Equipment Maintenance, Calibration and Verification Procedure

Procedure number	08
ISO/IEC 17025 reference	Clause 6.4
Revision	00
Effective date	[Enter date]
Approved by	[Quality Manager / Laboratory Director]

1. Purpose

To ensure that all equipment contributing to the validity of laboratory results is suitable for its intended use, properly maintained, calibrated or verified at defined intervals, and that its status is known and documented at all times.

2. Scope

This procedure applies to all equipment that can influence the result of a measurement, directly or indirectly, including:

• Analytical instruments — ICP-OES, HPLC-UV, Karl Fischer coulometric titrator, laser diffraction particle size analyzer, BET surface area analyzer, X-ray diffractometer (XRD)
• Measurement standards and reference equipment — Certified reference weights, calibrated thermometers, calibrated volumetric glassware
• Sample preparation equipment — Analytical balances, microbalances, microwave digestion systems, hotplates, muffle furnaces, ultrasonic baths
• Volumetric delivery devices — Calibrated pipettes (fixed and variable volume), burettes
• Environmental monitoring equipment — Temperature and humidity data loggers, thermometers in storage areas
• Supporting equipment — Fume hoods (airflow verification), centrifuges, ovens, desiccators, water purification systems

This procedure does not apply to general-purpose equipment that has no influence on measurement results (e.g., office printers, non-analytical refrigerators).

3. References

• ISO/IEC 17025:2017, Clause 6.4 — Equipment
• ISO/IEC 17025:2017, Clause 6.5 — Metrological traceability
• ISO/IEC 17025:2017, Clause 7.7 — Ensuring the validity of results
• ILAC P10 — ILAC Policy on Metrological Traceability of Measurement Results
• Procedure 00 — Document and Record Control
• Procedure 05 — Addressing Risks and Opportunities
• Procedure 06 — Externally Provided Products and Services
• Procedure 07 — Facilities and Environmental Conditions
• Procedure 14 — Complaints, Nonconformity and Corrective Action

4. Definitions

Term	Definition
Equipment	Any measuring instrument, software, measurement standard, reference material, auxiliary apparatus, reagent, or combination thereof necessary to perform laboratory activities.
Calibration	An operation that, under specified conditions, establishes a relation between the quantity values provided by measurement standards and the corresponding indications of the measuring system, including the associated measurement uncertainty. Calibration does not include adjustment.
Verification	Provision of objective evidence that a given item fulfils specified requirements. For equipment, this means confirming that the instrument meets its performance specification or the laboratory's acceptance criteria.
Intermediate check	A check performed between scheduled calibrations to maintain confidence in the calibration status of the equipment. Does not replace calibration.
Adjustment	A set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given values of a quantity to be measured. Adjustment may follow calibration but is a separate operation.
Metrological traceability	The property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.
Out of tolerance	A condition where the equipment's performance, as determined by calibration or verification, exceeds the acceptable limits defined by the laboratory.
Equipment register	A maintained list of all equipment subject to this procedure, including unique identification, calibration status, and location.
Preventive maintenance	Planned activities performed at defined intervals to maintain equipment in proper working condition and reduce the likelihood of failure.

5. Responsibilities

Role	Responsibility
Laboratory Director	Approve capital equipment purchases. Ensure adequate budget for calibration and maintenance programs. Authorize equipment disposal.
Quality Manager	Maintain the Equipment Register (08-App-01). Track calibration and verification schedules. Ensure overdue items are escalated. Coordinate external calibration services.
Technical Manager	Define calibration intervals, acceptance criteria, and intermediate check procedures for each item. Evaluate the impact of out-of-tolerance findings. Approve equipment for return to service after repair or calibration.
Analysts	Perform intermediate checks and routine maintenance as defined in SOPs. Record equipment use. Report faults or suspected malfunctions immediately. Do not use equipment that is overdue for calibration or labeled out of service.
External calibration providers	Perform calibrations within their accredited scope and provide certificates meeting the requirements of Procedure 06.

