–2% for both nutrients (i.e., an absolute change of 0.005 μmol l−1 for nitrite) over periods from 16 to 22 months. The efficiency of the treatment is shown by comparing the behaviour of treated samples to untreated ones. Although this stabilization method requires an oven for processing samples, it is advantageous in that it does not alter the samples by chemical additions and enables samples to be stored at room temperature for many months, without special equipment, before analysis.