Lubricant detection in water

[Mt21]

Hey who has some ideas on how to measure polyalkene glycol (PAG) in the form of neptune aw - 32 hydralic lubricant ppm in swimming pool water?

It would be nice if its possible to do in a simplistic and repeatable way or if there is even some kind of process sensor that measures PAG.

Cheers

[studiot]

3 hours ago, Mt21 said:

Hey who has some ideas on how to measure polyalkene glycol (PAG) in the form of neptune aw - 32 hydralic lubricant ppm in swimming pool water?

It would be nice if its possible to do in a simplistic and repeatable way or if there is even some kind of process sensor that measures PAG.

Cheers

Pay a lab to do a proper sampling and perform IR spectrum analyses on the samples.

[CharlesBMoore01]

It would be nice if its possible to do in a simplistic and repeatable way or if there is even some kind of process sensor that measures PAG.

[DrP]

8 minutes ago, studiot said:

Pay a lab to do a proper sampling and perform IR spectrum analyses on the samples.

I think the water could make the IR quite messy. Would GC/MS work for this sample?

 

[studiot]

9 minutes ago, DrP said:

I think the water could make the IR quite messy. Would GC/MS work for this sample?

 

I said samples because there is no guarantee that distribution would be uniform in a large pool.

I assume that the contaminant arrive from machinery in the inlet or outlet so would suggest paying particular attention there.

 

I suggested IR because the equipment is cheap, widely available and long and well understood.

It also works in a non volatile situation, unlike gas chromatography.

 

I would also suggest that once initial calibration is done it would be easier for continued monitoring/quality control purposes.

 

However it is a long time since I have done any of this so perhaps the analytical chemists amongst us have better ideas.

[hypervalent_iodine]

16 hours ago, studiot said:

I said samples because there is no guarantee that distribution would be uniform in a large pool.

I assume that the contaminant arrive from machinery in the inlet or outlet so would suggest paying particular attention there.

 

I suggested IR because the equipment is cheap, widely available and long and well understood.

It also works in a non volatile situation, unlike gas chromatography.

 

I would also suggest that once initial calibration is done it would be easier for continued monitoring/quality control purposes.

 

However it is a long time since I have done any of this so perhaps the analytical chemists amongst us have better ideas.

 

IR would be a poor choice. As mentioned, the water (a strong IR absorber) would obfuscate the spectra and make quantification very difficult (or impossible), especially if you’re talking about ppm concentrations in swimming pools. I don’t think GCMS is a great choice for a polymer either, as it would be too big and unlikely to run through the column. The other issue is that PAG is not one single compound. You could potentially do it with LC with the right set up and correct detector, but I am not 100% sure on this. This seems to suggest it’s possible, but I didn’t read it thoroughly. 

[studiot]

6 hours ago, hypervalent_iodine said:

 

IR would be a poor choice. As mentioned, the water (a strong IR absorber) would obfuscate the spectra and make quantification very difficult (or impossible), especially if you’re talking about ppm concentrations in swimming pools. I don’t think GCMS is a great choice for a polymer either, as it would be too big and unlikely to run through the column. The other issue is that PAG is not one single compound. You could potentially do it with LC with the right set up and correct detector, but I am not 100% sure on this. This seems to suggest it’s possible, but I didn’t read it thoroughly. 

 

I agree that's conventional wisdom, but how about this gadget?

 

https://www.bruker.com/applications/environmental/special/analysis-of-aqueous-solutions.html

 

 

[hypervalent_iodine]

1 hour ago, studiot said:

 

I agree that's conventional wisdom, but how about this gadget?

 

https://www.bruker.com/applications/environmental/special/analysis-of-aqueous-solutions.html

 

 

 

It's interesting, but it still doesn't help the fact that IR would not be able to differentiate between the different types of PAG present, which would render any effort at quantification unreliable. Not to mention the undoubtedly huge cost of buying a dedicated machine from a company like Bruker. 

