[scientizscht (OP)]

no glucose reacted

How do you know?

But, the most likely answer is that diffusion from the air into your reaction vessel was too slow.
Did you put the solution in a shallow flat tray, a beaker or a conical flask?

I measured glucose with HPLC. Could it be a possibility that glucose and gluconate where measured together? I have not been able to find online whether HPLC can distinguish between glucose and gluconate.

The reaction took place in a square beaker and the solution had a square shape.

[Bored chemist]

I have not been able to find online whether HPLC can distinguish between glucose and gluconate.

Well, it would if I was doing it but it seems that you don't know how, because, if you did, you would have checked that first.

[scientizscht (OP)]

I have not been able to find online whether HPLC can distinguish between glucose and gluconate.

Well, it would if I was doing it but it seems that you don't know how, because, if you did, you would have checked that first.

How would you do it? Do you use special columns or methods?

[Bored chemist]

The first thing I would do would be google it and see if someone has done it before.
Something like this
https://www.shodexhplc.com/applications/lc-ms-analysis-of-glucose-and-gluconic-acid-vg-50-2d/

The other thing I would do would get a sample of the gluconic acid.
That way I could measure it as well as measuring glucose.
If, for example, 1% of your glucose is oxidised, it will be difficult to measure the change in concentration- especially as there will be some evaporation  when the material is exposed to the air.
But if 1% of the glucose if converted to the acid, you will see the acid easily.

[scientizscht (OP)]

The first thing I would do would be google it and see if someone has done it before.
Something like this
https://www.shodexhplc.com/applications/lc-ms-analysis-of-glucose-and-gluconic-acid-vg-50-2d/

The other thing I would do would get a sample of the gluconic acid.
That way I could measure it as well as measuring glucose.
If, for example, 1% of your glucose is oxidised, it will be difficult to measure the change in concentration- especially as there will be some evaporation  when the material is exposed to the air.
But if 1% of the glucose if converted to the acid, you will see the acid easily.

How exactly, will I 'see' (I assume measure) the acid? Don't forget the solution already has strong buffer salts, e.g. sodium phosphate.

[chiralSPO]

Well... how do you measure ("see") your glucose on the hplc? If you're using a mass spec detector, please stop injecting phosphate buffer into it.

[scientizscht (OP)]

Well... how do you measure ("see") your glucose on the hplc? If you're using a mass spec detector, please stop injecting phosphate buffer into it.

I was told that phosphate buffer does not interfere with HPLC/RID glucose detection.

[Bored chemist]

Are you using a mass spec detector?

[scientizscht (OP)]

Are you using a mass spec detector?

Nope, a Refractive Index detector is used.
Is it better to use Mass spec? I will have to ask a lab to do it.

[Bored chemist]

Is it better to use Mass spec?

Probably not in this case.

Do you have or can you get  gluconic acid?

[chiralSPO]

Glad you're using refractive index detector (I wanted to check that you weren't trashing a mass spec with phosphate before I knew what exactly you were doing--not to leap to conclusions baselessly, but to make sure you weren't making a costly error--glad that is not the case!)

As Bored chemist says, if you have some gluconic acid, you can inject a sample that has the same buffer, mobile and stationary phases, and see if it has a similar retention time. You can also spike your glucose solution with it (maybe at a few concentrations) to see if its in there too.

[scientizscht (OP)]

Is it better to use Mass spec?

Probably not in this case.

Do you have or can you get  gluconic acid?

I don't think so. I think I will need to invest in the special gluconate columns, I suppose, thanks!

[Bored chemist]

I don't think so.

Why not?
Gluconic acid (or sodium gluconate) is a lot cheaper than a new column.