Hi!

You can use ZnCl2, but only a tiny bit, not too much (unlike for sulfur). Maybe look through literature, how much people have used. Good luck!

Hi Tobias,

Another toxic additive would be sodium azide (NaN3)  which I have used successfully for the preservation of DOC in seawater samples. A concentration of between 0.2 and 1 % is quite effective at suppressing any microbial activity. For example, 1% can be made up as a [4:1] mixture of [seawater:5% NaN3 stock solution].

Alternatively, acidification to pH 2-3 using HCl (~ 1 ml of 35% HCl in 1 litre of seawater) or H3PO4 (5 ml of 50% H3PO4 in 1 litre of seawater) can be used successfully for the preservation of DOC,  DIC and carbon isotopic composition.

Finally, a preservation method is described in the attached paper which does not require the use of any chemical additives, only refrigeration or freezing---both seem to work equally well. The method consists of collecting and storing a seawater sample in a foil bag originally designed for sampling low molecular weight gases such as CO, CO2, CH4 or SF6. The paper also describes how this method allows the transfer of the seawater sample to the hydrolysis vessel used for the analysis of delta13C without exposing the sample to the atmosphere.

Hope this may be of help!

Hi Tobias,

previously I stumbled across this - in case you are not aware of it by now:

http://www.ocean-sci.net/11/947/2015/os-11-947-2015.pdf 

Cheers, Kerstin

Hi,

Have any of you heard of a good irradiation system for preserving seawater samples? Maybe there is such a thing on the market?

Cheers,

Marcin