Using IAPSO Standard Seawater

IAPSO Standard Seawater is now only available in bottles. The ampoules were phased out during 2002 and should not still be in use.

  • Thoroughly shake bottle before opening
  • To open bottle simply remove metal crimp cap and take out stopper
  • Use the standard immediately after opening

    Salinometer standardisation with Standard Seawater should be made regularly during analysis runs to monitor machine drift. The frequency of standardisation depends on individual machine stability and the level of accuracy required. As an absolute minimum, standards should be measured at the beginning and end of each sample set.


    We recommend that Standard Seawater be stored at a temperature between 8 and 25°C.  It is advisable to avoid extremes of temperature, particularly freezing, as this can lead to precipitation of salts which will not readily dissolve on thawing.


    Our laboratory studies have shown that IAPSO Standard Seawater, in bottles, remains in calibration for at least three years after the calibration date. Culkin & Ridout (1998) showed changes equivalent to less than 0.001 in salinity in the label value, for these new-style borosilicate bottles, after 158 weeks storage. The older style soda glass ampoules stayed within specification for at least 18 months which was the time-limit of the experiments.


As well as the 35 salinity seawater (P-Series), additional standard seawaters are available with salinities of 38 (38H-Series), 30 (30L-Series) and 10 (10L-Series). These are used in conjunction with normal Standard Seawater (P-Series) to provide additional calibration points which can improve accuracy on high and low salinity samples.


Culkin, F. and Ridout, P.S. (1998), Stability of IAPSO Standard Seawater, j.atmos. & oceanic tech., 15, 1072-1075