Analysis method for methanol content in 10-50% methanol aqueous solutions?
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The product uses methanol as the recrystallization solvent; during the recrystallization process, methanol gas and water vapor are released, and upon condensation, a methanol-water solution is obtained with a concentration of approximately 10–50%. What is the analytical method used to determine the concentration of methanol in this solution? Please give me some advice, thank you!
It can be analyzed by gas chromatography. It seems there are methods for analyzing methanol on the forum; you might want to take a look. http://bbs.hcbbs.com/viewthread.php?tid=399663 Analysis of finished methanol
Reply to 2# yuanyao9394: Can gas chromatography only analyze trace amounts of water? Or can it only analyze the purity of methanol and not its concentration? Can it be analyzed when the water content is so high? It is estimated that only chemical analysis methods can be used to determine relatively high methanol concentrations in aqueous solutions, right?
By measuring density, the concentration can be determined quickly and accurately.
1. As mentioned above, it is possible to compare the contents based on density to obtain results. 2. Titration can be used for determination. 3. For gas chromatography, various types of columns can be utilized; if the goal is simply to measure the contents of methanol and water, a 5m PT column along with a TCD detector will suffice (concentrations from 0 to 100 are no problem)
Gas chromatography can be used for this; I have previously sent samples for the determination of the NMP and EA contents in aqueous solutions, and the results were between 5% and 20%. The choice of analysis method and column is important. I contacted a testing institution directly at the China Institute of Testing Technology for this purpose
1. The simplest method is to measure density, but be mindful of the effects caused by temperature changes； 2. To determine the water content, Kjeldahl titration or Kjeldahl electrometric method is used, as these are the most accurate approaches ； 3. Redox titration to determine the methanol proportion, with the same accuracy as the previous method ； 4. Viscosity method: Water has a much lower viscosity than methanol, and by using a viscometer, it is possible to estimate the proportion of methanol ； 5. Colorimetry: An anhydrous transition metal salt is added, and the speed and extent of color development are observed to roughly determine the proportion of methanol ； 6. Dielectric constant measurement, capacitance method; such instruments are relatively rare. Chromatography is the least favorable option, as the proportion of water is too high, which has a significant impact on ordinary columns.
Reply to 5# dalian*aochao: What kind of PT column are you referring to? Is it polyethylene glycol 400?
Reply to 8# chenhaidong5758: Porapak-T’s columns
Reply to 7# qugd: I would like to ask the experienced colleagues how to determine the methanol content in methanol-water solutions using redox methods. Are there any relevant standards for this? We have also been testing the methanol content in wastewater recently (accuracy isn’t required to be very high), but we haven’t found a good method for detection; we would appreciate any advice you can offer!
Reply to 1# chinazwr: Sir, if you have found any viable and simple testing methods, I hope you can share them! Thank you!