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To determine the concentration of the serum by Liebermann-Burchard colorimetric method. Mathod of preparation in easy step and in easy language to learn reagent are Reagents are absolute alcohol, diethyl ether, acetic anhydride, standard solution of cholesterol.

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Liebermann-Burchard colorimetric method cholesterol serum preparation procedure

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Liebermann-Burchard method preparation reagent procedure steps

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Now I have enough from both the textbook and my base knowledge to give you a thorough, easy-to-understand guide. Here is the complete method:

Liebermann-Burchard Colorimetric Method - Serum Cholesterol Estimation

What is This Test?

This method measures the total cholesterol concentration in serum. Cholesterol, when treated with acetic anhydride and sulfuric acid in an anhydrous (water-free) environment, produces a blue-green color. The darker the color, the higher the cholesterol. You compare your unknown sample to a known standard to calculate the concentration.

Principle (in simple words)

Cholesterol + Acetic Anhydride + Sulfuric Acid → Blue-green colored compound
The color is measured at 620 nm using a colorimeter/spectrophotometer. The amount of color is directly proportional to the amount of cholesterol.

Reagents You Need

ReagentPurpose
Absolute alcohol (ethanol)Dissolves serum lipids; removes water
Diethyl etherExtracts cholesterol from serum
Acetic anhydridePart of the color-developing reagent
Standard cholesterol solutionKnown concentration for comparison
Concentrated sulfuric acid (H₂SO₄)Part of the L-B reagent (color developer)
Glacial acetic acidOften added as a diluent/stabilizer
Note: Although not listed in your reagents, concentrated sulfuric acid is required to develop the color - it is always part of the L-B reagent. Glacial acetic acid is also typically used.

Preparation of Reagents - Step by Step

Step 1 - Prepare the Liebermann-Burchard (L-B) Reagent

This is the most important reagent. It must be made carefully and kept ice-cold and away from moisture.
What you need:
  • 1 part acetic anhydride
  • 1 part glacial acetic acid (if using)
  • Small amount of concentrated sulfuric acid (added last, drop by drop)
How to make it:
  1. Take a clean, dry glass tube or flask. Moisture ruins this reagent.
  2. Add 10 parts acetic anhydride into the tube. Keep it in an ice bath.
  3. Slowly and carefully, add 1 part concentrated sulfuric acid drop by drop while mixing gently.
  4. The mixture will heat up - this is normal. Keep cooling in ice.
  5. The final reagent should be clear and colorless.
  6. Use it fresh - prepare it just before use, or store in the dark at 4°C for a short time.
Safety tip: Always add acid to anhydride, never anhydride to acid. Keep away from water.

Step 2 - Prepare the Standard Cholesterol Solution

This gives you a known reference to calculate your unknown concentration.
Stock Standard (1 mg/mL or 200 mg/dL):
  1. Weigh out 100 mg of pure cholesterol accurately.
  2. Dissolve in absolute alcohol in a 100 mL volumetric flask.
  3. Make up to 100 mL with absolute alcohol. This gives 1 mg/mL.
Working Standard (for calibration curve):
  • Dilute the stock in absolute alcohol to make concentrations like: 50, 100, 150, 200, 250 mg/dL.
  • Use these to plot a calibration graph.

Step 3 - Prepare the Serum Sample (Extraction)

Cholesterol must first be extracted out of the serum before the color reaction.
  1. Take 0.1 mL of serum in a clean, dry test tube.
  2. Add 2 mL of absolute alcohol - this precipitates proteins and releases lipids.
  3. Mix well and centrifuge for 5 minutes (or filter).
  4. Take the clear supernatant (alcoholic extract).
Some methods use a diethyl ether-alcohol mixture (3:1) for better extraction of cholesterol esters.

Step 4 - Color Development (The Reaction)

This is where the cholesterol reacts to form the green color.
  1. Take the clear extract (0.5 or 1 mL) in a clean dry tube.
  2. Allow alcohol/ether to evaporate completely (or use a water bath at 37°C) - the tube must be completely dry.
  3. Dissolve the residue in 2 mL of glacial acetic acid.
  4. Add 2 mL of freshly prepared L-B reagent (acetic anhydride + H₂SO₄).
  5. Mix gently and let stand at room temperature (25°C) for 30-35 minutes in the dark.
  6. The solution turns blue-green.
Do not expose to light during incubation - it affects the color.