6. Procedure — Equipment Identification and Registration

6.1 Unique identification

Every item of equipment subject to this procedure is assigned a unique identification code. The code follows the format:

[Category]-[Sequential number]

Categories:

Code	Category	Examples
AI	Analytical instrument	ICP-OES, HPLC, XRD, BET, Karl Fischer, laser diffraction
BA	Balance	Analytical balances, microbalances
VD	Volumetric delivery device	Pipettes, burettes
SP	Sample preparation equipment	Microwave digestion, hotplates, muffle furnaces
RS	Reference standard	Certified reference weights, calibrated thermometers
EM	Environmental monitoring	Temperature loggers, hygrometers
SE	Supporting equipment	Fume hoods, ovens, centrifuges, water purifiers

Example: AI-001 (ICP-OES spectrometer), BA-003 (analytical balance in balance room 2), VD-012 (100 µL variable pipette).

The identification code is physically affixed to the equipment by label, engraving, or tag. Where labeling is impractical (e.g., small items, glassware sets), the identification is linked to the storage location.

6.2 Equipment register

All equipment is recorded in the Equipment Register (Appendix 08-App-01). The register includes:

• Unique identification code
• Equipment description, manufacturer, model, serial number
• Date of acquisition, date placed into service
• Current location
• Calibration status (calibrated / verified / due / overdue / out of service)
• Calibration interval and next due date
• Condition (in service / out of service / decommissioned)

The register is maintained by the Quality Manager and reviewed at least annually.

6.3 New equipment — commissioning

Before new equipment is placed into service:

1. Receipt inspection — Verify the equipment against the purchase order, check for damage, confirm all components and documentation are present.
2. Installation — Install according to manufacturer instructions. Verify utilities (power, gas, water, ventilation) meet requirements per Procedure 07.
3. Initial calibration or verification — Perform calibration or verification before use. For analytical instruments, this typically includes the manufacturer's installation qualification (IQ) and operational qualification (OQ) where applicable.
4. Performance confirmation — Demonstrate that the equipment meets the laboratory's performance requirements using reference materials or known samples. This may overlap with method validation if the equipment is for a new method.
5. Registration — Add the equipment to the Equipment Register and the Calibration and Verification Schedule (Appendix 08-App-02).
6. Training — Confirm that all analysts who will use the equipment have been trained per Procedure 04.
7. Authorization — The Technical Manager authorizes the equipment for routine use by signing the commissioning record.

6.4 Equipment out of direct control

When equipment is used outside the laboratory's permanent facilities (e.g., portable instruments for field work) or has been outside the laboratory's direct control (e.g., returned from external repair), the laboratory verifies its calibration status and functional performance before returning it to service.

7. Procedure — Calibration

7.1 Calibration strategy

The Technical Manager determines, for each item of equipment, whether calibration is:

• Required — The equipment measures a quantity that directly enters the measurement result and requires metrological traceability. Examples: analytical balances (mass), ICP-OES (elemental concentration via calibration curves), pipettes (volume).
• Not required but verification is needed — The equipment contributes to result quality but is not calibrated in the metrological sense. Instead, its performance is verified against defined criteria. Examples: muffle furnaces (temperature verified with a calibrated thermometer), centrifuges (speed verified), fume hoods (face velocity verified).

This determination is documented in the Calibration and Verification Schedule (Appendix 08-App-02).

7.2 Metrological traceability

All calibrations must be traceable to the International System of Units (SI) through an unbroken chain of calibrations, each with stated measurement uncertainty.

For the battery materials laboratory, traceability chains include:

Measurand	Traceability chain
Mass	Certified reference weights → national mass standards (via accredited calibration laboratory) → BIPM
Elemental concentration (ICP-OES)	Certified reference materials (CRMs) → ISO 17034 producer → national metrology institute → SI
Volume (pipettes, glassware)	Gravimetric verification using calibrated balance and calibrated thermometer → SI (mass, temperature)
Temperature	Calibrated reference thermometers → accredited calibration laboratory → national standards → ITS-90
Moisture (Karl Fischer)	Certified water standards → ISO 17034 producer → SI
Particle size (laser diffraction)	Certified size standard reference materials → national metrology institute
Specific surface area (BET)	Certified BET reference materials (e.g., alumina, carbon black) → ISO 17034 producer
Wavelength / 2θ (XRD)	Certified standard reference material (e.g., NIST SRM 660 LaB₆) → national metrology institute

Where SI traceability is not technically possible, the laboratory uses other recognized references (e.g., certified reference materials, agreed method-defined standards) and documents the traceability basis.

