Pharmacognosy 3 rd Class 2 nd Semester Lab

Pharmacognosy 3 rd Class, 2 nd Semester Lab. 6 Identification Of Caffeine Crystals

Identification of Caffeine Crystals Qualitative analysis Chromatography TLC Quantitative analysis By weight the crystals of the caffeine Chemical test The muroxide test

Qualitative analysis 1) Specific Test The Muroxide test Aim: - To identify the caffeine alkaloid (Purine alkaloid) from other alkaloids. Equipments and reagents: ØPorcelain dish ØWater bath ØPotassium chlorate ØConcentrated HCL ØAmmonia vapor Procedure: § Take few crystals of caffeine in porcelain. § Add small amount of potassium chlorate (KCLO 3). § Add 2 drops of concentrated HCL. § Evaporate to dryness. § Expose to ammonia vapor. Result: A purple color is produced and other Purine derivative.

2) TLC Aim: - Used to identify quantitatively the Purine alkaloids. Equipments and reagents: ØGlass jar with its cover ØSilica gel plates ØStandard reagent ØMobile phase (acetone; water; ammonia (90; 7; 30) ØSpray reagent (I/KI) ØCapillary tube Procedure: § Prepare the mobile phase and put in the glass jar, cover the jar and leave it for 45 min. for saturation. § Apply the sample and the standard by the use of capillary tube on the silica gel plate. § Leave the plate in the jar until the solvent reaches 3/4 of the plate. Remove the plate, dry, and then spray with the spraying reagent. § Calculate RF Value.