Hello Pavan

For the quantification of your potassium formate and the ionic impurities I would recommend Ion Chromatography (IC). You might also consider ICP-MS or AAS/AES for the determination of metal cations. The methods you mentioned are the methods of choice for organic impurities. A quick XRF analysis would tell you if you have some other metals salts present in your sample before running more time consuming experiments.

Hello Willi,

I was looking into Ion Chromatography as well. However, I had a query. Upon exposure to the environment, the solution of potassium formate turns brown. I wanted to quantify if this solution contained any dissolved impurities such as Sulfur dioxide or nitrogen oxides. Do you think Ion Chromatography can solve this problem?

In addition, we also have an Inductively Coupled Plasma Mass Spectrometer. Do you think instrument is feasible for the said analysis?

SO2 and NO2 can also be measured by IC. In these cases you need to oxidize an aliquot of your solution to sulfate and nitrate to be detectable. Not sure how you could proceed for other nitrogen oxides.

If we use ICP-MS, we do not need to oxidise any compounds, right? We basically want to test the grade and impurities that present as it is in the solution. Therefore, I was asking.

By taking advantage of its characteristic of being soluble in water at 18 degrees Celsius and insoluble in diethyl ether, purer potassium formate can be obtained by extraction.

Dear Pavan,

ICP-MS is for sure a good starting point. But all in all the answer to your question depends on the type of impurities you are looking for.

For inorganic impurities (other metals than potassium) this is one method of choice.

To clarify on other organic impurities (besides formic acid) ICP-MS will not work and other methods including LC-MS and NMR are needed...By the way: based on which type of analytics did you conclude that your material is impure?

Good luck

Alfred

The entry for potassium formate in the Merck Index is of interest (I've expanded abbreviations):

"Colorless, deliquescent granules. Density 1.91 g/cm3. Melting Point 167 °C, decomposes at higher temperatures with evolution of hydrogen. Soluble in 0.4 parts of water. The aqueous solution is practically neutral. Keep tightly closed."

It sounds like you need to store it in the presence of phosphorus pentoxide to stop it picking up water!

X-ray powder diffraction could well be useful but keeping the sample dry would be challenging.

Check the Melting Point (if you haven't already).

What's the origin of your sample?

David

It's depends upon what impurities present in sample.

if Alkali metals present it's to be analyzed by Flame photometer

any organic material present it can be extracted in solvent then measured by GC.

David Beveridge We actually sourced it from a local vendor and therefore do not know the nature of the solution.

Hello, everyone; thanks for the responses. So, to give you a better picture, we basically have a pure formate salt from labs that produces a colourless and transparent solution upon dissolving in water.

The one from the local vendor produces a yellowish shade, and when this salt solution is continuously exposed to the atmosphere, the solution almost turns black.

Upon using filters for purification, the solution colour became lighter, but it is still a deep shade of yellow, which is darker than the original solution. My guess is that the sulfur oxides might have reacted with the potassium formate solution.

The local vendor said that the impurities include KCl, but I want to know if any atmospheric constituents dissolve in the potassium formate solution due to exposure.

Any insights would be highly appreciated. Additionally, are there any methods which can help me quantify both organic and inorganic impurities.

Thank you.

Alfred Ross

Dear Alfred,

The grade salt produces a transparent solution, while the local vendor salt produces a yellowish solution and even after purification using filters it retains some of its colour and this is why I concluded that the impurities must be dissolved ones. I actually have no idea about the nature of the impurities.

You performed GC-MS test, in this test all impurities are Identify.

.

Dear Pavan,

this can be tricky, because even very small amounts of coloured compounds may cause this impression...all methods discussed above may succeed or fail. Try anything which is available (always in comparison with the clear reference)....

Good Luck

Alfred

Dear Alfred,

Thanks, I will try out different methods surely and update if I get any conclusive results.