7.3 External calibration

Equipment calibrated by external service providers must meet the requirements of Procedure 06 — Externally Provided Products and Services. The external provider must:

• Be accredited to ISO/IEC 17025 for the relevant calibration scope
• Issue calibration certificates that include: equipment identification, calibration date, environmental conditions, reference standards used with traceability statements, measurement results with associated uncertainty, and a statement of conformity to specification (if requested)

Upon receipt of an external calibration certificate, the Technical Manager:

1. Reviews the certificate for completeness
2. Verifies that results are within the laboratory's acceptance criteria
3. Updates the Equipment Register and Calibration Schedule
4. Affixes or updates the calibration status label on the equipment

7.4 Applying correction factors

When calibration results include correction factors or reference values (e.g., balance correction at a specific load point, thermometer offset), the laboratory shall:

• Record the correction factor or reference value and its associated uncertainty
• Implement the correction in calculations or data systems where it materially affects results
• Update correction factors each time the equipment is recalibrated
• Verify that corrections have been correctly applied (e.g., by checking a calculation with and without the correction)

Where a correction factor is small relative to the method's required uncertainty and does not materially affect results, the Technical Manager may document the decision not to apply it, with justification.

7.5 Internal calibration

For equipment calibrated in-house, the laboratory documents the calibration procedure in the relevant SOP. Internal calibrations must:

• Use reference standards that are themselves calibrated with valid traceability
• Follow a documented procedure that specifies the method, reference standards, environmental conditions, number of measurements, and acceptance criteria
• Include measurement uncertainty estimation
• Be performed by trained and authorized personnel
• Be recorded in full, with raw data retained

Common internal calibrations in the battery materials laboratory:

Equipment	Internal calibration method
Analytical balances	Verification with certified reference weights at multiple points across the range. External calibration by accredited provider annually; internal verification monthly or as defined.
Pipettes	Gravimetric method — dispensed water weighed on calibrated balance, corrected for temperature and air buoyancy. Performed annually or per manufacturer recommendation.
ICP-OES	Daily calibration using multi-element calibration standards prepared from certified stock solutions. Linearity and sensitivity verified.
HPLC-UV	Wavelength accuracy verified with reference standard solutions. Flow rate verified gravimetrically.
Karl Fischer titrator	Calibrated using certified water standard before each batch.
Laser diffraction	Verified using certified particle size reference material (e.g., glass beads, latex spheres).
BET analyzer	Verified using certified BET surface area reference material (e.g., NIST SRM or equivalent).
XRD	2θ alignment verified using certified peak position standard (e.g., NIST SRM 660c LaB₆).

7.6 Calibration intervals

Calibration intervals are set by the Technical Manager based on:

• Equipment manufacturer recommendations
• Stability of the equipment demonstrated by historical calibration data
• Frequency and severity of use
• Environmental conditions
• Required measurement accuracy
• Accreditation body requirements or guidelines

Initial intervals for new equipment are based on manufacturer recommendations. Intervals may be adjusted based on accumulated performance data:

• Extended — If consecutive calibrations show the equipment is well within tolerance, the interval may be lengthened. The decision and justification are documented.
• Shortened — If a calibration reveals drift approaching tolerance limits, or if the equipment is subjected to heavy use or harsh conditions, the interval is shortened.

