Solid State Alk Sensor?!?!

[erk]

With all these alkalinity monitors and related equipment that are already on the scene, I was wondering if there was any work being done on an actual sensor that did not require titration. I know Seneye has something coming out, but that appears to calculate the carbonate level using CO2 concentration and pH. I did happen on the following links:

https://pubs.acs.org/doi/abs/10.1021/acssensors.7b00305
https://nsf.gov/awardsearch/showAward?AWD_ID=1155122&HistoricalAwards=false

They would indicate that a solid state total alkalinity sensor for use in saltwater will be available in the next few years. I can imagine they will be costly, but when some of the alkalinity monitors are retailing at around $500, a $500 sensor doesn't sound so bad if it lasts several yrs without me having to refill anything and can even take continuous measurements.

I'm definitely considering integrating one of these into my RPi controller if the price is right. How many of you will look at purchasing one of these if/when they become available?

 

[Randy Holmes-Farley Verified Community Expert]

The sensors you link also work by CO2 and pH.

 

[erk]

The sensors you link also work by CO2 and pH.

Good point. I should've read the whole summary first. I was mostly interested in the precision. I'm sure this isn't as accurate as a standard titration test(when done correctly), but having the ability to see when large shifts are happening would be invaluable.

I'm honestly interested in the Seneye alk sensor, but I haven't seen anything about it's precision, if I will need to replace components on a regular basis, and I'm guessing I'll have to purchase the base system to be able to use it. I would prefer to have a standalone sensor that I can integrate into my own controller.

 

[Randy Holmes-Farley Verified Community Expert]

Good point. I should've read the whole summary first. I was mostly interested in the precision. I'm sure this isn't as accurate as a standard titration test(when done correctly), but having the ability to see when large shifts are happening would be invaluable.

I'm honestly interested in the Seneye alk sensor, but I haven't seen anything about it's precision, if I will need to replace components on a regular basis, and I'm guessing I'll have to purchase the base system to be able to use it. I would prefer to have a standalone sensor that I can integrate into my own controller.

Mindstream is developing a similar product for reefers. At least they were. Not sure on its status.

 

[acrylic2k]

I have a solid state pH meter......... I know, not what you are looking for .....but they are cool.

No filling or soaking electrodes. Ion Selective Field Effect Transistor.

Stainless steel probes cant be broken easily.

 

[erk]

Mindstream is developing a similar product for reefers. At least they were. Not sure on its status.

I've been following them on Facebook. They post a status occasionally, but not sure how far they are from a complete product.

I have a solid state pH meter......... I know, not what you are looking for .....but they are cool.

No filling or soaking electrodes. Ion Selective Field Effect Transistor.

Stainless steel probes cant be broken easily.

The articles I posted mention using an ISFET to measure alkalinity. I'll look into these solid state pH probes. Would be interesting if I can implement a setup like the articles to compute alkalinity.

 

[erk]

@acrylic2k Where did you purchase your solid state meter? I found a source that lists a general purpose probe at $550.

 

[acrylic2k]

IQ Scientific made them. Then they were bought by HACH. then HACH discontinued them.
I am a lab "manager" and they are an easy improvement to implement. Fast response, accurate, and indestructible.
To be honest, you can kill them if you really try. Our lab just left a probe soaking overnight in 10 normal NaOH and that did it.

https://www.hach.com/h-series-h260g-laboratory-ph-ise-meter-no-probe/product?id=7640513849


A similar probe and meter combo is still made by Sentron in Denmark I believe.

 

[Randy Holmes-Farley Verified Community Expert]

I can’t see any sort of true alk meter since alk is not a single thing in the water. A bicarbonate meter maybe...

 

[Brendank]

I’ve been working on a carbonate alkalinity monitor/controller for a while. It’s an extremely difficult thing to measure using the CO2/pH relationship. For a reliable and robust carbonate alkalinity calculation, it requires a series of measurements of different parameters with very high precisions and accuracies that’s very difficult if not impossible with current commercially available sensors (at reasonable prices aka not >$10k). If my approach works that mitigates many of the challenge associated with sensor measurement issues, I might inquire to get a patent.

 

[JimWelsh]

I’ve been working on a carbonate alkalinity monitor/controller for a while. It’s an extremely difficult thing to measure using the CO2/pH relationship. For a reliable and robust carbonate alkalinity calculation, it requires a series of measurements of different parameters with very high precisions and accuracies that’s very difficult if not impossible with current commercially available sensors. If my approach works that mitigates many of the challenge associated with sensor measurement issues, I might inquire to get a patent.

I agree that the pH / CO2 calculation is quite challenging. That's why I am so skeptical of the Mindstream device.

 

[Brendank]

I’m not sure what the Mindstream research and development budget looks like and how many PhD’s and the field composition they have working it but if they don’t have it developed by now, it might be unlikely they’ll be able to get it developed. It might take someone with just the right combination of technical fields to get it prototyped.

 

[JimWelsh]

So, without going into too many specifics, what is the general nature of your unique approach to solving this problem that has evaded the rest of the scientific community thus far?

 

[Brendank]

Advanced numerical analysis

 

[Brendank]

.

 

[JimWelsh]

Advanced numerical analysis

I wish you all the best.

 

[Randy Holmes-Farley Verified Community Expert]

The Mindstream takes this approach of accurately measuring CO2 and alk. You might google it.

 

[Brendank]

It looks like the Mindstream device uses an indicator dye on the reagent disk to measure total pH instead of a pH probe and doing the conversion?

 

[Randy Holmes-Farley Verified Community Expert]

It looks like the Mindstream device uses an indicator dye on the reagent disk to measure total pH instead of a pH probe and doing the conversion?

Yes, that's what they say.