Spectrophotometer question

[MarsRover]

Big fan of this stuff! Hack away friends

Following

 

[Mono]

Randy,

I picked up:

Loudwolf, TriSodium Phosphate (TSP) Na3PO4 99.9+% Ultra-Pure food grade
Shor, Sodium Nitrate, Reagent Grade (chemically pure) – 1 lb. bag

I actually have access to a photospectrometer at work which I can borrow so I can test this out with a pretty low overhead.

Anyway, I guess this is really good practice for "testing" my test kits and methods.

And now that I am thinking along these lines..

I am not sure if it's even possible for all of the parameters, but it seems like it would be a great reef chemistry project to put together a spreadsheet with recipes for preparing reference solutions for all of the basic parameters.

Ca
Alk
Mg
Ph
Nitrate
Salinity (OK, I'll work on this one.)


It seems like these would be useful to a lot of reefers.

 

[JimWelsh]

I do have a standard kitchen scale which measures in grams.

Even though Randy seems to think this is adequate, digital scales with 0.01g sensitivity can be purchased for under $20. Also, while I don't know what Randy has in mind for accurate volume measurement, I would consider something like a 1000 mL Class A volumetric flask to be a requirement for a project like this. If you're going to go to all the trouble to do this, you might as well spend just a little more money to get decent tools that will greatly improve the accuracy of the resulting standards (especially if serial dilutions are involved). Just my $0.02.

 

[Mono]

Jim,

I was thinking along the same lines. Definitely not cost prohibitive. As I mentioned I can borrow a spectrophotometer to see what I can do.

Thanks for the links. They look good.

Michael

 

[Mono]

The short answer is... this will work as long as the instrument is precise and accurate enough...The BRS video demonstrated this.

Actually I have been working on this problem for several months doing almost the exact procedure you outlined. I chose to use the HANNA Checkers and a HANNA Hand Held Spectrophotometer....They are much lower cost,although they are not programmable.

Here is my post that I made in October https://www.reef2reef.com/threads/diy-nitrate-test-meter.330892/#post-4114495

I have continued to work on this and have gotten some encouraging results. I have been focusing on the Nitrate and Iodine tests. I am satisfied with the HANNA Phosphorous Checker result I and getting so I did not include this test. I will be posting shortly my updated results on the Nitrate test. I have been focusing on the low range values for nitrate... 0-2 ppm because my initial work indicated that it was not reliable at these low levels (see October post) . My procedure is a bit different in that I run my calibration standards in saltwater then measure them and record the values on the different Checkers and Hand Held Spectrophotometers (HI-96702 Copper High Range). I then create a regression equation using Excel or a program called MyCurveFit and analize the equation for fit and estimate error. I pick the best one and used it as a predictor.

Because these are not programmable instruments I put the equation into Excel and enter the results of the meter reading and it gives me a projected value based on the regression equation...So I guess you could say Excel is the programmable feature of the instrument I have been using this on my nitrate test for several weeks and comparing it to other tests as a reference (NYOS, Red Sea Pro and some outside testing services) I have not explored all of the Hanna Checkers but have found the HI-736 Low Range Phosphorous Checker in conjunction with the Red Sea reagents and procedure works well for low range nitrate. The Iodine test is a bit more difficult because it is time temperature dependent. That being said, I think it is doable. My initial results indicate it can be repeatable and reproducible...The question remains how accurate is it, which I am still working on.

I will be posting the latest updates in the next few days...

Rick,

You are obviously way ahead. I am going to read your post over again later to make sure I get it all. And of course I will come back to it later when I start getting some results.

 

[Rick Mathew]

Rick,

You are obviously way ahead. I am going to read your post over again later to make sure I get it all. And of course I will come back to it later when I start getting some results.

Great...looking forward to the results...I should be posing my latest update soon that focuses on the low level nitrate testing

 

[Rick Mathew]

Randy,

I picked up:

Loudwolf, TriSodium Phosphate (TSP) Na3PO4 99.9+% Ultra-Pure food grade
Shor, Sodium Nitrate, Reagent Grade (chemically pure) – 1 lb. bag

I actually have access to a photospectrometer at work which I can borrow so I can test this out with a pretty low overhead.