Typical intervals for the battery materials laboratory:

Equipment	Calibration type	Typical interval
Analytical balances	External accredited calibration	Annually
Analytical balances	Internal verification (reference weights)	Monthly
Pipettes	Gravimetric calibration	Annually
Reference weights	External accredited calibration	Every 5 years
Temperature data loggers	External accredited calibration	Annually
Reference thermometers	External accredited calibration	Every 2 years
ICP-OES	Daily calibration (standard curves)	Each analytical run
ICP-OES	Performance verification (QC check standards)	Each analytical run
HPLC	System suitability check	Each analytical run
Karl Fischer	Certified water standard check	Each batch
Laser diffraction	Reference material check	Monthly or per SOP
BET	Reference material check	Quarterly or per SOP
XRD	Alignment standard check	Monthly or per SOP

:::tip Adapt these intervals The intervals above are starting points. Your actual intervals must be justified by your equipment's demonstrated stability, your measurement requirements, and any accreditation body guidance. Document the rationale for each interval. :::

7.7 Acceptance criteria

For each calibration or verification, the Technical Manager defines acceptance criteria — the maximum permissible deviation from the reference value or specification. Criteria are based on:

• The measurement uncertainty required by the test method
• Equipment manufacturer specifications
• Regulatory or accreditation requirements
• A general principle: calibration uncertainty should be small relative to the method's required uncertainty (commonly, calibration uncertainty contributes no more than one-third of the total method uncertainty)

Examples:

Equipment	Parameter	Typical acceptance criterion
Analytical balance (0.1 mg)	Accuracy at test loads	≤ ±0.2 mg at each test point
Pipette (100 µL)	Accuracy	≤ ±1.0% of nominal volume
Pipette (100 µL)	Precision (CV)	≤ 0.5%
Reference thermometer	Deviation from standard	≤ ±0.1 °C
ICP-OES calibration	Correlation coefficient (r²)	≥ 0.9995
ICP-OES QC check standard	Recovery	Within ±5% of certified value
Karl Fischer water standard	Recovery	Within ±3% of certified value
XRD peak position standard	2θ deviation	≤ ±0.02° 2θ

8. Procedure — Intermediate Checks

8.1 Purpose of intermediate checks

Intermediate checks are performed between scheduled calibrations to maintain confidence that the equipment continues to perform within its specifications. They are not a substitute for calibration — they are a monitoring tool that provides early warning of drift or malfunction.

8.2 Intermediate check methods

The Technical Manager defines the intermediate check method, frequency, and acceptance criteria for each item of equipment that requires them. Common approaches:

Equipment	Intermediate check method	Frequency
Analytical balances	Check with one or two reference weights (not the full calibration set)	Daily before use or weekly
Pipettes	Gravimetric check at one nominal volume	Quarterly
ICP-OES	Independent QC check standard (different lot from calibration standards)	Every analytical run
HPLC	System suitability test (resolution, tailing factor, retention time)	Every analytical run
Karl Fischer	Certified water standard recovery	Every batch
Temperature loggers	Comparison against reference thermometer	Quarterly
Laser diffraction	Certified size standard	Monthly
XRD	Peak position standard scan	Monthly

8.3 Recording and acting on intermediate check results

Intermediate check results are recorded in the equipment logbook or electronic record. If an intermediate check fails (result outside acceptance criteria):

1. The equipment is taken out of service immediately
2. The Technical Manager is notified
3. The cause is investigated — the failure may indicate drift, malfunction, or a problem with the check standard itself
4. A full calibration or verification is performed before the equipment is returned to service
5. If drift is confirmed, the impact on results produced since the last satisfactory check is assessed (see section 11)

9. Procedure — Maintenance

9.1 Preventive maintenance

Each item of equipment has a preventive maintenance schedule defined by the Technical Manager, based on manufacturer recommendations and the laboratory's experience. Maintenance activities are recorded in the Equipment Maintenance and Fault Log (Appendix 08-App-03).

