C. You are asked to measure the levels of the antioxidants BHT, benzoic acid and

Question

C. You are asked to measure the levels of the antioxidants BHT, benzoic acid and ascorbic acid in a prepared meal. In order to do this the meal is first homogenized, then a 50.2g sample is freeze dried resulting in a dry weight of 10.7g. A 2.4g portion of the freeze- dried meal homogenate is dissolved in 20.0mL of water in a separating funnel. This solution is shaken with 20.0mL of octanol and left to separate into 2 layers. For each antioxidant, give an explanation for which layer (upper or lower) it primarily resides in The concentration of benzoic acid in the upper layer is found to be 0.15mg/mL. What is the total amount of benzoic acid in the initial 50.2g sample of the meal? a. b. The octanol-water partition coefficient logPow for the antioxidants BHT, benzoic acid and ascorbic acid 5.1, 1.87 and -1.85 respectively and the density of octanol is 0.82g/mL.

Explanation / Answer

a) Benzoic acid: Lower layer (aqeous layer) and upper layer both

Ascorbic acid: Lower layer (aqeous layer)

BHT : upper layer (octanol)

b) Given : 1mL of octanol contains 0.15mg

So amount of benzoic acid in 20mL = 20 X 0.15 = 3mg

We have taken 2.4g of frozen portion contains 3mg

So 1g must have = 3mg / 2.4 = 1.25mg

So 10.7 grams will have = 1.25 X 10.7 mg = 13.375 mg

The 10.7 grams freezed was obtained from 50.2g meal

So amount of benzoic acid in 50.2g of meal = 13.375 mg

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