Third Stage Inorganic Pharmaceutical Chemistry Lab 5 PDF

Third stage Inorganic Pharmaceutical Chemistry Assay of Sodium Benzoate Assay of Citric Acid Lab. 5 Assist. lecturer Abdul Muhaimen altaee M.Sc. pharmaceutical chemistry Assay of Sodium Benzoate - + ❑Introduction Sodium...

Third stage Inorganic Pharmaceutical Chemistry Assay of Sodium Benzoate Assay of Citric Acid Lab. 5 Assist. lecturer Abdul Muhaimen altaee M.Sc. pharmaceutical chemistry Assay of Sodium Benzoate - + ❑Introduction Sodium benzoate (C7H5NaO2, m. wt.= 144.1) is a white, crystalline or granulated powder. It is slightly hygroscopic, freely soluble in water, and sparingly soluble in alcohol. The powder when dried contains not less than 99 % of sodium benzoate. Synthesis of Sodium benzoate It can be produced by neutralizing benzoic acid with sodium hydroxide. C6H5COOH + NaOH C6H5COONa + H2O Sodium benzoate can also be prepared by adding benzoic acid to a hot concentrated solution of sodium bicarbonate until effervescence stops. The solution is then evaporated, cooled, and allowed to crystallize (or evaporate to dryness), and then granulated. C6H5COOH + NaHCO3 C6H5COONa + H2CO3 Physical properties 1-It is a white crystalline powder. 2-Density(1.44). 4-Melting point >300°C. 5-Odourless compound that has a sweet. 6-Free soluble in water (1gm/ 2mL water). Chemical properties 1-Sodium benzoate and ascorbic acid (vitamin C) combine to form benzene. Although most beverages containing both ingredients have benzene levels below the WHO's danger limit (5ppb), heat and light can increase the rate of benzene formation. Benzene is a known carcinogen and can cause anemia due to its damaging effects on bone marrow. 2-When sodium benzoate is heated with soda-lime (a mixture of sodium hydroxide NaOH and calcium oxide CaO) and undergoes decarboxylation, benzene is produced. 3-Sodium benzoate reacts with hydrochloric acid to produce benzoic acid. C6H5COONa + HCl NaCl + C6H5COOH Pharmaceutical applications 1- Sodium benzoate has antibacterial and antifungal properties and is used as a preservative in the pharmaceutical formulation including oral preparation in concentrations up to 0.5 %. It is also a common ingredient in cough preparations. 2- Sodium benzoate is used as a treatment for urea cycle disorders due to its ability to bind amino acids. This leads to excretion of these amino acids and a decrease in ammonia levels. 3- Sodium benzoate may be used in the therapy of schizophrenia. 4- Sodium benzoate is used in cosmetic products like mouthwash, toothpaste, deodorant, lotion, and shampoo. Assay of Sodium Benzoate ❑ Chemical principle Sodium benzoate is a salt derived from a weak acid and a strong base, so its aqueous solution is alkaline. Therefore, solutions containing sodium benzoate are assayed using a standard N/2 hydrochloric acid solution in an acid-base titration. COONa COOH + HCl + NaCl sodium benzoate benzoic acid procedure ▪ fill the burette with N/2 HCl to a level (adjust it) ▪put 10 mL of an unknown sodium benzoate solution in a clean conical flask ▪ add 25 mL of D. W. and 15 mL of ether ▪ add 6 drops of bromophenol blue (BPB) ▪start titration by adding HCl dropwise with shaking the aqueous and ethereal layers until a light green color persists in the aqueous layer (endpoint) ▪ record the volume of HCl used Assay of Sodium Benzoate ❑ titration apparutus Assay of Sodium Benzoate start point end point (violet - blue) (bluish green) Assay of Sodium Benzoate ❑calculations the chemical factor: (each 1 mL of N/2 hydrochloric acid is equivalent to 0.07205 g of C7H5NaO2) correct the volume of HCl solution used into N/2 volume calculate the quantity of sodium benzoate present in your sample Homework Why do we add ether in the titration of sodium benzoate with HCl? How does sodium benzoate work as a preservative? Assay of Citric Acid Assay of Citric Acid ❑Introduction The citric acid (C6H8O7, m. wt. = 192.09) is a white crystalline powder (colorless crystals). It is very soluble in water and freely soluble in alcohol. It is a tri-basic acid, so its solutions are strongly acidic. It is available in the anhydrous form or monohydrate form. The assay of citric acid is based on the anhydrous form. Uses of citric acid Citric acid is widely used in the food and drinks industry due to its sour taste. It also acts as a preservative in frozen foods. Its effervescence property makes it a common ingredient in gaseous soft drinks. Applications in pharmaceutical preparations, such as suspension and elixir dosage forms to maintain the stability of API & and improve the effect of preservatives. In cosmetic formulations as PH adjustment and in cooperation with antioxidant systems. Assay of Citric Acid ❑ Chemical principle Since citric acid has strong acid properties, it is titrated against a standard basic solution like N/1 NaOH solution in an acid-base reaction. Assay of Citric Acid ❑ procedure Weigh accurately 1 g of citric acid (or you may take 10 mL of an unknown citric acid solution), dissolve in 20 ml of distilled water, and titrate with N/1 sodium hydroxide solution using 2 drops of phenolphthalein solution as the indicator. Titrate until you get a faint pink color. Assay of Citric Acid ❑ titration apparutus Assay of Citric Acid ❑calculations the chemical factor: (each 1 mL of N/1 sodium hydroxide solution is equivalent to 0.06403 g of C6H8O7) correct the volume of NaOH solution used into N/1 volume calculate the quantity of citric acid present in your sample Homework Q/ 10 ml of unknown citric acid solution were assayed the volume of NaOH used in the titration of citric acid is 8ml and the volume for 1N NaOH is 5ml calculate: 1) The Normality of 8ml NaOH 2) %W/v citric acid If you know that the chemical factor is 0.06403g