I have always wondered why one would want to use completely degassed water. It makes no sense. You just need to remove large air nuclei (someone should calculate and measure which size class of air nuclei changes resistance). I think the main goal is to remove any large gas nuclei so that you are not introducing bubbles to bordered pit fields while perfusing, which may increase R. Since degassed water does not exist in the xylem system, using completely degassed water may even remove gas from the plant hydraulic system during perfusion since the water in the xylem should be in gas equilibrium with the surrounding tissue. Furthermore, I notice that many go through the pain of the degasding procedure, then pour the solution into a container which regasses it and then this solution sits for hours, sometimes longer, and thus allowing gas to diffuse back into the perfusion solution. With that being said, I use autoclved KCl solution, that I then put under vacuum using small amounts of solution at a time. Using a 60 cc hydraulic syringe i lock off the tip with a luer loc then pull back the plunger and agitate the system, repeat several times until the bubbling stops. Each time I push the air out, then relock it etc. Then i attach my syringe to the big hydraulic system and slowly push the fluid into the hydraulic head container that is closed in a plastic bag system (sort of like a baby bottle) to reduce contact with air. I am using a SSFM or pressure transducers to measure deltaP across a hydraulic resistor system. For me, I am really only concerned with having any bacteria and reducing the abundance of air nuclei as much as possible in my perfusion solution. Seems to work.

Hi J-C,

You can also bubbling helium through your solution for measuring K. This is what people that work on HPLC use to do since it is more effective than the vacuum, although a bit expensive too.    

the fastest method will boiling the water, and will be even faster ans more efficient if you pump (create partial dynamic vacuum) at the same time.

Hi J-C:

I agree with you! I have been trying bubbling He through the solution, but Argon is cheaper and works nicely.

Heating / warming and stirring - it does not need to boil - like Boris suggested warming in an ultrasonic bath would be even more effective!

I have never liked the idea of boiling water; it never removes all the air because a lot of air is soluble in hot water. This was the brainchild (boiling) of Dynamax and I tried to talk them out of it. They were just too cheap to supply vacuum pumps with my HPFMs. Also hot water re-saturates while cooling unless you exclude all air (seal off the bottle while it is filled with steam). No steam? Air gets back in. Check out if I'm right by using an 02 electrode! Helium might be a good idea for HPLC but never considered it for 'degassing'. Does O2 or N2 interfere with HPLC?? Anyway He is soluble in water. The Henry's law constant for He:N2:02 is in the ratio 3.7:6.1:13. It would clear out the 02 and N2 and saturate it with He, AND when flushing stems then N2 and O2 can be dissolved into the water BUT replaced with He. ALSO you have to bubble He thru a narrow neck bottle so that NO AIR is next to the water or you are doing nothing but adding He without removing 02 and N2. FINALLY: Noisy vacuum pumps. You can buy VERY VERY quite pumps from the UK supplier. We use several in our lab and they cause no problems. I can give you the make and model if your interested.

Dear Mel,

could you please specify which model you use? At what pressure do you degas, do you think around 100mbar (-900mbar) is sufficient?

I just bought a degasser that delivers 1L per minute. It is quiet and fast and removes more gas than the quick and dirty syringe method. I can find you the details if you are interested.

yes please do you have the reference?

JC,

We ordered this from BIOTECH ::

KIT.HF.500-S

High Flow Stand Alone Degasser inc. PSU and Clip Kit (500ml/min)

not cheap, but very efficient

Here is a link to what I use: silent compressor model BB24V. It comes in several sizes and this Youtube link allows you to hear how quite it is! This is sold in the UK.

https://www.youtube.com/watch?v=0iWYh5jnHY4

https://www.youtube.com/watch?v=9ECrq3lA-nc (WITH SOUND)

IT ALSO DRAWS A VACUUM.

CORRECTION!

My last post applies to a quite pressure pump ONLY. The vacuum pump we use is a Chinese brand Sciencetool model R300. It is also fairly quite, but maybe hard to buy outside of China. My experience is that high-vacuum pumps are noisy but you don't need a perfect vacuum unless you really want to boil water at room temperature or make ice...try it sometime. Wrap a flask in insulation material and draw a vacuum overnight. You should see ice in the AM.

I saw that someone suggested using ARGON gas to degas a solution. *Please, do not use Argon gas. Argon is soluble in water! That would ADD gas to the solution. You want to displace gas from the solution not add gas to it (please see the link below, "HPLC Solution Degassing, Sparging (Gas Choice Matters)", for a related article).