Anyway, I guess this is really good practice for "testing" my test kits and methods.

And now that I am thinking along these lines..

I am not sure if it's even possible for all of the parameters, but it seems like it would be a great reef chemistry project to put together a spreadsheet with recipes for preparing reference solutions for all of the basic parameters.

Ca
Alk
Mg
Ph
Nitrate
Salinity (OK, I'll work on this one.)


It seems like these would be useful to a lot of reefers.

As Randy said as long as there is no titration involved only a reaction with color changes it should work...I find my Hanna Checkers work very well for Ca and Alk. My problem is with nitrate and Iodine...the color comparison charts are hard for me to distinguish between different levels and I have ti interpolate between levels...

 

[Rick Mathew]

Jim is correct about the equipment for setting up your standards...If they are not correct the error will generate false calibration curves and your test results will not be accurate...Getting these standards correct was the most challenging part for me...I will post a list of tools I used if that would help

Rick

 

[Rick Mathew]

Mono...Here is the list of equipment I got for making the calibration standards...the key ones were the two pipettes and the volumetric flasks...The graduate cylinders came in handy but were not necessary. You will for sure need the scale if you are going to weigh our powdered reagents....some of the amounts for the low concentrations are quite small even for 1000 mL volume. I used the Hach standard solutions as my starting point https://www.hach.com/ ....they were all liquids so the pipettes were critical. Some of the low level standards I had to make in two or more steps...first a 10 ppm then dilute that to required level... .25 ppm for example...I did all of my dilutions in sea water at the salinity level I keep my tank...35 ppt...Refer to the October post and Randy's comments to get the details...Also From Hach I believe....hope this helps...very excited to see your results

1) Four E's Scientific 100uL-1000uL High-Accurate Single-Channel Manual Adjustable Variable Volume Pipettes

https://www.amazon.com/gp/product/B0167YXMHK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

2) Four E's Scientific 1-10mL Single-channel Manual Adjustable Variable Volume Pipettes MicroPette

https://www.amazon.com/gp/product/B0167YXPKY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

3) Portable High Precision Milligram Digital Scale 20g x 0.001g for Weighing Gems,jewelry other Precious Objects + FREE Calibration Weight Kit - Class M2

https://www.amazon.com/gp/product/B00LL0YX0Q/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

4) 1000 mL Volumetric Flask

https://www.amazon.com/213W12-Karte...7059&sr=8-2&keywords=1000+mL+volumetric+flask

5) 100mL Class A Volumetric Flask with Acid Proof Polypropylene Stopper, Borosilicate 3.3 Glass - Eisco Labs

https://www.amazon.com/100mL-Volumetric-Polypropylene-Stopper-Borosilicate/dp/B0774YLT5R/ref=sr_1_2_sspa?s=industrial&rps=1&ie=UTF8&qid=1514577119&sr=1-2- spons&keywords=100ml+volumetric+flask&refinements=p_85%3A2470955011&psc=1

6) HUAOU 50ML Volumetric Flask with Solid Stopper

https://www.amazon.com/HUAOU-Volume...1-spons&keywords=50+ml+volumetric+flask&psc=1

7) Volumetric Flask, 10 mL, One Mark, Polyethylene Stopper, Class A, Lot Certified

https://www.amazon.com/Volumetric-F...577287&sr=1-2&keywords=10+ml+volumetric+flask

8) Measuring Cylinder Set - 4 Graduated Cylinders - 5ml, 10ml, 50ml, 100ml - Borosilicate Glass - Contains 2 Cleaning Brushes + 3 x 1ml Glass Pipettes

https://www.amazon.com/Measuring-Cy...577490&sr=1-7&keywords=graduated+cylinder+set

Rick

 

[Mono]

Rick,

Did you find inexpensive tips that fit the Four E micro-pipettes?

 

[Rick Mathew]

Rick,

Did you find inexpensive tips that fit the Four E micro-pipettes?

