Science Buddies: "Ask an Expert"

Hi,

I need to find a procedure to quantitatively measure the oxidation for vegetable oil used in deep frying? Do we need to measure the amount of Peroxide in it or their is another way that can be done in school? Please i need it as soon as possible it is urgently needed by tomorrow.

Thanks a lot

Hi and welcome to Scibuddies,

The only reaction I know of that allows you to measure lipid oxidation quantitatively is an assay for the oxidation product malondialdehyde. Are you already familiar with this?

I have done it two ways. One is using thiobarbituric acid to produce a fluorescent compound and the other is by using Schiff’s reagent to make a colored product. Let me know if this would help you and I will repost with the method. The colorimetric reaction could be done at school if you can borrow some Schiff’s reagent.

Best wishes,

Sybee

Hi,
This is urgent please reply.

Thank you for the reply. If you do not mind to give me both procedures and materials needed. Also from I can get the needed materials and chemicals. It will be great if you can support it with some explanation because I am not familiar with either one.

Thanks a lot

Malondialdehyde (MDA) is a product of lipid oxidation that is commonly measured to quantitate the reaction. It is usually measured after reaction with thiobarbituric acid [the TBARS assay]. I have attached a method for doing this assay, but you will need some other reagents like trichloroacetic acid or concentrated acetic acid, malondialdehyde to use as a standard and a spectrophotometer to read the absorbance of the colored reaction product.

You [or rather your teacher or school] can buy TBA and MDA from Sigma-Aldrich Chemical Co. http://www.sigmaaldrich.com/catalog/pro ... &region=US

Most labs have trichloroacetic or acetic acid.

You can also buy Schiff’s reagent from Sigma: http://www.sigmaaldrich.com/catalog/sea ... partialmax

Here’s the paper that describes using Schiff’s reagent to measure MDA: https://www.dovepress.com/evaluation-of ... mendation1
Download the free pdf file and look in the Methods section under Colorimetric Assay. It seems simple enough although I have never tried it. The paper measures MDA in a urine sample but it should work for other types of samples. The urine is diluted 1 to 50 in distilled water and 0.01 volumes of the Schiff reagent is added. Here again, you will need a spectrophotometer to measure the absorbance.

If you don’t have access to a spec then you could make a series of standards with pure MDA, react them with Schiff’s and compare the color of your test sample to the standards. This won’t be quantitative, but it will give you an estimate of the MDA concentration.

If you have more questions let me know and i will get back to you right away.

Sybee