Chromatography Forum

Dear all,

I was trying for the past several months to separate nitrate and nitrite from the water sample. I am using the CBM 20A HPLC system enabled with the c-18 column. Kindly, advise me with the best possible methods.

Thank you for your time and effort.

Hi skiran, are you serious about that question? You need an anion exchange column for anions - no chance with a C18.

You need an anion exchange column for anions - no chance with a C18.

Ion-pair chromatography...

You can try something with RP, but I am not sure how well it will work. Most of the RP columns have some residual silanols. You need to inonize these silanols by going to higher pH, something like 6-8. You will be exploring ion-exclusion mechanism. Your flow rate needs to be 25% of you usual rate, but you are expanding this region 4 times because of the lower flow rate (6.5 min for 150 mm column, 10 min for 250 mm column). Nitrate/nitrite will elute BEFORE void, but might be separated. I don’t know how much organic will give you better results, try to explore 20-70%. Use 10-20 mM buffer.

Alternatively you can use one of our methods:
https://helixchrom.com/compounds/nitrate-ion/

Contact me through our website “Contact Us” if you have any question or would like to discuss other options.

You can also try to use a bare silica column with the same approach, but if you start going up in ACN (to 70-90%) you will start seeing effect of HILIC (watch for solubility of salt buffer in high ACN mobile phase) and your compounds might start retaining and separating by combination of HILIC and anion-exclusion mechanisms. Not sure about peak shape, probably is not going to be great.

Dear all,

I was trying for the past several months to separate nitrate and nitrite from the water sample. I am using the CBM 20A HPLC system enabled with the c-18 column. Kindly, advise me with the best possible methods.

Thank you for your time and effort.

How are you going to detect mentioned anions ?

Hi skiran, are you serious about that question? You need an anion exchange column for anions - no chance with a C18.

I have followed this article reported the Simultaneous determination of...
(https://www.ajol.info/index.php/sajc/ar ... le%20phase) Pl. let me know, the same can be followed for the qualitative measurement of nitrate and nitrite ...
thanks

Dear all,

I was trying for the past several months to separate nitrate and nitrite from the water sample. I am using the CBM 20A HPLC system enabled with the c-18 column. Kindly, advise me with the best possible methods.

Thank you for your time and effort.

How are you going to detect mentioned anions?

We are using SPD-20A UV-Vis detector attached to CBM 20A

Hi skiran, are you serious about that question? You need an anion exchange column for anions - no chance with a C18.

I have followed this article reported the Simultaneous determination of...
(https://www.ajol.info/index.php/sajc/ar ... le%20phase) Pl. let me know, the same can be followed for the qualitative measurement of nitrate and nitrite ...
thanks

Dear Skiran,
in this article they did not use a C18 column - Synergi Polar is reversed phase material, not C18, but an ether-linked phenyl phase with polar endcapping. Apparently the polar endcapping has some anion-exchange capability. If you look at the chromatograms in the mentioned article, you will find that this is at best a quick-and-dirty method. NO3 has a k<1.
If you really want to use a C18 column, you will need an ion-pairing reagent. But I would suggest to think about buying a diffent column.