Dragendorff’s Reagent
Purpose: Detection of alkaloids in plant extracts or formulations.
Procedure (stock solution method):
Stock A: Dissolve 1.7 g bismuth subnitrate in 20 ml glacial acetic acid.
Stock B: Dissolve 40 g potassium iodide in 100 ml distilled water.
Mix 10 ml of A and 20 ml of B.
Dilute with distilled water to make 100 ml.
Store in a dark bottle; stable for weeks.
DETERMINATION OF CITRIC ACID IN FRUIT JUICE
AIM:
To estimate citric acid content in fruit juice.
APPARATUS:
Burette, conical flask, pipette.
REAGENT:
0.1M NaOH, phenolphthalein.
PRINCIPLE:
Citric acid neutralized by NaOH; endpoint indicated by pink color.
PROCEDURE:
Pipette 10ml of juice into a flask.
Add 2–3 drops phenolphthalein.
Titrate with NaOH to pink endpoint.
CALCULATION:
% Citric Acid = Titre × 0.064 × 100 / Volume of sample
DETECTION OF BORIC ACID IN FOOD
AIM:
To detect boric acid in food samples (e.g., milk, jaggery).
APPARATUS:
Test tubes, turmeric paper.
REAGENT:
None (turmeric paper acts as indicator).
PRINCIPLE:
Boric acid turns turmeric paper red, which turns green on ammonia exposure.
PROCEDURE:
Dip turmeric paper in food extract.
Dry and observe color.
Expose to ammonia vapor for confirmation.
RESULT:
Red to green color change confirms boric acid.
TEST FOR SULPHUR DIOXIDE IN DRIED FRUITS
AIM:
To detect presence of SO₂ preservative in food.
APPARATUS:
Test tubes, beaker.
REAGENT:
Pararosaniline hydrochloride, formaldehyde.
PRINCIPLE:
SO₂ reacts with dye and formaldehyde to form pink/magenta color.
PROCEDURE:
Boil fruit sample in water, cool extract.
Add 2ml dye reagent + formaldehyde.
Observe color change.
RESULT:
Pink color indicates presence of sulphur dioxide.
ALCOHOL DETECTION IN HAND SANITIZERS
AIM:
To determine the presence and concentration of alcohol in hand sanitizer.
APPARATUS:
Test tube, alcohol hydrometer or colorimeter.
REAGENT:
Potassium dichromate + sulfuric acid.
PRINCIPLE:
Alcohol reduces orange dichromate to green chromium ions.
PROCEDURE:
Add 2ml sanitizer to test tube.
Add dichromate reagent.
Shake and observe color change from orange to green.
RESULT:
Color change confirms alcohol; intensity can indicate concentration.
TEST FOR FORMALIN IN MILK
AIM:
To detect formalin (formaldehyde) in milk.
APPARATUS:
Test tube, ice bath.
REAGENT:
Sulfuric acid, ferric chloride.
PRINCIPLE:
Formalin reacts with ferric chloride and acid to give a violet ring.
PROCEDURE:
Take 5ml milk in a test tube.
Add 5ml sulfuric acid with FeCl₃ carefully along the wall.
Observe for a violet ring at the interface.
RESULT:
Presence of violet ring indicates formalin.
TEST FOR PRESENCE OF UREA IN MILK
AIM:
To detect adulteration of milk with urea.
APPARATUS:
Test tubes, dropper.
REAGENT:
Para-dimethylaminobenzaldehyde (PDAB) reagent.
PRINCIPLE:
Urea reacts with PDAB to form a yellow color.
PROCEDURE:
Add 5ml milk sample in a test tube.
Add 2ml of PDAB reagent.
Observe for yellow color development.
RESULT:
Yellow color indicates presence of urea.
DETERMINATION OF PHOSPHATE IN FOOD (VANADOMOLYBDATE METHOD)
AIM:
To determine phosphate content in a food sample.
APPARATUS:
Test tubes, colorimeter.
REAGENT:
Ammonium molybdate, ammonium vanadate, nitric acid.
PRINCIPLE:
Phosphate reacts with vanadomolybdate reagent to form a yellow complex.
PROCEDURE:
Prepare sample extract.
Add reagent and incubate for 10 minutes.
Measure absorbance at 400–420 nm.
CALCULATION:
Compare with phosphate standard curve.
DETERMINATION OF VITAMIN A (COLORIMETRIC METHOD)
AIM:
To determine the vitamin A content in margarine or food sample.
APPARATUS:
Test tubes, colorimeter, pipettes.
REAGENT:
Chloroform, antimony trichloride reagent (Carr-Price reagent).
PRINCIPLE:
Vitamin A reacts with antimony trichloride to form a blue complex, measurable colorimetrically.
PROCEDURE:
Extract sample with chloroform.
Add 2ml of Carr-Price reagent.
Measure absorbance at 620 nm.
Compare with vitamin A standard.
CALCULATION:
Use standard calibration curve to estimate µg vitamin A.
DETERMINATION OF SUGAR IN HONEY (FEHLING’S TEST)
AIM:
To detect reducing sugars in honey.
APPARATUS:
Test tubes, burette, water bath.
REAGENT:
Fehling’s A and B solutions.