Typical preventive maintenance for the battery materials laboratory:

Equipment	Maintenance activity	Frequency
ICP-OES	Clean torch assembly, inspect nebulizer, check peristaltic pump tubing, clean spray chamber, inspect sample introduction system	Weekly / as needed
ICP-OES	Full preventive maintenance by manufacturer service engineer	Annually
HPLC	Replace pump seals, inspect check valves, flush system, replace in-line filters, lamp replacement (UV detector)	Per manufacturer schedule or usage hours
Karl Fischer	Replace desiccant, clean titration cell, replace diaphragm, check electrode	Per manufacturer schedule
Laser diffraction	Clean optical windows, verify alignment, check dispersion unit	Per manufacturer schedule
BET analyzer	Leak check, replace seals, verify dewar fill system, clean manifold	Per manufacturer schedule
XRD	Check X-ray tube hours, inspect cooling system, clean optics, verify goniometer alignment	Per manufacturer schedule
Balances	Clean weighing pan, check level, inspect draft shield	Before each use
Pipettes	Inspect tips, check seals, lubricate piston	At each calibration
Microwave digestion	Inspect vessels for damage, check seals, clean temperature probes	After each use / monthly
Water purification system	Replace filters and cartridges, sanitize, check resistivity	Per manufacturer schedule

9.2 Corrective maintenance (fault response)

When equipment malfunctions or is suspected to be faulty:

1. Stop using the equipment immediately. Remove it from service.
2. Label the equipment with an "OUT OF SERVICE" tag indicating the date and reason.
3. Report the fault to the Technical Manager and record it in the Equipment Maintenance and Fault Log (Appendix 08-App-03).
4. Assess impact — The Technical Manager determines whether results produced since the last satisfactory performance check may have been affected (see section 11).
5. Repair — Arrange repair by qualified personnel (in-house or external service provider per Procedure 06).
6. Post-repair verification — After repair, perform a calibration or verification to confirm the equipment meets specifications before returning it to service.
7. Authorization — The Technical Manager authorizes the return to service, documented in the maintenance log.

9.3 Software and firmware

When instrument software or firmware is updated:

1. The update is evaluated for potential impact on measurement results
2. A backup of the current configuration is made where possible
3. After the update, the instrument's performance is verified using reference materials or check standards
4. The update is recorded in the equipment record, including the previous and new version numbers

10. Procedure — Equipment Labeling and Status

10.1 Calibration status labels

Each item of calibrated or verified equipment bears a label or tag showing:

• Equipment ID
• Date of last calibration or verification
• Next calibration or verification due date
• Performed by (initials or name)
• Status: IN SERVICE / OUT OF SERVICE / FOR REFERENCE ONLY

Where a physical label is impractical, the calibration status is maintained in the Equipment Register and is accessible to all analysts.

10.2 Status categories

Label	Meaning
IN SERVICE (green)	Equipment is calibrated, verified, maintained, and authorized for use.
OUT OF SERVICE (red)	Equipment is not to be used — awaiting calibration, repair, or investigation.
FOR REFERENCE ONLY (yellow)	Equipment may be used for indication purposes but not for measurements that contribute to reported results.
DECOMMISSIONED	Equipment has been permanently withdrawn from service.

10.3 Safeguarding against unauthorized adjustments

The laboratory takes practical measures to prevent adjustments to equipment that would invalidate results:

• Password or access protection — Instrument software calibration parameters and method settings are protected by user-level access controls where the instrument supports this (e.g., ICP-OES method parameters, HPLC acquisition settings, XRD goniometer alignment). Only authorized personnel (Technical Manager or designated analysts) may modify calibration settings.
• Physical seals — Where applicable, calibration adjustment points are sealed or protected (e.g., balance internal adjustment mechanism, reference thermometer). Broken seals are reported to the Technical Manager immediately.
• Configuration records — Key instrument settings and calibration parameters are documented. Any change to these settings is recorded, including the previous value, new value, reason, and the person who made the change.
• Audit trail — For instruments with electronic data systems, audit trail functionality is enabled where available, recording all changes to methods, calibrations, and settings with timestamps and user identification.

10.4 Overdue calibration

Equipment that has passed its calibration due date without being recalibrated is immediately placed OUT OF SERVICE. It must not be used until calibration or verification is completed and the Technical Manager authorizes its return to service.

The Quality Manager monitors calibration due dates and issues reminders at least 30 days before the due date.

