Dear Sir. Concerning your issue about the use HPLC for measuring the amount of Bisphenol A (BPA) or disodium salt of BPA dissolved in DMSO. A high performance liquid chromatograph y (HPLC) method was developed for the determination of bisphenol A (BPA) that had migrated into canned fruit and vegetables. For more details, I think the following below link and the attached file may help you in your analysis:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1637852/

Thanks

Dear Isam,

Thanks for your comment.

I had a look on the paper you recommended, however it is also mentioned; "detecting BPA in aqueous solution or BPA in acetonitrile or methanol", while my sample is dissolved in DMSO (Dimethyl Sulfoxide). I am wondering whether I can use HPLC to detect my BPA in DMSO or not?!

Regards

Nothing prevents you from injecting a sample of BPA in DMSO. DMSO is a relatively weak solvent so even if the sample matrix is 100% DMSO it will not significantly disturb the peak shape. However, the viscosity of DMSO is pretty high so it is preferable not to inject large volumes. If the sample concentration permits it, try injecting 5 microliters or less to avoid a high pressure pulse that can damage your column.

Thanks Chris,

Yes you are right, the viscosity of DMSO is quiet high, specially when I am using a 200 gr/lit concentration of BPA in DMSO.

Would you mind let me your opinion about:

1- Using 5 microliters of a sample of BPA in DMSO at about 200 gr/lit concentration?

2- As I need to add NaOH to obtain Disodium salt of BPA, how do you think about this ? I mean by the fact that it will be more viscose, do you think that HPLC still can be used? if yes, injection in how much volume you suggest?!

Thanks for your attention.

Aghil

At such a high concentration, I would dilute the solution in water and add enough NaOH to keep it in solution. At the concentrations you mention, I would dilute at least 100:1. It would be best not to add too much NaOH though because if the sample pH is too high, this may damage you column assuming you are using a silica based reversed phase column. I don't see any reason to add enough NaOH to form the disodium salt. If you add enough NaOH to convert it to the monosodium salt that should be enough to get it to dissolve in water.

Yes you are right, producing the monosodium salt in the solution can induce to keeping the samples in solution, however I need disodium salt of BPA for the next step of my process of producing Polysulfone in a poly-condensation reaction between Disodium salt of BPA and Dichlorodiphenyl Sulfone. It is the reason that I want to see whether the disodium salt of BPA as the intermediate product has been obtained or not.

regards

HPLC will not tell you whether or not you formed the disodium salt. It will tell you how much of the bisphenol A you have; from the pH and the amount of NaOH you can determine the charge state. You cannot run your sample through conventional columns at the pH you need for disodium salt formation; you would need a special column. Plus, as Chris points out, you will need to dilute your sample prior to analysis since your concentration is high (beyond the useful range of HPLC/UV), which will shift your equilibrium in any case. It is best to measure the BpA present, correctly, and then adjust the pH of your initial solution to drive the equilibrium to the disodium salt.

Thanks Mark,

Based on your comments as well as Chris's, I understand that:

1- HPLC can not be useful for my sample which is highly alkaline, Am I right?!

2- by dilution I will miss the production of Disodium salt and maybe it will change to monosodium salt! Is that correct?!

3- I could not get the last part of your comments, Could you please clarify it for me what do you mean exactly when you say "measure the BPA present and..."?! You mean measring the amount of BPA in the solution by HPLC or measuring the amount of BPA that I have used at the start of the test?!

Your attention would be highly appreciated.

Kind regards

The amount of BPA is the same whether it is present as the monosodium salt or the disodium salt. Take the pH of your analytical aliquot to neutral or slightly acidic and measure the amount of BPA present, then you can calculate it as the disodium salt, assuming your solution pH is sufficiently high to be in the disodium form. In solution the sodiums ions are ionic and thus will not affect the HPLC separation. Since you will have to dilute your sample into an analytically-useful range, as Chris points out, you can do this in a buffer that is compatible with HPLC columns and your detector.