PRINCIPLE:
Reducing sugars reduce Cu²⁺ to Cu₂O (red precipitate).
PROCEDURE:
Mix equal volumes of Fehling A and B.
Add honey solution gradually while boiling.
Observe brick-red precipitate.
CALCULATION:
Compare against known glucose standards.
DETERMINATION OF PROTEIN (KJELDAHL METHOD)
AIM:
To determine total protein content in a sample.
APPARATUS:
Digestion flask, distillation unit, titration setup.
REAGENT:
Concentrated H₂SO₄, NaOH, boric acid, indicator.
PRINCIPLE:
Nitrogen is converted to ammonia, distilled, and titrated to estimate protein.
PROCEDURE:
Digest sample with H₂SO₄ + catalyst.
Neutralize, distill ammonia into boric acid.
Titrate with HCl.
CALCULATION:
% Protein = Titre × 1.4 × 6.25 / Sample weight
DETERMINATION OF ALCOHOL IN WINE (DISTILLATION + DENSITY)
AIM:
To measure ethanol content in wine.
APPARATUS:
Distillation setup, pycnometer or alcohol hydrometer.
REAGENT:
None.
PRINCIPLE:
Ethanol is distilled and measured based on density.
PROCEDURE:
Distill 100ml of wine.
Collect distillate and measure density at 20°C.
Refer to alcohol tables.
CALCULATION:
% Alcohol = Based on density from standard chart.
CALCIUM TEST IN MILK (EDTA TITRATION)
AIM:
To estimate calcium content in milk.
APPARATUS:
Burette, pipette, conical flask.
REAGENT:
0.01M EDTA, buffer solution (pH 10), Eriochrome Black T.
PRINCIPLE:
EDTA binds calcium ions in presence of indicator, forming a color change at endpoint.
PROCEDURE:
Pipette 10ml of milk (diluted), add buffer and indicator.
Titrate with EDTA until the wine-red color changes to blue.
CALCULATION:
mg Ca²⁺ = Titre value × 40.08 (molar mass of Ca)
ASH CONTENT TEST IN FLOUR
AIM:
To determine the inorganic (mineral) content in flour.
APPARATUS:
Crucible, furnace, balance.
REAGENT:
None.
PRINCIPLE:
Organic matter is burnt off, leaving behind ash (mineral content).
PROCEDURE:
Weigh 5g of flour in a crucible.
Incinerate in furnace at 550°C for 4 hours.
Cool in desiccator and weigh.
CALCULATION:
% Ash = (Weight of ash / Weight of sample) × 100
Molisch’s Reagent
Purpose: A general test for carbohydrates.
Procedure:
Dissolve 5 g of α-naphthol in 100 ml of ethanol (95%).
Store in a dark bottle.
pH TEST OF SOFT DRINKS
AIM:
To measure the pH level of a soft drink.
APPARATUS:
pH meter or pH paper, beaker.
REAGENT:
None (or universal indicator).
PRINCIPLE:
pH indicates the acidity or alkalinity of a solution.
PROCEDURE:
Pour 10ml of the soft drink into a beaker.
Dip pH paper or insert pH meter electrode.
Record the pH value.
RESULT:
Soft drinks usually show pH between 2.5 – 4.5.
STARCH TEST IN FOODS (IODINE TEST)
AIM:
To detect the presence of starch in food items.
APPARATUS:
Test tube, dropper, beaker.
REAGENT:
Iodine solution.
PRINCIPLE:
Iodine reacts with starch to form a blue-black complex.
PROCEDURE:
Add a few drops of iodine solution to the food solution or crushed sample.
Observe for a blue-black coloration.
RESULT:
Presence of starch is confirmed by blue-black color.
FAT CONTENT TEST (SOLVENT EXTRACTION METHOD)
AIM:
To determine the fat content in a food sample.
APPARATUS:
Soxhlet extractor (or simple filter, beaker), drying oven, balance.
REAGENT:
Petroleum ether or hexane.
PRINCIPLE:
Fat is soluble in organic solvents and can be extracted and weighed.
PROCEDURE:
Weigh 5g of dried sample.
Extract fat using ether in a Soxhlet setup or soak in solvent.
Evaporate solvent and weigh the remaining fat.
CALCULATION:
% Fat = (Weight of extracted fat / Weight of sample) × 100
Simulated Saliva Fluid
Purpose: Used for evaluating drug dissolution in the oral cavity.
Procedure:
Dissolve 0.4 g NaCl, 0.4 g KCl, 0.795 g CaCl₂·2H₂O, and 0.69 g NaH₂PO₄·2H₂O in 900 ml distilled water.
Adjust pH to 6.8 with NaOH.
Make up the volume to 1000 ml with distilled water.
Store at room temperature.
Simulated Intestinal Fluid (SIF)
Purpose: Mimics the environment of the small intestine to test drug stability, dissolution, and release.
Procedure:
Weigh 6.8 g of monobasic potassium phosphate (KH₂PO₄).
Dissolve in 250 ml of distilled water.
Add 77 ml of 0.2 N NaOH.
Add 10 g of pancreatin.
Dilute to 1000 ml with distilled water.
Mix well and adjust pH to 6.8 ± 0.1.
Filter if necessary before use.
