In an aqueous solution of methanol, there are sodium chloride, sodium carbonate, and sodium bicarbonate; how can the methanol content be analyzed?

Refer to GB/T 683-2006 \"Chemical Reagents – Methanol\" – the gas phase method. But what exactly is this sample of yours? This method may not be applicable in such cases...;P

Alternatively, distill the specific density and consult a reference table to determine the content (with temperature compensation); however, it won’t work if there are too many other volatile components in the sample.

I’ve considered the issue of evaporation, but I don’t know how to ensure that it evaporates completely； Another issue is the condensation and absorption of methanol; it’s not clear how to ensure that all of the methanol is condensed and absorbed. If any step fails, the process will not be successful.

For discussion only: Over thirty years ago, when working in a rice wine factory, the ethanol concentration in rice wine was determined in this way: 100 mL of rice wine sample was taken, 50 mL of water was added, and the mixture was collected in a 100 mL measuring cylinder using a coiled condenser; the concentration was then measured directly with an alcohol meter, along with the temperature. Since the alcohol concentration in yellow rice wine is low, the accuracy requirements for testing are not high, so this approach is feasible. If your sample has a high concentration, it may be difficult to prevent volatilization during distillation; it might be necessary to dilute it before distilling. The receiving container should have as good a seal as possible to minimize evaporation losses. Could we try using a standard sample to see the recovery rate, and thereby verify whether the method is feasible?

Thank you, I’ll give it a try. I used to be concerned about accuracy; I’ve tried using chemical methods to analyze the methanol content.

In an aqueous solution of methanol, there are sodium chloride, sodium carbonate, and sodium bicarbonate; how can the methanol content be analyzed? Are there any chemical analysis methods? There is likely no chemical analysis method for directly determining the methanol content; generally, a precision densitometer is used for testing, and filtration may be necessary. The error is only a few percent, unless there is too much salt present. If that doesn’t work, flash distillation can be used; by measuring the methanol content in the effluent, it’s possible to determine that the residual methanol in the bottom liquid is very low.

The amount of inorganic salts that methanol can dissolve has been analyzed; there is a complete set of data available. The only issue is that methanol itself cannot be analyzed directly. I’ve always wanted to find a way to analyze it in just one step, but my ideas are limited. I’m hoping someone might have a better method – after all, other people’s insights can be useful, and perhaps a casual remark from someone else could turn out to be the key to solving this problem.

Can’t we use direct gas-phase quantitative analysis?

If it is certain that the liquid contains organic substances primarily in the form of methanol, the chemical analysis method is quite simple: under sulfuric acid conditions, redox titration using standard potassium permanganate can be used to determine the methanol content with high accuracy. Or, total organic carbon can be analyzed using a TOC analyzer, and then converted to methanol.

Inorganic salts can clog the columns; it is an aqueous solution of methanol and inorganic salts, with a methanol content of around 90%.