[studiot]

50 minutes ago, hypervalent_iodine said:

 

It's interesting, but it still doesn't help the fact that IR would not be able to differentiate between the different types of PAG present, which would render any effort at quantification unreliable. Not to mention the undoubtedly huge cost of buying a dedicated machine from a company like Bruker. 

 

I think we are guessing as to the circumstances around the OP desire to measure these parameters.

One off or a future continued programme?

An individual or a large organisation with multiple pools?

Location in relation to possible testing laboratories?

 

 

[hypervalent_iodine]

4 hours ago, studiot said:

 

I think we are guessing as to the circumstances around the OP desire to measure these parameters.

One off or a future continued programme?

An individual or a large organisation with multiple pools?

Location in relation to possible testing laboratories?

 

 

 

I don't think you are understanding what I am saying. PAG is not one compound of a specific chemical formulae; it encompasses many, many possible compounds. IR wouldn't to be able to distinguish between these and as such, you cannot correlate the absorbance of any particular peak to concentration in the same manner as defined by Beer-Lambert, meaning you would not be able to accurately or precisely quantify it. So again, IR is a poor choice and would not suit the OP's needs, regardless of how often they need the testing done. 

[studiot]

Does it matter which alkene or which glyc , poly, -ol it is in this instance?

Would you want your child swimming in any of them?

https://orgchemboulder.com/Spectroscopy/irtutor/alkenesir.shtml

 

Though I would really like a specialist to come up with a significantly better suggestion,

I would also like more background information.

Edited January 18, 2019 by studiot

[hypervalent_iodine]

48 minutes ago, studiot said:

Does it matter which alkene or which glyc , poly, -ol it is in this instance?

Would you want your child swimming in any of them?

https://orgchemboulder.com/Spectroscopy/irtutor/alkenesir.shtml

 

Though I would really like a specialist to come up with a significantly better suggestion,

I would also like more background information.

 

It matters if it is a single compound if they want to measure it at ppm levels, as stated in the OP.

Thank you for the tutorial in IR that you posted. As it happens, I use IR regularly, albeit for characterisation rather than quantification. In any case, I can’t for the life of me figure out why you have posted it here? It doesn’t refute anything that I have said wrt the suitability of IR for the OP’s stated intention. Moreover,  I would like to add that you are unlikely to see alkene stretches in this instance. These peaks are typically very weak, and would likely be obfuscated by OH peaks (if present), and the myriad of other peaks in there that would be there in greater number and thus have much higher absorbance.

I have to ask, why exactly are you being so stubborn on this point? You have been told by two people who work in chemistry that IR is not a good option in this instance, for the reasons stated. You stubborn insistence is confusing. I have in fact suggested another alternative, HPLC. You would need a particular type of detector to do it for these samples, but I cannot think of any other way to easily quantify aqueous solutions of PAG. 

@Mt21 you may also wish to ask your question at Chromatography Forum. It’s reasonably busy and has a lot of talented people there who specialise in quantification and the various pieces of equipment you might come across. I used to frequent there a lot when I worked in an analytical lab as a technician. 

[John Cuthber]

It's very water soluble, so extraction into a solvent won't work- pity, because that's ofte a very useful first step.

You could remove the water by simply boiling it off. The poly glycol will remain.

But, so will all the other stuff you find in swimming pools. Let's be polite and call it urea.

The urea would upset any attempt to identify the PAG by IR.

So IR is not going to get very far (and it's also not very sensitive)

The mixture of materials present is going to be complicated so it's probably best to try to unmix it before you do anything else.
The go-to method for sorting mixtures in the laboratory is chromatography.
As has been pointed out, this stuff is too involatile to try to GC it.

So we are looking at HPLC

There's no useful chromophore so UV detection's not going to work (not at ppm levels anyway).
So I think you are pretty much stuck with HPLC MS.

I hope you have plenty of money.

