Method for quantifying permanganate-reducing compounds
View Patent ↗A method for quantifying the permanganate-reducing compounds (PRCs) in an acetic acid sample is disclosed. The method comprises establishing a correlation between permanganate absorbances of standard samples and their PRC contents and determining the PRC content of the acetic acid sample by measuring its permanganate absorbance of a reaction mixture containing a standard permanganate solution and the acetic acid sample. The permanganate absorbance is obtained by subtracting the manganese dioxide absorbance from the absorbance of the mixture.
1. A method for quantifying a permanganate-reducing compound (PRC) content of an acetic acid sample, comprising:
(a) measuring a permanganate absorbance of a reaction mixture comprising a known amount of a standard permanganate solution and the acetic acid sample at a selected wavelength from 460 nm to 580 nm at a set reaction time wherein the permanganate absorbance is determined by determining manganese dioxide absorbance and subtracting the determined manganese dioxide absorbance from the absorbance of the mixture;
(b) adding a known concentration of PRC to the acetic acid sample to produce a spiked sample;
(c) repeating step (a) with the spiked sample to measure the absorbance of the reaction mixture of the spiked sample (A sp );
(d) measuring the permanganate absorbance of a blank sample (A BL ) and
(e) determining the PRC content of the acetic acid sample by:
[PRC] AA =( A BL −A AA )×[PRC] sp /( A AA −A sp ),
wherein
[PRC] AA is the PRC content of the acetic acid sample,
[PRC] sp is the spiked PRC concentration,
A sp is the absorbance of the reaction mixture of the spiked sample and the standard permanganate solution,
A AA is the permanganate absorbance of the reaction mixture of the acetic acid sample and the standard permanganate solution, and
A BL is the permanganate absorbance of the mixture of the blank sample and the standard permanganate solution.
2. The method of claim 1 wherein the manganese dioxide absorbance is determined by a baseline drawn across the base of a permanganate absorption band.
3. The method of claim 1 wherein the standard permanganate solution is a potassium permanganate solution.
4. The method of claim 1 wherein the set reaction time is from 10 to 30 min.
5. The method of claim 1 wherein the blank sample is selected from the group consisting of water, alcohols, carboxylic acids, amides, nitriles, and mixtures thereof.
6. The method of claim 5 wherein the blank sample is water.
7. The method of claim 1 wherein a solvent is used to form the mixture.
8. The method of claim 7 wherein the solvent is selected from the group consisting of water, alcohols, carboxylic acids, amides, nitriles, and mixtures thereof.
9. The method of claim 8 wherein the solvent is water.