Lesson 10. Assay of Ascorbic Acid Tablets

Vitamin C

Assay of Ascorbic Acid is commonly performed using commercially available tablets of ____________________.

non-chewable, uncoated, white

The assay uses _________________________ Ascorbic Acid Tablets.

residual method

The ascorbic acid assay employs a a.________________________ known as b.__________. It is a redox method where a sample of analyte is made to react with a source of c.______, and the excess Br2 is back-titrated with a solution of d.___________________.

a = ?

bromination

The ascorbic acid assay employs a a.________________________ known as b.__________. It is a redox method where a sample of analyte is made to react with a source of c.______, and the excess Br2 is back-titrated with a solution of d.___________________.

b = ?

Br2

The ascorbic acid assay employs a a.________________________ known as b.__________. It is a redox method where a sample of analyte is made to react with a source of c.______, and the excess Br2 is back-titrated with a solution of d.___________________.

c = ?

Na2S2O3

The ascorbic acid assay employs a a.________________________ known as b.__________. It is a redox method where a sample of analyte is made to react with a source of c.______, and the excess Br2 is back-titrated with a solution of d.___________________.

d = ?

accuracy of the label

The ascorbic acid assay is useful to check the ___________________ claim for commercially available Ascorbic acid tablets (500 mg).

expired

Ascorbic Acid Assays can be used to determine whether the drug is a.________ (less than 90% API) or is a b.__________________ (less than 80% API).

a = ?

counterfeit

Ascorbic Acid Assays can be used to determine whether the drug is a.________ (less than 90% API) or is a b.__________________ (less than 80% API).

b = ?

5 ascorbic acid tablets

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

1 = ?

0.4 to 0.5 g of the powdered tablet

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

2 = ?

50 mL of 1.5M H2SO4

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

3 = ?

5 g KBr

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

4 = ?

KBrO3

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

5.a. = ?

faint yellow

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

5.b. = ?

volume

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

6 = ?

3 g of KI

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

7 = ?

5 mL of starch T.S

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

8 = ?

Na2S2O3

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

9.a. = ?

disappearance of the blue

Ascorbic Acid Assay Procedure:

1. Weigh ____________________ and pulverize them thoroughly in a mortar.

2. Weigh accurately _________________________ sample in an iodine flask.

3. Dissolve the sample in ____________________________.

4. Add __________ to the sample solution.

5. Titrate immediately with standard a._________ solution to the first b._______ color due to excess bromine.

6. Record _________ of standard KBrO3 solution used

7. Add _____________.

8. Add _________________.

9. Back-titrate with standard a.____________ solution to the b._____________ color.

9.b. = ?

KBr and KBrO3

Ascorbic Acid Assay Procedure:

• H2SO4 makes the environment acidic, which hydrolyzes a.____________, liberating b.___________________. It also acts as a c._______________.

a = ?

Bromine

Ascorbic Acid Assay Procedure:

• H2SO4 makes the environment acidic, which hydrolyzes a.____________, liberating b.___________________. It also acts as a c._______________.

b = ?

catalyst

Ascorbic Acid Assay Procedure:

• H2SO4 makes the environment acidic, which hydrolyzes a.____________, liberating b.___________________. It also acts as a c._______________.

c = ?

source of Bromine

Ascorbic Acid Assay Procedure:

• KBr acts as an additional ___________________

additional source of Br2

Ascorbic Acid Assay Procedure:

• role of KBrO3

orange solution

Ascorbic Acid Assay Procedure:

• overstep

source of iodine

Ascorbic Acid Assay Procedure:

• KI serves as a _________________ and forms a blue-black or deep blue starch-iodo complex.

starch-iodo complex is broken

Ascorbic Acid Assay Procedure:

• When Sodium Thiosulfate reacts with Iodine, the ____________________ causing the blue-black coloration to disappear

bromination

There are 4 chemical reactions involved, and the first and second reactions are part of the a.____________ process. Meanwhile, the third and fourth reactions are what happen during b.___________________________.

a = ?

back-titration with sodium thiosulfate

There are 4 chemical reactions involved, and the first and second reactions are part of the a.____________ process. Meanwhile, the third and fourth reactions are what happen during b.___________________________.

b = ?