11. Procedure — Handling Out-of-Tolerance and Nonconforming Equipment

11.1 Identifying the problem

An out-of-tolerance condition is identified when:

• Calibration results exceed the defined acceptance criteria
• An intermediate check fails
• An analyst observes abnormal instrument behavior
• QC data (check standards, blanks, duplicates) shows unacceptable deviation
• External audit or proficiency testing reveals equipment-related problems

11.2 Impact assessment

When equipment is found to be out of tolerance or malfunctioning, the Technical Manager conducts a retrospective impact assessment:

1. Determine the affected period — From the current finding back to the last satisfactory calibration, verification, or intermediate check.
2. Identify affected results — Review laboratory records to identify all samples and reports produced using the equipment during the affected period.
3. Assess the magnitude — Determine whether the out-of-tolerance condition could have caused results to exceed the method's stated uncertainty or the customer's required accuracy. Consider:
   • The magnitude and direction of the drift or error
   • The sensitivity of the affected methods to the parameter in question
   • Whether QC data from the affected period showed any anomalies
   • Whether the error would have been detectable by other quality controls in place
4. Decision — Based on the assessment:
   • No impact: The deviation is within the method's uncertainty and does not affect reported results. Document the assessment and justification.
   • Potential impact: Results may be affected. Re-analyze affected samples where possible. Where re-analysis is not possible (sample consumed, time-critical), assess whether the deviation materially changes the reported result.
   • Confirmed impact on reported results: Notify affected customers. Issue amended reports. Record as a nonconformity per Procedure 14.

11.3 Corrective action

Following an out-of-tolerance finding:

1. The equipment is recalibrated, repaired, or adjusted as appropriate
2. Post-correction verification confirms the equipment is within tolerance
3. The root cause is investigated (e.g., environmental change, component wear, usage beyond capability)
4. If a systemic cause is identified, corrective action is initiated per Procedure 14 — this may include shortening calibration intervals, increasing intermediate checks, or replacing the equipment
5. All actions are documented in the Equipment Maintenance and Fault Log

12. Procedure — Equipment Records

12.1 Records to be maintained

For each item of equipment, the laboratory maintains the following records:

Record	Content	Retention
Equipment Register (08-App-01)	Identification, description, status, location	Life of equipment + 5 years
Calibration certificates (external)	Issued by calibration provider	Calibration interval + 5 years
Internal calibration records	Raw data, calculations, results, uncertainty, pass/fail	Calibration interval + 5 years
Intermediate check records	Check results, pass/fail	5 years
Calibration and Verification Schedule (08-App-02)	Intervals, due dates, responsibilities	Current + previous versions
Maintenance and Fault Log (08-App-03)	Maintenance activities, faults, repairs, return-to-service	Life of equipment + 5 years
Manufacturer manuals and documentation	Operating instructions, specifications, service manuals	Life of equipment
Out-of-tolerance impact assessments	Assessment, decision, corrective action	5 years
Equipment commissioning records	Receipt inspection, IQ/OQ, initial calibration, authorization	Life of equipment

Records are managed according to Procedure 00 — Document and Record Control.

12.2 Equipment logbooks

Each major analytical instrument (ICP-OES, HPLC, XRD, BET, Karl Fischer, laser diffraction) has an equipment logbook (physical or electronic) that records:

• Date and time of use
• Analyst name
• Samples or batches analyzed
• Calibration data for the session (e.g., calibration curve parameters, QC check results)
• Any observations or anomalies
• Maintenance performed

13. Procedure — Disposal and Decommissioning

When equipment is permanently removed from service:

1. The Technical Manager confirms the equipment is no longer needed
2. The Laboratory Director authorizes disposal
3. The equipment is removed from the active Equipment Register (marked as decommissioned with the date)
4. Calibration and maintenance records are retained per section 12.1
5. If the equipment contained hazardous materials (e.g., X-ray tubes, mercury thermometers), disposal follows the laboratory's waste management and safety procedures
6. Data stored on the equipment is archived or transferred before disposal

14. Related documents

Document	Reference
Appendix 1 — Equipment Register	08-App-01
Appendix 2 — Calibration and Verification Schedule	08-App-02
Appendix 3 — Equipment Maintenance and Fault Log	08-App-03
Procedure 00 — Document and Record Control	Procedure 00
Procedure 04 — Competence, Training and Awareness	Procedure 04
Procedure 05 — Addressing Risks and Opportunities	Procedure 05
Procedure 06 — Externally Provided Products and Services	Procedure 06
Procedure 07 — Facilities and Environmental Conditions	Procedure 07
Procedure 14 — Complaints, Nonconformity and Corrective Action	Procedure 14

15. Revision history

Revision	Date	Description	Approved by
00	[Date]	Initial issue	[Name]

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Why this section exists

Section 08 addresses the physical foundation that every measurement rests on: the instruments and standards the laboratory uses to produce numbers.

