liquid chromatography reagents

[drernesto]

Hello Dr. Randy,
Hope all is fine.
Do you recommend any good supplier of bulk liquid chromatography reagents water test in Eu or China?
Thanks!

 

[Randy Holmes-Farley]

I'm sorry. Liquid chromatography? As in HPLC (high performance liquid chromatography) or TLC (thin layer chromatography)?

I'm not familiar with any chromatography tests that typical reefers use.

Maybe this is a translation issue?

 

[drernesto]

To be franc I have no idea, a friend saw me testing my water and started to ask questions [emoji5]️
Let's say Hanna or Salifert... What's the concept of their reagents.
Thanks!

 

[Randy Holmes-Farley]

We know some of the ingredients of some kits, but not usually the concentrations used so that DIY replacement of the chemicals is not easy and not something I'd usually recommend unless someone has posted an entire DIY or standard method that you are following. :)

 

[drernesto]

Aha... Well I wish someone (as our idol reef chemistry Dr.) would make a DIY to follow! [emoji6]

 

[McMullen]

But………this doesn't sound like a better mouse trap. Test kits are pretty affordable.

 

[drernesto]

But………this doesn't sound like a better mouse trap. Test kits are pretty affordable.

Well It's not related to money... More than understanding they way they are working...
For example I was able to produce bacterias and it help me a lot by understanding how they are working...

 

[McMullen]

That's cool, you want to know the how and why. Things like that propel the hobby forward!

 

[JimWelsh]

Calcium test kits are typically EDTA titrations, using an indicator dye that complexes with Ca++ and changes color when there is an excess of EDTA. Typically, Mg is precipitated as the hydroxide to make it unavailable to the reaction. The dye is then added. A typical dye used might be Eriochrome Black T or, more likely, Hydroxynaphthol Blue. These dyes form a complex with the Ca++ ions that is red in color. The dye is blue in color when it has no Ca++ ions attached. As EDTA is added, the Ca++ ions want to complex more strongly with the EDTA than with the indicator dye, so the Ca++ ions are taken away from the indicator dye by the EDTA. At the endpoint, enough EDTA has been added to complex all of the Ca++ ions, leaving no red dye molecules left, so the indicator turns from redish/purple to pure blue.

I have developed my own DIY Ca test that is based loosely on the Hach Calcium Burette Titration method.

Is this the type of thing you are asking about?

 

[drernesto]

Calcium test kits are typically EDTA titrations, using an indicator dye that complexes with Ca++ and changes color when there is an excess of EDTA. Typically, Mg is precipitated as the hydroxide to make it unavailable to the reaction. The dye is then added. A typical dye used might be Eriochrome Black T or, more likely, Hydroxynaphthol Blue. These dyes form a complex with the Ca++ ions that is red in color. The dye is blue in color when it has no Ca++ ions attached. As EDTA is added, the Ca++ ions want to complex more strongly with the EDTA than with the indicator dye, so the Ca++ ions are taken away from the indicator dye by the EDTA. At the endpoint, enough EDTA has been added to complex all of the Ca++ ions, leaving no red dye molecules left, so the indicator turns from redish/purple to pure blue.

I have developed my own DIY Ca test that is based loosely on the Hach Calcium Burette Titration method.

Is this the type of thing you are asking about?

This is exactly what I'm looking for.
Thanks a lot!
Do you have any Infos on the rest of the tests, Kh, p04 no3...

 

[JimWelsh]

Do you have any Infos on the rest of the tests, Kh, p04 no3...

Well, Randy has already covered alkalinity very well in this article, and there is further discussion about it in this thread.

I've looked into PO4 and NO3 a little bit. PO4 is frequently done using the molybdate method. Google "phosphate molybdate seawater". NO3 is typically done by converting nitrate to nitrite, and then measuring the resulting nitrite. For some examples, try googling "nitrate reductase seawater". One interesting example (you may want to look at this website for more about the "IORodeo Colorimeter") can be found here.

For Magnesium, a similar technique as that I describe for Calcium is done, also using EDTA. Sometimes the Calcium is precipitated as the sulfate to make it unavailable to the reaction, and the Magnesium is then titrated just like I described for Calcium above. For my DIY Magnesium test, I first test for Calcium, and then I test for "Total Hardness" using an EDTA titration that measures both the Magnesium plus the Calcium. I then subtract the Calcium value from the Total Hardness value to derive the Magnesium. For my DIY Total Hardness test, I have found an indicator dye that gives me such an extraordinarily sharp endpoint that I can determine Total Hardness with an uncertainty of less than 0.5%, and more typically less than 0.3%, which means I can know my Mg to within +/- 5 PPM or so. I have also developed a "trick" to get similar precision out of my DIY Calcium test. Hach describes a combined Total Hardness and Calcium Hardness test, where both results are determined that you can read about here.

 

[drernesto]

Well, Randy has already covered alkalinity very well in this article, and there is further discussion about it in this thread.

I've looked into PO4 and NO3 a little bit. PO4 is frequently done using the molybdate method. Google "phosphate molybdate seawater". NO3 is typically done by converting nitrate to nitrite, and then measuring the resulting nitrite. For some examples, try googling "nitrate reductase seawater". One interesting example (you may want to look at this website for more about the "IORodeo Colorimeter") can be found here.

For Magnesium, a similar technique as that I describe for Calcium is done, also using EDTA. Sometimes the Calcium is precipitated as the sulfate to make it unavailable to the reaction, and the Magnesium is then titrated just like I described for Calcium above. For my DIY Magnesium test, I first test for Calcium, and then I test for "Total Hardness" using an EDTA titration that measures both the Magnesium plus the Calcium. I then subtract the Calcium value from the Total Hardness value to derive the Magnesium. For my DIY Total Hardness test, I have found an indicator dye that gives me such an extraordinarily sharp endpoint that I can determine Total Hardness with an uncertainty of less than 0.5%, and more typically less than 0.3%, which means I can know my Mg to within +/- 5 PPM or so. I have also developed a "trick" to get similar precision out of my DIY Calcium test. Hach describes a combined Total Hardness and Calcium Hardness test, where both results are determined that you can read about here.

Thanks a lot! These Infos are just what I needed! You're a savior [emoji4]

 

[JimWelsh]

You are welcome! Oh, and for the alkalinity titration, if you want to use an indicator dye instead of a pH meter, you can use a mixed indicator, such as the Bromcresol Green/Methyl Red indicator solution sold by Hach: http://www.hach.com/bromcresol-green-methyl-red-indicator-solution-100-ml-mdb/product?id=7640192430. Endpoint is somewhere between the blue-green start color and the pinkish-orange color you get when you overshoot. I describe the correct endpoint as a beautiful "Lavender" color -- just enough red to make it distinctly not blue or purple any more, but not enough to call it pink just yet.

 

[drernesto]

You are welcome! Oh, and for the alkalinity titration, if you want to use an indicator dye instead of a pH meter, you can use a mixed indicator, such as the Bromcresol Green/Methyl Red indicator solution sold by Hach: http://www.hach.com/bromcresol-green-methyl-red-indicator-solution-100-ml-mdb/product?id=7640192430. Endpoint is somewhere between the blue-green start color and the pinkish-orange color you get when you overshoot. I describe the correct endpoint as a beautiful "Lavender" color -- just enough red to make it distinctly not blue or purple any more, but not enough to call it pink just yet.

Thanks a lot!