Working on Automatic Tester, need help with preparing reagents

[Tariq-Shiwani]

Hi Randy,

hope you are doing good, this is my first thread ever.

My Background:
I am a software engeer with 25+ years of experience.
In hobby for past 4 years
along with the above electronics is my passion and I do a lot of DIY stuff.
no background of chemistry

Goal
I am working on an automated testing device which will work similar to Neptune Trident. (initially testing with nitrate)

Acheived
I've created a prototype device that passes a light through the cuvette filled with water sample reacted with reagent and on the other side there is a color sensor that senses the color and its intensity to determine the color shade.

To be done
prepare 5 samples with know concentration of nitrate and test using my device with my own reagent and then create a calibration curve for future use.

Need Help with
I tried peparing my own (Griess) reagent with following

• Sulfanilamide + Phosphoric Acid
• N-(1-Naphthyl)ethylenediamine dihydrochlorid

mixed these two solutions

this changes the color of the sample to slightly pink based on the nitrate concentration but the color intensity is too low to diferentiate between changes of the nitrate concentration targeted to be read i.e. between 0 and 75ppm


later figured that this this reagent is used to test NO2, upon further study I got to know that I will have to add copper to reduce NO3 to NO2, after adding copper the results were strange, the sample with nitrate present in it turned light pale pink and the sample with 0 NO3 turned a little pink.




any help in this regard would be highly appreciated, please pardon me if I've violated any rules as I am new to posting in forums.

 

[Randy Holmes-Farley]

This is a fine place for such a discussion, but I’ve never designed a nitrate kit.

They all do convert a portion (sometimes a very low fraction) of the nitrate to nitrite for detection chemically. Various metals are often used to perform that function, but I do not know exactly how much of what metals work best, and what physical forms (particle size, etc.).

 

[Tariq-Shiwani]

This is a fine place for such a discussion, but I’ve never designed a nitrate kit.

They all do convert a portion (sometimes a very low fraction) of the nitrate to nitrite for detection chemically. Various metals are often used to perform that function, but I do not know exactly how much of what metals work best, and what physical forms (particle size, etc.).

thank you for the quick response, the device I am working on is intended to perform all the common tests (alk, cal, mag, NO3, PO4, Zinc, Iron, Iodine, stronitum and silicat) and I will be working on preparing all those reagents myself, I know its a long project but I am sure it will keep me busy for the whole year or may be more.

would you be able to help me with these? I know you are really busy and will barely have time to respond me on my stupid questions, definitly I am not expecting your commitment towards this but your random hints would help me acheive my goal, however as I stated earlier I have 0 experience with chemistry so when I say hints I may need little more details

but I am happy that you responded to my post.

thank you so much

 

[taricha]

The hobby test kits that I am aware of use zinc powder to help with the reduction of NO3->NO2 for a nitrate test.
Is there a reason that you need to do the reagents from scratch for your tester? rather than use some hanna, red sea etc reagents?

 

[Tariq-Shiwani]

The hobby test kits that I am aware of use zinc powder to help with the reduction of NO3->NO2 for a nitrate test.
Is there a reason that you need to do the reagents from scratch for your tester? rather than use some hanna, red sea etc reagents?

There are going to be hundreds of tests, trial and errors, working with Hannah or any other reagents might get me bankrupt plus I don't live in US so they are not handy to grab and on top of it I am planning my device to perform 10 to 12 different type of tests I believe for some of them reagents are not really to common and easy to get

 

[luis angel]

very interesting, I wish you luck, following this one

 

[Dan_P]

There are going to be hundreds of tests, trial and errors, working with Hannah or any other reagents might get me bankrupt plus I don't live in US so they are not handy to grab and on top of it I am planning my device to perform 10 to 12 different type of tests I believe for some of them reagents are not really to common and easy to get

Water testing handbooks will either provide the recipe or a reference to the recipe for most water tests.

The last automated nitrate test I read about used a column of cadmium to reduce nitrate to nitrite.

 

[Tariq-Shiwani]

Water testing handbooks will either provide the recipe or a reference to the recipe for most water tests.

The last automated nitrate test I read about used a column of cadmium to reduce nitrate to nitrite.

Thanks, will try to find one that can lead me the right direction, please let me know if you know of any handbook that can cover all or some of it.

Will look into cadmium too, however I just had successful test of Alkalinity, I know there are recipes already provided on different forums and even one by our dear Randy but I wanted to do it without a pH probe so had to work with pH indicator and make it a single solution so I don't get to keep 2 different solutions for alkalinity test, so far had success with it but instead of titration I will be relying on color, will do a couple of more tests tomorrow with different known alkalinity samples, today's tests were performed on 3 different samples for which I did not know the exact alkalinity, I just knew all three had different alkalinity level.

 

[taricha]

please let me know if you know of any handbook that can cover all or some of it.

Methods of Seawater Analysis by Grassholf (third edition) is pretty thorough. It goes through multiple methods for each analyte.
If you need info that's cheap/free - it won't be nearly so comprehensive. You can search standard methods for water/wastewater and find the methods for individual tests.