A measurement result is only as reliable as the chain of comparisons that connects it to a recognized reference. When a laboratory reports that a cathode material contains 58.2% nickel, that number derives from a calibration curve, which derives from calibration standards, which derive from certified reference materials, which derive from a national metrology institute's primary standards, which derive from the SI definition of the mole. If any link in that chain is broken — an uncalibrated balance, an expired reference material, a drifting detector — the number the customer receives may be precise, reproducible, and wrong.

Calibration is not adjustment

One of the most common misunderstandings in laboratory practice is confusing calibration with adjustment. Calibration determines the relationship between what an instrument reads and what the true value is. Adjustment changes the instrument so that it reads closer to the true value. These are separate operations, and the distinction matters.

When a balance is calibrated, the laboratory places certified reference weights on the pan and records what the balance displays. If the balance reads 99.9998 g for a 100.0000 g weight, the balance has been calibrated — the relationship between the indication (99.9998 g) and the reference value (100.0000 g) is now known. The laboratory can apply a correction, or it can determine that the deviation is negligible for its purposes.

If the laboratory then adjusts the balance so that it reads 100.0000 g, it has changed the instrument. The pre-adjustment calibration data is now historical. A new calibration after adjustment establishes the new relationship. Both the "as found" (pre-adjustment) and "as left" (post-adjustment) data are important — the "as found" data tells the laboratory what the balance was actually doing while it was in use, and the "as left" data confirms the adjustment was successful.

The intermediate check as early warning

The calibration interval defines how long the laboratory trusts an instrument between formal calibrations. A balance calibrated every 12 months is assumed to be in tolerance for those 12 months. But what if it drifts out of tolerance in month 3? Without intermediate checks, the laboratory discovers this at the next annual calibration — and then faces a 9-month window of potentially affected results.

Intermediate checks reduce this risk. A monthly weight check on the balance means the maximum affected window is one month, not twelve. The check does not replace calibration — it does not establish full traceability or determine measurement uncertainty. But it confirms, at a defined confidence level, that the instrument has not drifted beyond acceptable limits.

The design of intermediate checks is important. An intermediate check should use a reference that is independent of the equipment's own calibration. For ICP-OES, this means running a QC check standard from a different supplier or lot than the calibration standards. If both the calibration standards and the QC check come from the same stock solution, the check is circular — it would not detect a preparation error in that stock solution.

Equipment records tell a story

An equipment maintenance and calibration file is not just a compliance artifact. Over time, it becomes the history of the instrument — showing patterns of drift, recurring faults, the effect of environmental changes, and how the instrument's performance evolves as it ages. This history is the basis for intelligent decisions about calibration intervals, replacement timing, and root cause analysis when things go wrong.

A laboratory that keeps meticulous calibration records can demonstrate, with data, that a balance is stable enough to extend its calibration interval from 12 to 18 months. A laboratory with sketchy records cannot make that argument — and an assessor will not accept it.

The out-of-tolerance cascade

The most consequential event in equipment management is discovering that an instrument was out of tolerance. The instrument itself is easily fixed — recalibrate, adjust, or repair. The difficult part is what happened before the problem was found.

Every result produced by that instrument since the last satisfactory calibration or intermediate check is now in question. The laboratory must identify those results, assess whether the out-of-tolerance condition actually affected them, and decide whether to inform customers. This is the retrospective impact assessment — and it is often the most time-consuming and uncomfortable activity in the entire quality management system.