Step 5 - Measurement

  1. Read absorbance at 620 nm (or 640 nm) in a colorimeter or spectrophotometer.
  2. Use a reagent blank (all reagents but no sample) to zero the instrument.
  3. Run the standard alongside the test.

Calculation

$$\text{Cholesterol (mg/dL)} = \frac{\text{Absorbance of Test}}{\text{Absorbance of Standard}} \times \text{Concentration of Standard (mg/dL)}$$

Setting Up the Tubes - Quick Reference Table

TubeSerumStandardAbsolute AlcoholL-B Reagent
Blank--0.5 mL2 mL
Standard-0.5 mL-2 mL
Test0.1 mL serum extract--2 mL

Key Points to Remember

  • No water anywhere - water gives a brown/turbid color and ruins the test.
  • Temperature matters - do the reaction at 25°C. Higher temperature speeds up color fading.
  • Time matters - read between 30-35 minutes at 25°C (color fades after ~40 minutes).
  • Make L-B reagent fresh each time if possible.
  • Protect from light during color development.
  • Normal serum cholesterol: 150-200 mg/dL (desirable range).

Why This Method Uses These Reagents

ReagentWhy it's used
Absolute alcoholRemoves water from serum; precipitates proteins; dissolves cholesterol
Diethyl etherBetter lipid extraction; more complete recovery of cholesterol esters
Acetic anhydrideReacts with cholesterol to form the colored compound
Standard cholesterolKnown reference point for calculating unknown concentration
H₂SO₄ (sulfuric acid)Catalyst for the color reaction; produces the characteristic green color
This method, while largely replaced by enzymatic methods in modern labs (as noted in Henry's Clinical Diagnosis and Management by Laboratory Methods), remains the classical reference technique and is still taught and used in teaching labs and resource-limited settings. The Abell-Kendall modification (using this same L-B reagent) is still recognized by the CDC as the reference standard.

Make a flowchart poster of the complete procedure steps

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Liebermann-Burchard Flowchart Poster
Here is your flowchart poster for the Liebermann-Burchard colorimetric method. It covers all 7 steps in sequence:
  1. Prepare L-B Reagent - acetic anhydride + H₂SO₄ in ice bath
  2. Prepare Standard Cholesterol Solution - stock and working dilutions
  3. Extract Serum Sample - alcohol precipitation + centrifuge
  4. Evaporate Solvent - completely dry tube
  5. Color Development - add L-B reagent, incubate 30-35 min at 25°C in dark
  6. Measure Absorbance - read at 620 nm
  7. Calculate Concentration - using the standard formula
Key safety/technical reminders (no water, temperature, timing, light protection) are highlighted as well. You can save or print this image directly for study or lab use.

To determine the polaride content in urine, the reagents are standard silver nitrate solution, standard potassium thiocyanate solution, ferric ammonium sulfate, and concentrated nitric acid. How is the process proceeded to make a flow chart representing all such like you have made upper case of the experiment of cholesterol, same as that flow chart.

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Volhard method chloride determination urine silver nitrate potassium thiocyanate ferric ammonium sulfate procedure steps

To determine the colaride content in urine, the reagents are standard silver nitrate solution, standard potassium thiocyanate solution, ferric ammonium sulfate, and concentrated nitric acid. How is the process proceeded to make a flow chart representing all such like you have made upper case of the experiment of cholesterol, same as that flow chart.

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Volhard's Method Flowchart Poster
Here is your flowchart poster for the Volhard's Back-Titration Method for chloride determination in urine - styled exactly like the cholesterol poster.
Here is a quick summary of all 7 steps shown in the poster:
StepAction
1Collect urine sample + dilute with distilled water
2Acidify with conc. HNO₃ (prevents Fe³⁺ hydrolysis)
3Add known excess standard AgNO₃ → AgCl white precipitate forms
4Filter AgCl OR add nitrobenzene to protect it from back-reaction
5Add ferric ammonium sulfate as indicator (Fe³⁺)
6Back-titrate excess Ag⁺ with standard KSCN → end point = permanent blood-red color
7Calculate: Cl⁻ (mEq) = mEq AgNO₃ added - mEq KSCN used
Normal urine chloride: 110-250 mEq/24 hours.
The key reason HNO₃ is added is to keep the solution acidic - ferric ion (Fe³⁺) hydrolyses in neutral/alkaline medium and the indicator would not work. AgNO₃ must always be added before HNO₃ to avoid loss of chloride as HCl gas.
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