Edited January 18, 2019 by John Cuthber

[hypervalent_iodine]

7 minutes ago, John Cuthber said:

It's very water soluble, so extraction into a solvent won't work- pity, because that's ofte a very useful first step.

You could remove the water by simply boiling it off. The poly glycol will remain.

But, so will all the other stuff you find in swimming pools. Let's be polite and call it urea.

The urea would upset any attempt to identify the PAG by IR.

So IR is not going to get very far (and it's also not very sensitive)

The mixture of materials present is going to be complicated so it's probably best to try to unmix it before you do anything else.
The go-to method for sorting mixtures in the laboratory is chromatography.
As has been pointed out, this stuff is too involatile to try to GC it.

So we are looking at HPLC

There's no useful chromophore so UV detection's not going to work (not at ppm levels anyway).
So I think you are pretty much stuck with HPLC MS.

I hope you have plenty of money.

 

You can use use a Corona detector in tandem with HPLC, which would circumvent the need for a chromophore. Not sure if that would be cheaper than MS, but you’d need a decent amount of money either way I guess. 

[John Cuthber]

This sort of thing?
https://en.wikipedia.org/wiki/Charged_aerosol_detector

The last time I looked they weren't very sensitive- but that's probably improved and they will be cheaper than MS.

[hypervalent_iodine]

49 minutes ago, John Cuthber said:

This sort of thing?
https://en.wikipedia.org/wiki/Charged_aerosol_detector

The last time I looked they weren't very sensitive- but that's probably improved and they will be cheaper than MS.

 

Yes, those. I am not very familiar with them personally, but it seems like it would be workable for the OP. Thermo literature states that their current model can profile PEG quite well and quantify polyacrylic acid down to ppb levels in industrial cooling water samples.

[Mt21]

Some really helpful replies here. 

To give you some more context we have a commercial performance pool with multiple moving hydraulic lifts to create various stage configurations. Our hydraulic heat exchangers began leaking very slowly over a long period of time which manifested as increased micro-bubble formation when the water is agitated. Not helpful for visibility underwater.

So to prevent this from happening i would like to implement a daily or weekly test that would reveal increasing or decreasing trend of PAG in pool water samples.

We dont really need exact ppm, just need to look for a leak if the trend is upwards. Although it would be nice to know at what point visible micro-bubbles start so we know how much to dilute with fresh water.

Edited January 20, 2019 by Mt21

[John Cuthber]

Aha!
That's a different problem.

Can you add something like fluorescein to the hydraulic fluid?
If so, then you can look for leaks using a black light lamp.
https://en.wikipedia.org/wiki/Dye_tracing

Trickier underwater but it tells you where the leaks are and, also, you can follow the fluorescein concentration in the water over time much more easily. 

(A fluorescence detector for an HPLC system is much cheaper than a mass spectrometer).

Other tracers could also be used- it depends what you can measure easily.

[Mt21]

18 hours ago, John Cuthber said:

Aha!
That's a different problem.

Can you add something like fluorescein to the hydraulic fluid?
If so, then you can look for leaks using a black light lamp.
https://en.wikipedia.org/wiki/Dye_tracing

Trickier underwater but it tells you where the leaks are and, also, you can follow the fluorescein concentration in the water over time much more easily. 

(A fluorescence detector for an HPLC system is much cheaper than a mass spectrometer).

Other tracers could also be used- it depends what you can measure easily.

We had discussed using dye, however the concern with that would be if its a small leak somewhere hard to see we may fill the pool with dye that lights everything up during shows...

[John Cuthber]

Chlorine kills fluorescein- it may take a while.

[Mt21]

15 hours ago, John Cuthber said:

Chlorine kills fluorescein- it may take a while.

Hmm that is interesting. Should be no problem in the pool then, and an increased chlorine demand would also be a indicator....

[John Cuthber]

An increased demand for Cl2 might indicate a leak anyway.

The chlorine will probably react with the hydraulic oil.