Chemical Reaction #1

Bromate (from KBrO3) and Bromine (from KBr)

CHEMICAL REACTION (1ST RXN)

a.______________________________________ are reacted in an b._______ environment to aid the formation of molecular c.________. Overall, it shows the d.______________________.

a = ?

acidic

CHEMICAL REACTION (1ST RXN)

a.______________________________________ are reacted in an b._______ environment to aid the formation of molecular c.________. Overall, it shows the d.______________________.

b = ?

Bromine

CHEMICAL REACTION (1ST RXN)

a.______________________________________ are reacted in an b._______ environment to aid the formation of molecular c.________. Overall, it shows the d.______________________.

c = ?

liberation of Bromine

CHEMICAL REACTION (1ST RXN)

a.______________________________________ are reacted in an b._______ environment to aid the formation of molecular c.________. Overall, it shows the d.______________________.

d = ?

Chemical Reaction #2

oxidizing agent

CHEMICAL REACTION (2ND RXN)

Molecular bromine (a._____________) reacts with ascorbic acid, an antioxidant (aka b.______________). This forms c._______________, the oxidized form of ascorbic acid. Oxidation is also known as d.____________. Since ascorbic acid was oxidized, it involves the principle of e._____________.

a = ?

reducing agent

CHEMICAL REACTION (2ND RXN)

Molecular bromine (a._____________) reacts with ascorbic acid, an antioxidant (aka b.______________). This forms c._______________, the oxidized form of ascorbic acid. Oxidation is also known as d.____________. Since ascorbic acid was oxidized, it involves the principle of e._____________.

b = ?

dehydroascorbic acid

CHEMICAL REACTION (2ND RXN)

Molecular bromine (a._____________) reacts with ascorbic acid, an antioxidant (aka b.______________). This forms c._______________, the oxidized form of ascorbic acid. Oxidation is also known as d.____________. Since ascorbic acid was oxidized, it involves the principle of e._____________.

c = ?

dehydrogenation

CHEMICAL REACTION (2ND RXN)

Molecular bromine (a._____________) reacts with ascorbic acid, an antioxidant (aka b.______________). This forms c._______________, the oxidized form of ascorbic acid. Oxidation is also known as d.____________. Since ascorbic acid was oxidized, it involves the principle of e._____________.

d = ?

VILEORA

CHEMICAL REACTION (2ND RXN)

Molecular bromine (a._____________) reacts with ascorbic acid, an antioxidant (aka b.______________). This forms c._______________, the oxidized form of ascorbic acid. Oxidation is also known as d.____________. Since ascorbic acid was oxidized, it involves the principle of e._____________.

e = ?

Chemical Reaction #3

molecular bromine

CHEMICAL REACTION (3RD RXN)

• Excess a.____________ reacts with b.__________ to form c.__________ and d._________________.

a = ?

iodide ions

CHEMICAL REACTION (3RD RXN)

• Excess a.____________ reacts with b.__________ to form c.__________ and d._________________.

b = ?

bromide ions

CHEMICAL REACTION (3RD RXN)

• Excess a.____________ reacts with b.__________ to form c.__________ and d._________________.

c = ?

molecular iodine

CHEMICAL REACTION (3RD RXN)

• Excess a.____________ reacts with b.__________ to form c.__________ and d._________________.

d = ?

Chemical Reaction #4

liberated iodine

CHEMICAL REACTION (4TH RXN)

The a.________________ from the previous reaction reacts with the standard b._____________________ to produce c.___________________.

a = ?

sodium thiosulfate

CHEMICAL REACTION (4TH RXN)

The a.________________ from the previous reaction reacts with the standard b._____________________ to produce c.___________________.

b = ?

tetrathionate and iodide

CHEMICAL REACTION (4TH RXN)

The a.________________ from the previous reaction reacts with the standard b._____________________ to produce c.___________________.

c = ?