Working on Automatic Tester, need help with preparing reagents

[WillpoleReefers]

What do you want to preserve them from?

If they are dry, air oxidation is the main issue. Sealing them well is the best way. Hach uses metal foil for this purpose. Moisture also facilitates the oxidation. In a few situations, changing physical form might be an issue, if a more soluble crystal form slowly converted to a less soluble one. Moisture sometimes facilitates that conversion. Pharmaceuticals sometimes include oxygen or moisture absorbing devices in prescription bottles for these reasons..

Some liquid reagents might be low enough in concentration and have other characteristics that may allow microbial growth. How to deal with that would be very case by case.

In a very few instances, light (typically low wavelength UV or blue) can cause breakdown of chemicals. Dyes might slowly break down when absorbing their specific wavelengths since that can put them into an excited electronic state that may be more prone to degradation. .

I forgot to add the detail that I am storing my dry indicators in brown glass and away from light as was recommended.

Steve

 

[WillpoleReefers]

might be a little confusion here.
sulfanilic acid is used as a reagent in lab tests (and some hobby kits) to react with nitrite - that is looking for nitrate reduction - that is to see if the biological sample has reduced nitrate to nitrite.
https://www.austincc.edu/microbugz/nitrate_reduction.php

So if it turns red, then there is nitrite - NO2 present, and if no red color - then the nitrate - NO3 in the culture broth was NOT reduced to nitrite - and thus sulfanilic acid didn't do anything to the nitrate.

If it gives no color with the sulfanilic acid, then a bit of zinc powder is added and it goes red. Proving that there was a bunch of nitrate, and the microbes in the sample didn't turn any into nitrite - NO2.

One way others have gotten around the difficulty of dispensing solids is to do suspensions in liquids, and use magnetic stirrers to spin up the suspension before they dispense the liquid with their automated system.

Seems easier than trying to find/invent an all-liquid, sensitive, quantitative, saltwater nitrate test.

I understand it can be done in solution with trivalent vanadium as the reducing agent. But I think you don’t want toxic reagents ?

Steve

 

[Tariq-Shiwani]

I forgot to add the detail that I am storing my dry indicators in brown glass and away from light as was recommended.

Steve

Thanks, but because my ultimate goal is automated testing I need to go with all liquid and as minimum number of reagents as possible.

 

[Tariq-Shiwani]

I understand it can be done in solution with trivalent vanadium as the reducing agent. But I think you don’t want toxic reagents ?

Steve

I think vanadium would be too much for a hobby thing.

 

[taricha]

I am wondering how mastertronic or reefMaster SPA of kamoer is doing it.

mastertronic uses a magnetic stir bar. Most others probably would too.

Here's another hobbyist DIY creation. You'll find it interesting if you haven't checked it already.
https://www.reef2reef.com/threads/o...and-supplementation-anyone-interested.984363/

 

[Tariq-Shiwani]

mastertronic uses a magnetic stir bar. Most others probably would too.

Here's another hobbyist DIY creation. You'll find it interesting if you haven't checked it already.
https://www.reef2reef.com/threads/o...and-supplementation-anyone-interested.984363/

yes I came accross this thread, but the machine doesn't seem reliable to me, it looks very delicate and requires a good care, I am planning to build something similar to trident or mastertronic.

but yes attaching a stirrer with reagent bottle seems better solution to me, if I couldn't figoure out a way to make a liquid NO3 reducer then I would probably opt for it.

btw meanwhile I tried to prepare Phosphate reagent, I see a slight tint in the sample after adding reagents but the intensity doesn't change proportionally with the concentration of Phosphate in sample, I used sodium phosphate to increase the phosphate concentration in sample for testing purpose but didn't see any positive impact.

Reagent Preparation for Phosphate:
Solution A: added 250ml of concentrated H2SO4 into 750ml water.
Solution B: 10gm of Ascorbic acid into 50ml water and then add 50ml Solution A (requires to keep in dark bottle and temperature <8C, kept in dark bottle but in room temperature and it changed the color to brown, assuming it degraded so need to figure out a way to keep in room temperature)
Solution C: 12.5g of Ammonium molybdate in 125ml of water. 0.5gm of potassium antimony tartrate in 2ml water and then add both to 350ml of Solution A.

