Dear Andy

It is a big problem.

I hope this information is useful for you.

http://www.aslo.org/lo/toc/vol_36/issue_2/0235.pdf

J. E. Sherwood, F. Stagnitti, M. J. Kokkinn, W. D. Williams. 1992. A standard table for predicting equilibrium dissolved oxygen concentrations in Salt Lakes dominated by sodium chloride. International Journal of Salt Lake Research, Vol 1: 1-6.

Best regards

Hi Andy! It think that probably Winkler method can give you good results. http://bats.bios.edu/methods/chapter6.pdf

Hi Andy,

I have used optodes for my PhD with pretty nice results.

Hope this paper helps you:

http://www.int-res.com/articles/ame_oa/a056p255.pdf

Cheers

Hey Andy! Well, if you are going for optodes for the measurement of oxygen in the hypersaline waters, i think u need some corrections in the final value as given in the Sherwood et al., 1992. But I am not sure! Regarding the optodes, I suggest to go for AANDERAA made optodes for measurements on field, it is handy and can give you perfect measurements insitu. I have used them quite a lot, they are reliable. for reference see some of my papers on respiration in the researchgate profile.

Hey!

I forgot to tell you. If you plan for AANDERAA optode/any other optode sensor/ any other good sensors, you can try them at 0% oxygen saturation and 100% oxygen saturation in the hypersaline water for several time (n = ca 10) to get a confirmation on their performance.

regards

I agree with Luigi Naselli-Flores and also suggest the old, but very good Winkler method.

Use the Miller method. A titration used for hypersaline waters - published in Limnology and Oceanography 15:814-815. Based on oxidation of ferrous ions, color change to clear from methylene blue indicator. Should work for you.

In our previous study in a hipersaline lake (salinity above 50 ‰) we measured DO with WTW oximeter and after EN ISO 5814. Good luck, Gana

Here I send a spreadsheet with correcion factors for salinity above 100 ppt.

From the following link:

www.deltaenvironmental.com.au

Good luck

The Miller method is more accurate than Winkler titration as the salinity rises.

Hi Andy! I agree with Luigi. Winkler method could be a good idea.

Hi Andy! We determined dissolved oxygen in seawater by using Thiosulfate-iodimetric method. I don't know Didi you try this method. It 's similar as the Winkler method. You can get the standard method in water quality measurement.

Hi Andy

What about using micro-electrodes as you find them at Unisense? - if you

have money for it

The first prototypes were developed and used under highly saline conditions -

so I believe the new ones would be working too

Check their homepage and send them a question - they are very helpfull ppl there

Good luck

Søren

Dear Andy,

Any electrochemical oxygen sensors, like Clark-type, should work without problems. You could use microsensors for instance. With the macrosensors there should be no problems neither. They have a membrane permeable to gases and not to ions, so it doesn't matter the salinity of the external medium. The solubility of the oxygen changes a lot with the salinity, so take the reading in percentage of saturation and transform it to concentration using the in situ temperature and salinity.

Regards

Emilio

Ivan, please explain your comment about optical probes.

Hi Ivan, I wonder why the optode (optical sensor) did not work for you! Top of that the optode (optical sensor) is already proven to be a good one in marine waters and is calibrated with the Winkler's method. AANDERAA optode works good. Please see the link below

https://www.researchgate.net/publication/235917679_Precise_continuous_measurements_of_pelagic_respiration_in_coastal_waters_with_Oxygen_Optodes?ev=prf_pub

Article Precise continuous measurements of pelagic respiration in co...

I read the paper and I still have the same question as Satya. I do not know a technical reason why the optical probe should not work in saline water. I was wondering if you had some insight to why this might be a problem. Or, as you mentioned in an earlier response, perhaps there was some other problem.

Dear Andy, Winkler method is reliable and cheap. We used it in hypersaline lakes.

I agree with the answers: to use titration and the Winkler method

Sven Erik Jørgensen

Hi, Ivan! Our laboratory use only Winkler-method, so I cannot compare.

Thanks everyone for the great advice!

In one of our study conducted in a lagoon lake, where the conductivity was mesured as 23000 mS/cm, we have determined the dissolved oxygen parameter without any problem by using HQ40D multiparameter device (Hach Lange) (with an outdoor oxygen probe). But we could not determine the COD parameter in the same water by using DR3800 Spectrofotometer (with LCK 414 for COD).

You will also need to monitor salinity as it displaces the oxygen. Some probes have this sensor and correction built in. I think optodes measure partial pressure of oxygen so do not recognise the salt has displaced much of the oxygen (partial pressure the same at different salinities, despite change in DO concentration). There must be a point at which salt displaces all oxygen, which may explain why some have recorded 0 values with optodes.