Note: Not applicable to your application, but the simplest way to degas a solution for HPLC use is to continuously sparge ultra-pure helium gas through it (use a 10 u SS frit and cross-linked Teflon tubing connected to a low pressure helium line). BTW: Regarding degassing for HPLC applications only...Yes, Oxygen does interfere with HPLC analysis using UV detector so displacing all of the O2 is a desirable result. Helium is not generally soluble in solution so does not contribute to negative effects (that is why we use helium!). It can be easily sparged through mobile phase solution using a porous solvent pickup frit so no no air is added or "next to" the solution/bottle (very easy and works great).

More info at this link (HPLC applications only): https://hplctips.blogspot.com/2013/05/hplc-solution-degassing-sparging-gas.html

the easiest way is to boil the water for a few minutes , and let it cool down.

Full agree with  Claude. We use an electric resistence to hot and boil water in lab, but we also use a small vacuum pump (not noisy) connected to a desiccator to slowly deaerated air and then to saturated very dense soil samples.   

I agree, boil / heat up water and maybe stir a little bit ('fish') that the gas bubbles get off the glass walls (and 'gasses out'). Not that these bubbles get back to solution if it cools again.

The problem becomes more interesting when you have a few thousand liters (6000 in our case) in an acoustic test tank. I don't claim what we have is perfect, but it seems to work:

1. Be patient, it can take months before you'll reach equilibrium.

2. We periodically run a calibration of a known transducer and hydrophone, noting when we achieve steady-state, this usually takes several weeks after the tank has been refilled.

3. Once you have a big tank full of (mostly) degassed water, keep it clean. You can use a vacuum siphon hose to remove precipitated solids from the bottom of the tank.

4. Decant water into 5 gal buckets prior to refilling the tank. These seem to settle out in a week or so.

5. Use only mild chlorine to disinfect your tank, 0.5 ppm is enough.

6. Make acoustic measurements in the morning while the tank is still relatively cooler, before the gases start to bubble out.

Here is an idea I've had but haven't tried:

- Use rainwater runoff to fill your tank. It's already at atmospheric pressure, and contains few dissolved solids (relative to groundwater) and has no added fluoride or chlorine.

in my opinion, you can pass pressurized ultra pure Helium gas through your liquid subjected to degas and keep the liquid under negative pressure (~2 PSI). What else you can do is keep the temperature of liquid low (

Degassing by exchanging helium for N and O will not help with hydraulic measurements becuse if your aim is to get maximum conductivity you want to dissolve gases while you measure Kh. If your aim is just to get a native Kh value then you do not need to degas at all! But you may want to filter your water to remove excessive particles. There are ultra-quiet vacuum pumps available from the UK. I use these all the time in my lab, the dB level from the pump is less then normal speaking dB level. Google ultra-quite pumps on a UK website.

I have always wondered why one would want to use completely degassed water. It makes no sense. You just need to remove large air nuclei (someone should calculate and measure which size class of air nuclei changes resistance). I think the main goal is to remove any large gas nuclei so that you are not introducing bubbles to bordered pit fields while perfusing, which may increase R. Since degassed water does not exist in the xylem system, using completely degassed water may even remove gas from the plant hydraulic system during perfusion since the water in the xylem should be in gas equilibrium with the surrounding tissue. Furthermore, I notice that many go through the pain of the degasding procedure, then pour the solution into a container which regasses it and then this solution sits for hours, sometimes longer, and thus allowing gas to diffuse back into the perfusion solution. With that being said, I use autoclved KCl solution, that I then put under vacuum using small amounts of solution at a time. Using a 60 cc hydraulic syringe i lock off the tip with a luer loc then pull back the plunger and agitate the system, repeat several times until the bubbling stops. Each time I push the air out, then relock it etc. Then i attach my syringe to the big hydraulic system and slowly push the fluid into the hydraulic head container that is closed in a plastic bag system (sort of like a baby bottle) to reduce contact with air. I am using a SSFM or pressure transducers to measure deltaP across a hydraulic resistor system. For me, I am really only concerned with having any bacteria and reducing the abundance of air nuclei as much as possible in my perfusion solution. Seems to work.

Boiling just works fine for leaf hydraulics. I was running some test comparing degassed water using a vacuum pump and a the boiling method. Does not matter that much. I'm getting the same results, but reduced my portable lab for 14 kg.

What about using an ultrasound bath? I usually use it for degassing HPLC eluents and works fine. Wouldn't it be suitable for hydraulics measurements as well?