 

[Tariq-Shiwani]

Methods of Seawater Analysis by Grassholf (third edition) is pretty thorough. It goes through multiple methods for each analyte.
If you need info that's cheap/free - it won't be nearly so comprehensive. You can search standard methods for water/wastewater and find the methods for individual tests.

Thank you

 

[strich]

Have you tried using ChatGPT to really get you started? Not suggesting it'll give you all the answers, but given that this information is not cutting edge or specialist bespoke chemisty, I bet it could do a pretty dang good job of answering down to a lot of deep technical detail. You would need to eventually back up any numbers/ratios it gives with real data, but it should get you a long way.

 

[Tariq-Shiwani]

Have you tried using ChatGPT to really get you started? Not suggesting it'll give you all the answers, but given that this information is not cutting edge or specialist bespoke chemisty, I bet it could do a pretty dang good job of answering down to a lot of deep technical detail. You would need to eventually back up any numbers/ratios it gives with real data, but it should get you a long way.

actually I started with ChatGPT I never went to a chemistry class so who else could have helped me with this, googling all this would take ages.

GhatGPT has been a good help but its inaccurate many times and provides wrong info but atleast it gives me hints to get started, so I am tankful to it.

for the device that I am working on, I didn't have to consult Dr. ChatGPT because I have a little experience with electronics and good experience of programming so google fills the gap here.

 

[Randy Holmes-Farley]

I’m happy to advise as I can, but I do not claim any specialized knowledge in how complex test methods are best devised and the books mentioned above would be where I’d start.

 

[Tariq-Shiwani]

I’m happy to advise as I can, but I do not claim any specialized knowledge in how complex test methods are best devised and the books mentioned above would be where I’d start.

thank you, I will keep posting my progress here, and will create another thread later where I will be posting progress of my device and maybe how to of the device along with all the information and resources needed to build one by anyone

 

[taricha]

No idea if it's helpful for your thinking @tariqms but here's how I'd rank some reef chemistry tests (including those from your list) from easiest to hardest to do in a reliable, repeatable, precise way.

Easiest
alkalinity
pH
Mg
Ca
Nitrite (NO2)
Ammonia
Phosphate
Iodine
Silicate
Potassium
Nitrate (NO3)
Hardest

Probably impossible because expected reef values will always be too low
Zinc
Iron

Probably impossible because the test methods are awful
Strontium

Not sure if you knew that nitrate is one of the hardest ones to nail down precision or not, but I wanted to share my opinion on that before you decide that's where you want to start.

 

[Tariq-Shiwani]

No idea if it's helpful for your thinking @tariqms but here's how I'd rank some reef chemistry tests (including those from your list) from easiest to hardest to do in a reliable, repeatable, precise way.

Easiest
alkalinity
pH
Mg
Ca
Nitrite (NO2)
Ammonia
Phosphate
Iodine
Silicate
Potassium
Nitrate (NO3)
Hardest

Probably impossible because expected reef values will always be too low
Zinc
Iron

Probably impossible because the test methods are awful
Strontium

Not sure if you knew that nitrate is one of the hardest ones to nail down precision or not, but I wanted to share my opinion on that before you decide that's where you want to start.

Thank you, I would prefer to do the hardest one first because if I am able to crack the hardest one then I am sure the others would be a piece of cake

But I appreciate that you care about it, if you guys keep motivating me like I will definitely crack them all

 

[Tariq-Shiwani]

While having break from Nitrate reagent, I worked on alkalinity reagent which doesn't require pH probe and here are the results for preliminary tests, I think it still require some fix because the color difference between two samples is not as much as the alk difference, it would be really difficult to map the tank sample's result to this calibration curve.

Maybe someone can chime in and help with some fix.

@taricha

 

[Tariq-Shiwani]

Hmmm, a little improvement??

 

[strich]

Curious why you're worried about total color change amount? Can't the photo sensor pick up any change?

 

[WillpoleReefers]

Hi

I am about to try using the method outlined in this paper for nitrate analysis: A simplified resorcinol method for direct spectrophotometric determination of nitrate in seawater, Jia-Zhong Zhang, Charles J. Fischer, Marine Chemistry,2006 . It is copyright but findable online. It differs from the commonly used methods in that it does not require a metallic reducing reagent and involves the simple addition of resourcinol and sulphuric acid. The downsides as published from autoanalyser perspective would seem to be the use of conc acid, maybe that use could be modified, plus that resourcinol solutions deteriorate with storage. On the face of it it looks attractive as a lab method in that it avoids cadmium column preparation, if it works. I also saw a nice way to make a cadmium column while researching nitrate, involves using Cd 1mm wire in about 1m of thin ptfe tubing, sounds easier than using filings …if the wire could be sourced or made, that’s the tricky bit.

A good read is the classic: A Handbook of Seawater Analysis, Strickland - scanned copy easily available online, lovely old book. I found an old copy in print, nice book to have.

Strikes me that nitrate may not be the easiest test to start with here .

Steve