What other methods can be used to rule out the effect of experimental conditions on vitamin C conten

1) In order to accurately measure the vitamin C content, what operation steps should be paid attention to during the experimentA: 1When measuring the liquid, it must be accurate, and pay attention to the line of sight when reading, which must be at the same level as the lowest part of the liquid concave level;

2.When titrating, the titration speed must be controlled, do not drop too much 2,6-dichlorophenol indifol solution at once, resulting in excessive titration.

3.During the titration process, attention should be paid to the color of the solution in the Erlenmeyer flask, and the titration endpoint should be accurately judged, that is, the reddish color can be maintained for 15 seconds without fading, and the reddish color at the end point of each titration should be the same standard, that is, the degree of redness should be the same.

Test name: compare the content of vitamin C in different vegetables or fruits 1. Purpose requirements: 1. Use scientific methods to compare the content of vitamin C in different vegetables or fruits 2. Gradually develop the habit of thinking about the problem carefully in the process 2. Experimental equipment:

For reference) Materials: green peppers, bok choy, tomatoes, spinach, potatoes, celery, chrysanthemum and other vegetables; Apples, sweet oranges (or oranges), grapes, nectarines, pears, watermelons and other fruits Utensils: juicer (or mortar), beaker, test tube, dropper, gauze, absorbent paper, water, potassium permanganate solution 3. Experimental principle:

Vegetables and fruits contain vitamin C The content of vitamin C in different fruits and vegetables is different Vitamin C has a wonderful property - its aqueous solution can fade the potassium permanganate solution, and the higher the vitamin C content in fruits and vegetables, the less amount of vegetable juice or juice dripped According to this characteristic, we can determine the amount of vitamin C in vegetables or fruits Fourth, the experimental plan: (1) Inspection equipment (2) Squeezing fruit juice and vegetable juice (3) Solution fading test 5. Experimental operation: (1), First of all, the test tube is numbered

2), in each of the 2 test tubes loaded with 2 ml of the same amount of potassium permanganate solution (3), take a clean, dry small dropper to absorb the apple juice, drop drop into the No. 2 test tube drop, drip, side by side, while observing, until the potassium permanganate fades color, record the number of drops; Then use the same small dropper, clean it in clean water, and use absorbent paper to absorb the water inside and outside the dropper Take the kiwifruit juice and drop it into the No. 3 test tube, and the operation method is the same as the No. 2 test tube, record the number of drops Finally, compare the number of drops in No. 1 and No. 2 test tubes: the vitamin C content of more drops is less, and the vitamin C content of fewer drops is more Sixth, record the data and draw conclusions: Choose two kinds of fresh vegetables or fruits Potassium permanganate solution The number of drops of vegetable juice or juice drops Experimental conclusion Kiwifruit juice No. 1 test tube:

2ml 8 drops Kiwi juice contains more vitamin C Apple juice No. 2 tube: 2ml 14 drops.

Vitamin C is acidic, has strong reducing properties, is easy to oxidize and decompose when heated or in solution, and is more easily oxidized under alkaline conditions.

Structural characteristics: Vitamin C is composed of carbon, hydrogen and oxygen.

Composition: A vitamin molecule is made up of six carbon atoms, eight hydrogen atoms, and six oxygen atoms.

Principle and method of identification of vitamin C 1 Structure and properties acidic: Vitamin C is generally manifested as a monobasic acid, which is more acidic. Reducibility:

Vitamin C has a dienol structure in its structure, which is strongly reducible. It can undergo redox reaction with silver nitrate, 2,6-dichloroindiphenol and iodine. 2 Content determination (1) direct iodine dosing.

The determination of vitamin C is the determination of copy vitamin C. Among the national standard methods for the determination of vitamin C, the fluorescence method is the first standard method for determining the content of vitamin C in food, and the dinitrophenylhydrazine method is used as the second method.

Precautions. Most plant tissues contain an oxidase that destroys ascorbic acid, so ascorbic acid should be measured using fresh samples and homogenizing samples with metaphospho-acetic acid extract as soon as possible to preserve vitamin C.

Some samples with high pectin content are not easy to filter, so they can be filtered by suction filtration, or centrifugation can be done first, and then the supernatant can be taken for filtration.

Activated carbon can oxidize ascorbic acid to dehydroascorbic acid, but it also has the effect of adsorbing ascorbic acid, so the dosage of activated carbon should be appropriate and accurate, so the balance should be weighed. Our experimental results proved that the reduced ascorbic acid in the measured sample could be completely oxidized to dehydrogenation with 2g of activated carbon, and its adsorption effect was not obvious.

The color of potassium permanganate solution is purple, vitamin C can fade potassium permanganate solution, add the same amount of fruit juice in the test tube, add potassium permanganate solution dropwise, while dripping**, while observing, the less it is dropped, the lower the vitamin C contained in the fruit juice, and the higher it is Therefore, the aqueous solution of vitamin C can be used to fade the potassium permanganate solution to detect the content of vitamin C in food

So the answer is: potassium permanganate solution; Fade.