Step-by-step SOP to determine Microscopic particle size of raw materials using microscopy in QC labs, including calibration, analysis, and best practices.

🧠 Definition

Microscopic particle size determination is a quality control method used to measure and analyze the size of particles in raw materials using a calibrated microscope, ensuring uniformity, product quality, and compliance with pharmaceutical specifications.https://www.webofpharma.com/2026/02/sop-for-hplc-analysis-and-documentation.html

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📊 Micrometer Calibration

Objective Lens	1 Division Value
10X	10 µm
40X	2.5 µm
100X	1 µm

📋 Quick SOP Steps

Steps to Determine Particle Size Microscopically:

1. Prepare sample suspension using paraffin oil
2. Place drop on slide and cover with coverslip
3. Focus microscope using appropriate objective
4. Measure particles using micrometer scale
5. Analyze 200–300 particles across fields
6. Calculate particle size distribution

Introduction

Accurate particle size determination is essential in pharmaceutical quality control, as it directly affects dissolution, bioavailability, and product stability. This microscopic particle size SOP provides a reliable and standardized method to measure particle size using visual microscopy, ensuring consistency, compliance, and analytical precision.

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🧬 Semantic Content Layer

Microscopic particle size analysis involves measuring particle dimensions using a calibrated eyepiece micrometer at specific magnifications such as 10X, 40X, or 100X. The method ensures analytical accuracy, detection sensitivity, and data integrity by evaluating particle size distribution across multiple microscopic fields, supporting GMP compliance and quality assurance in pharmaceutical laboratories.

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1. Objective

To lay down the procedure for measurement of particle size of raw materials using the microscopic method.

2. Scope

Applicable for measuring and counting particle size of raw materials using visual microscopy in QC laboratories.

3. Responsibility

• Execution: Technical Assistant (QC) / Executive
• Checking: Executive / Assistant Manager (QC)

4. Accountability

• Head of Department

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⚙️ 5. SOP Procedure

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5.1 Operation (Microscopic Analysis)

Step-by-Step Procedure

1. Weigh approximately 100 mg of powder in a clean, dry test tube.
2. Add 10 ml paraffin oil and vortex for 30 seconds to form uniform suspension.
3. Place one drop on a clean slide using pipette.
4. Gently place coverslip avoiding air bubbles.
5. Mount slide on microscope.
6. Focus using 10X, 40X, or 100X objective as required.
7. Insert micrometer scale in eyepiece.

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5.2 Calibration of Microscope

Calibration Details

• Ensure eyepiece micrometer is calibrated before use
• Use stage micrometer for accuracy verification
• Apply correct division values based on objective

👉 Refer to table above for calibration values

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5.3 Measurement & Calculation

1. Select 5 different microscopic fields
2. Measure 200–300 particles
3. Record particle size using micrometer divisions
4. Convert into microns using calibration values
5. Calculate:
   • Average particle size
   • % distribution across size ranges

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5.4 Cleaning Procedure

1. Remove slide and dispose sample properly
2. Clean slide and coverslip with suitable solvent
3. Wipe microscope stage and lenses carefully
4. Switch off microscope and cover with dust cover
5. Record activity in logbook

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⚠️ Safety Precautions

• Handle microscope lenses carefully
• Avoid direct contact with optical surfaces
• Use PPE (gloves, lab coat)
• Prevent sample contamination

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❌ Common Mistakes

• Air bubbles under coverslip
• Incorrect calibration
• Measuring too few particles
• Poor focusing

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✅ Best Practices

• Analyze minimum 200 particles
• Use uniform suspension
• Perform routine calibration
• Maintain proper documentation

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📘 Abbreviations

• SOP – Standard Operating Procedure
• % – Percentage

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❓ FAQs (SEO Optimized)

1. What is microscopic particle size analysis?
   It is a method to measure particle size using a microscope and micrometer scale.
2. Why is particle size important in pharmaceuticals?
   It affects dissolution, stability, and bioavailability.
3. What is the ideal number of particles to measure?
   Typically 200–300 particles.
4. Which oil is used for suspension?
   Paraffin oil.
5. What magnification is used?
   10X, 40X, or 100X.
6. How is calibration done?
   Using stage micrometer.
7. What errors affect results?
   Air bubbles and improper calibration.
8. Is this method GMP compliant?
   Yes, when properly documented.
9. What is particle size distribution?
   Percentage of particles in different size ranges.
10. How often should calibration be done?
    As per SOP or before analysis.