DAILY BALANCE VERIFICATION [PICTORIAL]

Daily balance verification in pharma is the routine, documented checking of analytical balances each day they’re used to ensure they are accurate and fit for use in GMP testing. It’s a pre-use fitness check, not a full calibration.

Here’s a crisp, SOP-style explanation you can directly adapt.

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1. Purpose

• To confirm that each analytical balance used for GMP/testing is:
  • Functioning correctly
  • Within predefined accuracy/precision limits
  • Safe to use for weighing of reagents, standards, and samples

If daily verification fails → do not use the balance for any GMP work until investigated and found acceptable.

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2. What Needs to Be Defined in SOP

Your “Daily Balance Verification” SOP should clearly define:

1. Scope
   • All analytical balances used in:
     • QC lab
     • Production (dispensing, weighing rooms)
     • R&D (if data used for CGMP decisions)
2. Frequency
   • At the beginning of each day of use
   • Additionally:
     • After relocation
     • After power failure
     • If the balance shows abnormal behavior (drift, error messages, or suspected damage)
3. Responsibility
   • Trained analysts / production operators
   • Review by QA/QC supervisor (for trend and OOS actions)

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3. Pre-Checks Before Verification

Before starting daily checks:

• Ensure balance is level (spirit bubble centered).
• Draft shield doors closed (if applicable).
• Balance is clean (no spills or powder).
• Warm-up time completed (as per manufacturer).
• No strong air draft, vibration, or direct sunlight.

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4. Standard Weights and Their Control

Use certified reference weights with known values and tolerances:

• Typically Class E2 / F1 OIML or equivalent, depending on balance readability.
• Maintain:
  • Weight ID (e.g., W-10g-01)
  • Nominal value (e.g., 10 g)
  • Certificate number, traceability to national/international standards
  • Calibration due date

Weights must be:

• Stored in clean, closed boxes.
• Handled with tweezers or gloves to avoid contamination.
• Kept near the balance (same environment) for temperature equilibrium.

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5. Typical Daily Verification Procedure

You can express this as a step-wise checklist in the SOP/poster:

1. Power On & Warm-Up
   • Switch on balance (if not 24×7).
   • Allow recommended warm-up period.
2. Zero / Tare Check
   • With empty pan, press ZERO.
   • Confirm reading is 0.0000 g (or 0.00000 g depending on resolution).
3. Internal Adjustment (If Available)
   • Run internal calibration/adjustment as per manufacturer’s instructions.
   • Document performed, if your SOP requires.
4. Place Certified Weight(s)
   Recommended approach:
   • Use at least two weights:
     • One near the lower or mid-range (e.g., 10 g)
     • One near the upper range (e.g., 100 g) of routine use
   • Record displayed value vs. nominal value.
5. Calculate Error
   • Error = |Displayed value – Nominal value|
   • Check against predefined allowable tolerance (e.g., ±0.2 mg for 10 g, etc., based on risk and balance capability).
6. Repeatability Check (Optional but Good Practice)
   • Weigh the same weight 3–5 times, removing and replacing it.
   • Calculate standard deviation (or range).
   • Compare with defined acceptance criteria (e.g., σ ≤ 0.15 mg).
7. Return to Zero
   • Remove weight and ensure balance returns to 0.0000.
   • If not, investigate and repeat as needed.
8. Documentation
   • Record in a log:
     • Date & time
     • Balance ID
     • Weight ID(s)
     • Nominal vs. observed values
     • Calculated error
     • Pass/Fail
     • Analyst initials/signature

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6. Acceptance Criteria (Example)

These must be defined in your validation/QRM, but common pattern:

• Accuracy:
  • Error for 10 g weight must be within ±0.002 g
  • Error for 100 g weight within ±0.02 g
    (Adjust for your balance readability and process criticality.)
• Repeatability:
  • Standard deviation ≤ 0.0002 g for 10 g weight over 5 measurements
  • Or %RSD within predetermined limits

You can link these to your calibration certificate and balance qualification report.

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7. What if the Balance Fails?

If any verification step fails:

1. Immediately label the balance “OUT OF SERVICE”.
2. Stop using it for any GMP weighing.
3. Notify supervisor/QA.
4. Initiate investigation:
   • Check if wrong weight used, dirty pan, drafts, etc.
   • Re-verify after corrective actions.
5. Evaluate impact on previously weighed materials:
   • Trace back to last successful verification.
   • Assess impact on results and product quality.
   • Document in deviation/OOS and decide on re-testing or re-weighing if possible.

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8. Link to Calibration and Qualification

Daily verification is complementary to:

• Periodic external calibration (e.g., 6–12 months).
• Equipment qualification (IQ/OQ/PQ).
• Preventive maintenance.

Regulators expect:

• Documented evidence that equipment is fit for intended use at the time of use.
• Daily checks + calibration + qualification together provide that assurance.