No I have not not for the 1-10 mL only the small one ....I only have one tip and it has to be cleaned and rinsed after each use. I just rinse it 3-4 times using RODI water...generally I don't even remove it from the body...just fill and purge...These tips are crazy expensive

This is the lowest cost I have found...at $1.40 each.... I will rinse and purge...I got 500 for the lower volume one for $9.0...Much more reasonable Amazon

https://www.amazon.com/Eowpower-Lab...rd_wg=jLie6&psc=1&refRID=B9AVYXEBV1ZY14K2AAZ0

https://www.amazon.com/Four-Es-Scie...rd_wg=RBSqf&psc=1&refRID=63HMJ33R85B8VDZJZZ19

 

[Mono]

Calling all you chemists,

Am I on the right track for making 1 liter of a 0.1% reference solution for NaNO3 and Na3PO4

 

[JimWelsh]

Not that I call myself a chemist, but the short answer is, "Yes." You should use the correct atomic masses from the periodic table rather than integers (this will only rarely matter much, but is still a best practice.). Work with full precision, but show fewer significant figures (e.g., three decimal places for the resulting weight if you are using a milligram scale); doing so will make the eyes glaze over much less!

 

[Rick Mathew]

Calling all you chemists,

Am I on the right track for making 1 liter of a 0.1% reference solution for NaNO3 and Na3PO4

I also do not call myself a chemist but it looks solid to me...Here is a good website to do the work for you...just enter the formula and up pop the answer...

https://www.lenntech.com/calculators/molecular/molecular-weight-calculator.htm

 

[Rick Mathew]

just a question... you are starting with .1%...That converts to 1000 ppm I believe. That is a fairly high concentration...you are going to need to do some serious dilution to get standards in the range for testing...I think this iss correct...some one check me on this

 

[Mono]

Yes, I will have to either start with a tenth or hundredth of a gram and then then dilute. I've ordered a more precise scale and will be getting the micro-pipettes. It's been a very long time since I've done anything like this and I just wanted to check that I'm headed in the right direction.

Jim and Rick thanks for the feedback.

 

[Mono]

Rick and Jim thanks for the feedback.

Yes, I am definitely aware that I will need to dilute the solution down to ppm or ppb.

I have ordered a new scale and plan on getting those micro-pipettes.

I just wanted to weigh in and see if my general approach was correct before I start worrying about the details.

 

[Randy Holmes-Farley]

Yes, I will have to either start with a tenth or hundredth of a gram and then then dilute. I've ordered a more precise scale and will be getting the micro-pipettes. It's been a very long time since I've done anything like this and I just wanted to check that I'm headed in the right direction.

Jim and Rick thanks for the feedback.

You can start at a higher level and dilute more times, but a lower range scale will introduce less dilution error.

 

[Rick Mathew]

Rick and Jim thanks for the feedback.

Yes, I am definitely aware that I will need to dilute the solution down to ppm or ppb.

I have ordered a new scale and plan on getting those micro-pipettes.

I just wanted to weigh in and see if my general approach was correct before I start worrying about the details.

Yes, I will have to either start with a tenth or hundredth of a gram and then then dilute. I've ordered a more precise scale and will be getting the micro-pipettes. It's been a very long time since I've done anything like this and I just wanted to check that I'm headed in the right direction.

Jim and Rick thanks for the feedback.

You are most welcome....I too am a bit rusty on my chemistry. Had two years of it in college but that was ages ago...but I have to say I have really enjoyed brushing up on some of it and especially enjoyed the lab work...keeps the mind fresh...let me know if there is any other way I can help

Rick

 

[Rick Mathew]

Yes, I will have to either start with a tenth or hundredth of a gram and then then dilute. I've ordered a more precise scale and will be getting the micro-pipettes. It's been a very long time since I've done anything like this and I just wanted to check that I'm headed in the right direction.

Jim and Rick thanks for the feedback.

Mono Here is the link to the post I mentioned about using the HI-736 Phosphorous checker to test for NO3 ---- https://www.reef2reef.com/threads/u...-hi-736-to-test-for-low-levels-of-no3.350062/