Basic Principles, Methods and Application of Diazotization Titration : Pharmaguideline -->

Editable Pharmaceutical Documents in MS-Word Format


Basic Principles, Methods and Application of Diazotization Titration

Diazonium compounds are formed by disintegrating primary aromatic amines into diazo compounds. The synthetic dye industry used this process in 1853.
Diazonium compounds are formed by disintegrating primary aromatic amines into diazo compounds. The synthetic dye industry used this process for the first time in 1853. Peter Griessin is credited with proposing the mechanism of this process. An aromatic amine reacts to form a diazonium salt in an acidic medium by reacting with sodium nitrite. Dye is the first substance to be measured using this technique.


This method involves reacting sodium nitrite with the aromatic primary amine in the sample to turn it into diazonium salt.

R − NH2 + NaNO2 +HCl🡪   R − N+ ≡ N − Cl + NaCl + H2O

A solution of amine is added to an acid solution at 0-5 °C accompanied by the addition of sodium nitrite. A reaction between the amine and nitrous acid results in the formation of nitrosamine, followed by tautomerization, which results in the water being lost. In diazonium, positive charges are displaced at ortho and para positions to stabilize the ions.

C6H5NH2 + NaNO2 + HCl    C6H5N = NCl + NaCl + H2O


The reaction between sodium nitrite and hydrochloric acid produces sodium chloride and nitrous acid.

NaNO2 + HCl  NaCl + HNO2

As a result of the reaction between the nitrous acid and the aromatic amine, the diazonium salt is obtained. In addition to nitrous acid, ammonium sulfate solution is added to remove excess nitrous acid.

R − NH2 + HNO2🡪    R − N = NH + H2O

Starch iodide paper produces a blue color when it comes into contact with the endpoint. To prepare this solution, mix starch mucilage with potassium iodide and soak the filtered paper in it.

KI + HCl  KCl + HI

2HI + 2HNO2🡪   I2 + 2NO =2H2O

I2 + starch mucilage 🡪   blue colour end point


Following the transfer to the standard flask, the sample is weighed and processed as described above. Secondly, distilled water is added, followed by concentrated hydrochloric acid and potassium bromide. A standard solution is thereby formed. Pipette the standard solution out at the appropriate volume and maintain the temperature between 0 and 5 degrees Celsius. A sodium nitrite solution is then added to the solution and titrated until the starch iodide paper turns blue. Another procedure involves immersing the platinum electrodes after maintaining the flask's temperature. Once the electrodes are connected to the potentiometer, sodium nitrite solution is titrated slowly until a permanent deflection can be observed at the endpoint.


1. Sulphonamides are determined using this method.
2. Weigh a sample of 1 mg of sulphonamide accurately and dissolve it in 4ml of concentrated HCl and 10ml of distilled water. The 0.1 M Solution of Sodium Nitrite solution is then titrated with this solution after cooling to 15 °C. After one drop of the solution has been streaked on the starch iodide paper, until the blue color appears, you know you have reached the endpoint. Based on the following equation, the percentage content of the sulpha drug is determined:

This formula requires V to be the volume of the titrant consumed; M to be the molarity of the titrant; EW to be the weight of equivalent drug; W to be the weight of the sample.
3. Applied to the determination of chlorpheniramine.
4. To the five ml of HCl and the fifty ml of distilled water, the accurately weighed sample is added. After cooling the solution to 15°C, it is absorbed. Using starch iodide paper as an indicator, the solution is then titrated with the sodium nitrite solution at 0.1 N.
5. This is used to determine the amount of dopamine in a sample.
6. Procaine is determined with this substance.
7. Amphetamine is determined by using this reaction.
8. Procaine is determined by using this test.
9. For determining ephedrine.
10. This test is used in determining how much P-amino benzoic acid (vitamin B4) is present in food.
11. Method: Add 3 ml of HCl to 5 ml of distilled water after the accurately weighed sample is weighed. This solution is then cooled to 15 degrees Celsius. After the solution has been slowly titrated with sodium nitrite solution, starch iodide paper is used as an indicator to evaluate the titration.
12. The salt nitrate solution of 0.1 N with 0.01371 g of vitamin B4 is equal to 1 ml
Get subject wise printable pdf documentsView Here

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
.moc.enilediugamrahp@ofni :liamENeed Help: Ask Question

No comments: Read Comment Policy ▼

Post a Comment

Please don't spam. Comments having links would not be published.

Online Courses

Popular Categories

QA SOPs QC SOPs Micro SOPs HVAC Production SOPs Stores SOPs Checklists Maintenance SOPs HPLC Sterile GLP Validation Protocols Water System GDP Regulatory Maintenance Calibration Warning Letters Education B.Pharmacy
Online Courses

Follow Pharmaguideline



Editable Pharmaceutical Documents in MS-Word Format. Ready to use SOPs, Protocols, Master Plans, Manuals and more...




Pharmaceutical Updates

✔ Worldwide Regulatory Updates
✔ Pharmaceutical News Updates
✔ Interview Questions and Answers
✔ All Guidelines in One Place


Recent Posts