Introduction

Tablet friability is a critical quality control parameter in the pharmaceutical industry that assesses the mechanical strength of tablets during handling, packaging, and transportation. The friability test evaluates a tablet’s ability to withstand abrasion and breakage under stress. To ensure accurate and reliable results, the friability tester must be periodically calibrated according to established guidelines. This article explores the procedures for calibrating a tablet friability tester and the key parameters that must be tested.

What is Tablet Friability Testing?

Tablet friability testing measures the tendency of tablets to break, chip, or crumble under mechanical stress. The test is conducted using a friability tester (also called a Roche friability), which subjects tablets to repetitive tumbling action within a rotating drum. The percentage of weight loss of the tablets after the test determines their friability.

Importance of Calibration in Friability Testing

Calibration of the friability tester ensures the accuracy, reliability, and reproducibility of test results. Regular calibration helps to:

• • Maintain compliance with pharmacopeial standards (USP, IP, BP, EP)

• • Ensure consistent tablet quality

• • Avoid discrepancies in test outcomes

• • Prevent batch failures due to incorrect friability values

Equipment Used in Friability Testing

• • Friability Tester (Roche Friabilator): A rotating drum with an internal baffle that exposes tablets to controlled impact.

• • Weighing Balance: A precision balance to measure tablet weight before and after testing.

• • Brush or Soft Cloth: Used for cleaning residual dust from tablets after testing.

Parameters to Be Tested in Calibration

Calibration of a friability tester involves verifying multiple parameters to ensure accurate performance. The key parameters include:

1. Rotation Speed Accuracy

• • The drum must rotate at a fixed speed, typically 25 ± 1 rpm.

• • A tachometer can be used to measure and verify the rotation speed.

• • If the speed deviates from the set value, necessary adjustments must be made.

2. Rotation Count Accuracy

• • The standard test duration involves 100 rotations (or 4 minutes at 25 rpm).

• • The rotation counter should be checked to ensure it completes exactly 100 rotations.

3. Drum Drop Height Verification

• • The drum should have a fall height of 6.3 ± 0.2 mm for each rotation.

• • The height can be measured using a calibrated scale or a height gauge.

4. Drum Integrity and Surface Condition

• • The drum should be free from cracks, scratches, or deformities that could affect tablet movement.

• • The internal baffles should be properly attached and aligned.

5. Tablet Weight Measurement Accuracy

• • The weighing balance used must be calibrated to provide accurate tablet weight measurements.

• • Weight variations should be within ± 0.1% of actual weight.

6. Tablet Loss Percentage Verification

• • The friability percentage should be calculated correctly as:

• • The acceptable limit is typically less than 1% weight loss.

Calibration Procedure for Tablet Friability Tester

Step 1: Visual Inspection

• • Check for physical damage or wear and tear on the drum and baffles.

• • Ensure the drum is securely attached and rotates freely.

Step 2: Speed Calibration

• • Use a tachometer to measure the drum rotation speed.

• • If the reading is not within 25 ± 1 rpm, adjust the settings as per the manufacturer’s instructions.

Step 3: Rotation Count Verification

• • Set the tester for 100 rotations and run a trial test.

• • Manually count or use a digital counter to confirm that the tester completes exactly 100 rotations.

• • If there is a discrepancy, recalibrate the rotation counter.

Step 4: Drop Height Measurement

• • Measure the fall height using a scale.

• • Ensure that it aligns with the required 6.3 ± 0.2 mm standard.

• • Adjust the drum position if necessary.

Step 5: Weight Calibration of Balance

• • Place standard calibration weights on the balance.

• • Ensure the balance reads accurately within the allowed tolerance.

Step 6: Test Run with Standard Tablets

• • Weigh a set of tablets before the test.

• • Run the friability test for 100 rotations.

• • Remove and weigh the tablets again after brushing off the dust.

• • Verify if the weight loss percentage is within the acceptable range.

Step 7: Documentation and Compliance

• • Record calibration results, deviations, and corrective actions.

• • Maintain calibration logs for audit and compliance purposes.

Frequency of Calibration

• • Daily Checks: Visual inspection before each use.

• • Weekly Checks: Speed and count verification.

• • Monthly Checks: Full calibration including drop height and drum integrity.

• • Annual Calibration: Complete calibration by an external agency.

Challenges in Friability Calibration

• • Environmental Factors: Variations in humidity and temperature can impact tablet weight.

• • Instrument Wear and Tear: Regular usage can lead to mechanical wear, affecting accuracy.

• • Human Error: Manual counting errors can lead to incorrect calibration readings.

Conclusion

Proper calibration of a tablet friability tester is essential for maintaining the quality and reliability of pharmaceutical products. By systematically checking and verifying key parameters such as rotation speed, count accuracy, and drop height, manufacturers can ensure compliance with regulatory standards. Regular calibration, coupled with thorough documentation, helps improve the precision of friability testing, ultimately leading to better product quality and patient safety.