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!

 

[Tariq-Shiwani]

so here is an update:

vanadium didn't work (I was able to get vanadium pentoxide, couldn't find vanadium chloride)

what worked:
solution A of original recipe is sulfanilamide which has to be prepared in HCl, the only modification I made is before mixing sulfanilamide into HCl I added zinc dust to it.


10gm of Zinc Dust in 50ml of HCl (this takes time to disolve so after mixing it let it sit for 24 hours)

then use this solution to prepare the sulfanilamide solution A.

the one on the left is the sample from my tank and the one on the right is again sample from my tank but added 10 drops (0.5ml) of Sodium Nitrate standard solution. (to make up the same volume for left side sample, I added 10 drops of my tank water to it)

Process:
3ml of water sample (before adding drops so total volumne is 3.5ml)
4 drops of Solution A (mix well, let it sit for 60 seconds)
2 drops of Solution B (mix well, let it sit for 2 minutes)

To be done (for manual testing):
prepare known samples
test individually
take pictures of each result
use any image tool to read the RGB value of the colors from pictures
prepare a shade card and print.

for my automatic testing, I will prepare the calibration curve use the known samples.

hope this helps anyone here looking for the DIY reagent.

I am not claiming the credit of griess reagent, but this modification is my own, hope this modified reagent will be known by my name


Phosphate reagent is still under research, meanwhile I will start working on Ca and Mg.

thank you everyone for your support, on my next visit to states I will bring some of it along and ship it to you guys (whoever is interested).

and if you make one by yourself please do let me know your feedback and experience.

 

[taricha]

the one on the left is the sample from my tank and the one on the right is again sample from my tank but added 10 drops (0.5ml) of Sodium Nitrate standard solution

So what is the sodium nitrate standard solution?
Wondering if that pink is like 1ppm nitrate (yay) or more like 50ppm (yikes)?

 

[Tariq-Shiwani]

So what is the sodium nitrate standard solution?
Wondering if that pink is like 1ppm nitrate (yay) or more like 50ppm (yikes)?

Good question, I missed that part.

I had prepared 1% of stock solution of sodium nitrate and diluted it further by taking 10ml and mixed 1L of water. Will test this sample with Hanna and update.

You are right if it's 50ppm then we will have a hard time reading the absorbance between 0ppm and 100ppm. And will be impossible to tell the difference visually.

Because I was struggling to get it working with liquid reagent, my focus was to achieve that first. So I just used a few drops of it to see if the color is developed or not. But you are right, Well now we need to dive further to test the sensitivity of our reagent.

Thanks for highlighting it.

 

[taricha]

I had prepared 1% of stock solution of sodium nitrate and diluted it further by taking 10ml and mixed 1L of water.

Gotcha!
so very roughly. 1% NaNO3 = 10,000ppm NaNO3 *( 62.0/84.99) = 7,300 ppm NO3.
7300ppm NO3 *(10/1000) = 73 ppm NO3 in your diluted stock solution.

the one on the right is again sample from my tank but added 10 drops (0.5ml) of Sodium Nitrate standard solution.

3ml of water sample (before adding drops so total volume is 3.5ml)

so 0.5mL of 73ppm in 3.5mL total gives 73 * (0.5/3.5) = 10.4ppm NO3.

so based on that stock description - the difference in those two pinks is 10ppm NO3.

maybe good enough. depends on the digital eyeball.

 

[Tariq-Shiwani]

So what is the sodium nitrate standard solution?
Wondering if that pink is like 1ppm nitrate (yay) or more like 50ppm (yikes)?

@taricha you were right, here is the result. but I think its still readable by digital eyeball

for manual testing, we can use same method as salifert, i.e. compare the color against the color card by looking from the top to bottom, which shows better color shades.

however I did some reasearch and figured that the mixture I prepared by adding zinc dust into HCl became zinc chloride and when this is mixed with water zinc disassociate from chlorine, so when added this solution to sample chlorine interfere with the reduction process of NO3.

so now I have prepared a zinc sulfate solution by adding zinc dust to sulfuric acid and left it to dissolve completely, will test it tonight.

thank you for highlighting the this, but I guess we are still good to go.

 

[Tariq-Shiwani]

Gotcha!
so very roughly. 1% NaNO3 = 10,000ppm NaNO3 *( 62.0/84.99) = 7,300 ppm NO3.
7300ppm NO3 *(10/1000) = 73 ppm NO3 in your diluted stock solution.



so 0.5mL of 73ppm in 3.5mL total gives 73 * (0.5/3.5) = 10.4ppm NO3.

so based on that stock description - the difference in those two pinks is 10ppm NO3.

maybe good enough. depends on the digital eyeball.

my bad, it was potassium nitrate not sodium nitrate, the molar mass of KNO3 is higher but the concentration was higher than the calculations you performed, actually I prepared this solution around 3 weeks ago and had prepared multiple samples to test with hanna unfortunately the concentration was so high that I wasted almost 5 to 6 reagent pillows and wasn't able to measure the NO3. it was higher than hanna range, so I don't recall which sample I kept. sorry for not being clear on this.