Technical University in Zvolen
Question
Asked 13th Jun, 2014
How do you determine organic acids (acetic and formic) in a solution using a spectrophotometer?
How can we estimate the acetic and formic acid content in a solution using a UV-Vis spectrophotometer? If anyone has the protocol, kindly provide it as some protocols I have found on the internet are not working. Thanks.
Most recent answer
If you decided to determine acetic and formic acids via UV, you have to measure the absorbtion of the total of acids at 220nm, in the first step. Then submit an aliquot of the sample to oxidation of formic acid by HgO in a boiling water bath in a closed vial. Cool the oxidized sample and filter /or centrifuge/ the suspension. Measure UV spectrum of the oxidized sample. The absorption maximum of the oxidized sample should be proportionally reduced due to removal of HCOOH and would corespond to content of CH3COOH. From the difference between the both spectra /total - CH3COOH/ you can detrmine formic acid.
I would prefer to detrmine both acids by GLC on a Chromosorb 102 column, detection with TCD. Temperature 140 - 150 oC, H2 or He as a carrier gas.
Or I would use conductometric alkalimetric titration.
Note: if your sample represents H2O extract from some biologic sample, the UV spectra might not give you correct data due to acids interferrence /overlapping// with some other watersoluble extractives.....
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Popular answers (1)
Technical University in Zvolen
If you decided to determine acetic and formic acids via UV, you have to measure the absorbtion of the total of acids at 220nm, in the first step. Then submit an aliquot of the sample to oxidation of formic acid by HgO in a boiling water bath in a closed vial. Cool the oxidized sample and filter /or centrifuge/ the suspension. Measure UV spectrum of the oxidized sample. The absorption maximum of the oxidized sample should be proportionally reduced due to removal of HCOOH and would corespond to content of CH3COOH. From the difference between the both spectra /total - CH3COOH/ you can detrmine formic acid.
I would prefer to detrmine both acids by GLC on a Chromosorb 102 column, detection with TCD. Temperature 140 - 150 oC, H2 or He as a carrier gas.
Or I would use conductometric alkalimetric titration.
Note: if your sample represents H2O extract from some biologic sample, the UV spectra might not give you correct data due to acids interferrence /overlapping// with some other watersoluble extractives.....
5 Recommendations
All Answers (7)
University of Technology and Applied Sciences Salalah
Acetic/formic acid in solution can be determined by titrimetry and not by spectroscopy, I guess.
BASF
I cannot remember having a spectrometric provement for both acids separate, because this is not a practical apllication. A common analysis and quality parameter is a total acidity assay, you have test like the reflectoquant 116135
TOTAL ACIDITY TEST PH 7.0 METHOD: REFLECTOMETRIC WITH TEST STRIPS AND REAGENT 2.0 - 14.0 G/L REFLECTOQUANT®
for a quick use but I would suggest a titrymetric assay like potentimetric or conductometric tittration or a good Ion or Ion exchange Chromatography, I think the subject is less easier than it seems
1 Recommendation
In principle you could use absorption band near 220 nm to determine organic acids. For separate analysis you have to separate them by chromatography. Doing a web search you will find a huge number of references.
Technical University in Zvolen
If you decided to determine acetic and formic acids via UV, you have to measure the absorbtion of the total of acids at 220nm, in the first step. Then submit an aliquot of the sample to oxidation of formic acid by HgO in a boiling water bath in a closed vial. Cool the oxidized sample and filter /or centrifuge/ the suspension. Measure UV spectrum of the oxidized sample. The absorption maximum of the oxidized sample should be proportionally reduced due to removal of HCOOH and would corespond to content of CH3COOH. From the difference between the both spectra /total - CH3COOH/ you can detrmine formic acid.
I would prefer to detrmine both acids by GLC on a Chromosorb 102 column, detection with TCD. Temperature 140 - 150 oC, H2 or He as a carrier gas.
Or I would use conductometric alkalimetric titration.
Note: if your sample represents H2O extract from some biologic sample, the UV spectra might not give you correct data due to acids interferrence /overlapping// with some other watersoluble extractives.....
5 Recommendations
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