Test Method:
took 4ml of water sample added 2 drops(0.1ml) of solution A, let it sit for a mintue and then add 2drops of solution B, let it sit for a few minutes
(the sample was stirred after adding each solution)

Result:
the color changed slightly blue but is not proportioned to the concentration of phosphate.


reqire your valuable advice!!!

so far I have been successfull with only Alkalinity reagent, until I figure out a way for both NO3 and PO4 reagetns meanwhile I will start working on Ca / Mg which seems farily easy to me. lets hope I don't get any blocker while preparing them.

 

[Tariq-Shiwani]

I am using murexide for Ca titration , one thing to be aware of is that once made solutions deteriorate. The standard way to use the indicator is as a powder ground up with sodium chloride to dilute it. I use it as 1% in NaCl, adding a tiny scoop (size as per typical test kit scoops) before each titration. My recipe to measure Ca (plus Sr) is 6ml 1M NaOH plus 10ml seawater sample, all diluted to 50ml with RODI. I titrate with 0.01M disodium EDTA. 400 ppm Ca = 10ml EDTA. (ie vol EDTA x 40). Strontium error averages approx 4ppm with this method.

Mg is then done by combined Ca/Mg titration using Eric chrome black and a pH 10 ammonia/ammonium chloride buffer instead of NaOH and 0.03M Na2EDTA. Again the salt diluted indicator is stored dry.

No idea how long these indicators last in solution

Steve

have a look at this video
https://www.youtube.com/watch?v=U3-BKSyiCfQ&t=644s&ab_channel=WaterQualityAnalysisLaboratoryMethods

this guy is using liquid indicators, if you watch his video about preparing EBT solution in which he is using tri-ethanol amine or ethylene glycol monomethyl ether to prepare his liquid indicator solution.

so I am just wondering if we first prepare the liquid indicator and then mix it with buffer solution and store it as Solution A and then use EDTA as solution B for titration, would it work ? will it help improve shelf life of EBT solution? if this works then same should work for Murexide too because in his other video he is using the ethylene glycol to prepare his Ca Indicator.

btw how do you measure strontium with this method ? as far as I've understood, Total Hardness - Ca Hardness = Mg Hardness, where does strontium play its part here.

 

[Tariq-Shiwani]

somebody just sent these pictures to me, this may help guessing how things should work

 

[WillpoleReefers]

have a look at this video
https://www.youtube.com/watch?v=U3-BKSyiCfQ&t=644s&ab_channel=WaterQualityAnalysisLaboratoryMethods

this guy is using liquid indicators, if you watch his video about preparing EBT solution in which he is using tri-ethanol amine or ethylene glycol monomethyl ether to prepare his liquid indicator solution.

so I am just wondering if we first prepare the liquid indicator and then mix it with buffer solution and store it as Solution A and then use EDTA as solution B for titration, would it work ? will it help improve shelf life of EBT solution? if this works then same should work for Murexide too because in his other video he is using the ethylene glycol to prepare his Ca Indicator.

btw how do you measure strontium with this method ? as far as I've understood, Total Hardness - Ca Hardness = Mg Hardness, where does strontium play its part here.

Thanks, will watch. EDTA titration measures the sum of Ca + Sr. You can’t measure Sr separately by titration really. As has been pointed out here already by @Randy Holmes-Farley the Sr error is low in ppm as strontium is >2x Ca formula weight. A practical approach suggested in the literature for seawater analysis is just to correct the combined Ca/Sr figure by 4ppm to get Ca based on average NSW Sr, correcting an assumed 1% Sr error. I guess in a tank one could punch in a correction based on available ICP results for Sr. Personally I would love to play with an Sr selective crown ether and nail Sr analysis that way. But maybe that’s for another day

 

[Tariq-Shiwani]

I think vanadium would be too much for a hobby thing.

@WillpoleReefers

upon my initial checking it looked like vanadium is too much toxic, but after further research I came to a conclusion that it can be used in reagent, I am trying to arrange that and will test it, however I will be using Vanadium Pentoxide instead.

this will help me with phostphate test also as there is another recipe of phosphate reagent which contains ammonium metavanadate and vanadium pentaxoide can be used to prepare that.

 

[BZOFIQ]

@Borat does a lot of these kind of builds, I feel he'd be useful in this discussion.

Jak sie masz?

 

[WillpoleReefers]

@WillpoleReefers

upon my initial checking it looked like vanadium is too much toxic, but after further research I came to a conclusion that it can be used in reagent, I am trying to arrange that and will test it, however I will be using Vanadium Pentoxide instead.

this will help me with phostphate test also as there is another recipe of phosphate reagent which contains ammonium metavanadate and vanadium pentaxoide can be used to prepare that.

Definitely report how vanadium chemistry goes!