I welcome you to our next instruction video which is now for taking a sample for water

isotopes.

Water isotopes might be a little bit misleading because water itself has no isotopes, it's

H2O, but of course the H2O molecule has hydrogen and oxygen and hydrogen and oxygen has isotopes

so we are taking samples for the Delta O18 and the DH2 isotope value for the analysis

in the laboratory.

This is either done today by laser absorption spectroscopy or by isotope ratio mass spectrometry

and for that we need to transfer around 10-20 ml of our water sample into the laboratory

and we have to avoid evaporation under all circumstances.

So secondary evaporation after filling our vial by a loose cap or a weak seal will corrupt

our samples and we will not get the correct stable isotope value of the oxygen and hydrogen.

So you have to choose a material and a vial type that effectively events any leakage or

evaporation.

Besides that, the material or some treatment is not necessary for taking samples for water

isotopes.

This is rather simple.

So imagine this is our water samples from the river behind me.

We have in this case a glass vial.

Glass effectively prevents any diffusion or whatever through the walls.

So if you have the choice or if you have the possibility to go for glass vials, take the glass vials.

If you are going to transport it later on by air cargo, glass might not be the perfect choice because it breaks easily.

Also sometimes if you put it into the fridge it might freeze.

It's not harmful for the stable isotopes if you freeze the samples for water isotopes.

However, it will probably break your glass vial.

Freezing is also not necessary for any preservation.

And then we have a cap here with a seal inside.

So in this case this is a butyl rubber scepter which we placed inside the cap.

And the butyl rubber makes an efficient seal with the glass and avoids any evaporation.

But in principle you can use any other vial type.

For example I've brought a small selection here.

You can use a crimp vial where you need this special crimp device with a thick butyl rubber scepter.

You put it on top and you crimp it, makes an efficient seal.

You can use an ex-detainer which also has a butyl rubber scepter inside.

Fill it up to the brim, close it, effectively sealed.

You can also go for plastic.

In terms of plastic I would strongly recommend for go for HDPE.

High density polyethylene, nothing else because it avoids evaporation or diffusion through the walls very effectively.

And do not use just a simple cap.

Use for example a cap like this one with a so called inner stopper which effectively prevents also any secondary evaporation from the wire.

The laboratory will need around 5 ml for the final analysis but to have a little bit of a buffer I recommend to take 10 or 20 ml of your water sample.

If you have your vial and your tightly sealing cap you simply take out your water sample either from the river or here from this beaker with a syringe.

You can pre-filter it with this disc filter which is 0.45 micrometers taking out the particulate organic matter.

Gently fill up your vial, you might pre-flush your vial if you want.

Fill it up until it's completely filled, no headspace, cap it, make sure the cap sits tightly.

This is your water sample for water-stabilizer top analysis, pretty simple and pretty much straightforward.

To avoid any secondary evaporation or to ensure that the cap got not removed during the transportation,

you can also put some of the parafilm wax foil around the cap to securely tighten it and to also make an additional seal around the most vulnerable part

which is of course the gap between the cap and the vial.

And with this we are at the end of the instruction video for taking samples for water-stable isotope analysis.