The practical lesson is that the investment in intermediate checks, daily QC checks, and prompt investigation of anomalies is not bureaucratic overhead. It is insurance against the out-of-tolerance cascade. The sooner drift is detected, the smaller the window of affected results, the fewer customers need to be notified, and the less damage is done to the laboratory's credibility.

The ICP-OES calibration paradox

ICP-OES presents an interesting case because it is calibrated with every analytical run. The analyst prepares calibration standards, runs them, builds a calibration curve, and then measures samples against that curve. In one sense, the instrument is calibrated every day — more frequently than any other instrument in the laboratory.

But the calibration curve is only as good as the standards used to build it. If the stock solution used to prepare calibration standards has degraded, or was prepared incorrectly, or has been contaminated, the calibration curve will be biased — and every sample measured against it will carry that bias. The instrument passes its daily calibration because the calibration is self-referential.

This is why the independent QC check standard is critical. It breaks the circularity. A check standard prepared from a different stock solution, ideally from a different supplier, provides an independent reference point. If the calibration curve says the QC check standard should read 10.0 mg/L and it actually reads 10.3 mg/L, something is wrong — either with the calibration standards, the QC standard, or the instrument. The investigation begins, but at least the problem has been detected before customer samples are reported.

What "fit for purpose" actually means

ISO/IEC 17025 does not require the most accurate equipment available. It requires equipment that is adequate for the intended measurements. A laboratory measuring nickel at 50–60% in cathode materials does not need a balance readable to 0.001 mg — a balance readable to 0.1 mg is more than sufficient. But a laboratory performing trace impurity analysis at the µg/g level in the same materials may need exactly that precision for weighing small samples.

"Fit for purpose" means the equipment's measurement capability — including its calibration uncertainty — is compatible with the measurement uncertainty the laboratory claims for its results. If the laboratory's reported uncertainty for nickel by ICP-OES is ±0.5%, then every instrument in the measurement chain (balance, volumetric ware, ICP-OES detector) must contribute an uncertainty that is small enough, in combination, to support that claim. Section 08 ensures the equipment is calibrated well enough to make the laboratory's uncertainty budget honest.

Common nonconformities

Clause 6.4 is one of the most heavily audited sections of ISO 17025. The evidence is concrete — calibration certificates, maintenance logs, equipment registers — and auditors can verify compliance by simply opening a file and checking a date. The examples below cover the findings that appear most frequently in assessment reports.

Major Equipment used past its calibration due date

"Analytical balance BA-002 had a calibration due date of 15 January 2025. At the time of the assessment (14 March 2025), the balance was in routine use for weighing cathode material samples. No recalibration had been performed, and the balance was not labeled as overdue or out of service."

This is the single most common equipment finding in ISO 17025 assessments. Section 10.4 of this procedure is unambiguous: equipment past its calibration due date is out of service. The finding is major because every result produced on that balance since January is now in question. The retrospective impact assessment (Section 11.2) must cover the full two-month window, and any affected reports may need to be amended.

Major No retrospective impact assessment after out-of-tolerance finding

"The annual calibration of pipette VD-005 (100 µL) revealed a systematic bias of +2.8%, exceeding the ±1.0% acceptance criterion. The pipette was recalibrated and returned to service. However, no assessment of the impact on results produced with that pipette during the preceding 12 months was documented."

Fixing the equipment is only half the response. The other half — and the more important half — is asking what happened to the results produced while the equipment was out of tolerance. A +2.8% volume bias means every sample prepared with that pipette received 2.8% more reagent or diluent than intended. Depending on the method, this could shift results by a measurable amount. Section 11.2 requires that the laboratory trace back to the last satisfactory calibration, identify affected results, and assess whether any reported values need to be corrected.

Minor Equipment register incomplete or not current

"The Equipment Register listed 34 items. A walkthrough of the laboratory identified three additional items in routine use — two temperature data loggers and a set of volumetric flasks — that were not in the register and had no calibration records."

If equipment is not in the register, it is invisible to the calibration system. It will not appear on the calibration schedule, it will not receive intermediate checks, and no one will notice when its calibration lapses. This finding is minor when the missing items are supporting equipment, but it can escalate to major if the unregistered items directly affect measurement results — as volumetric flasks used in standard preparation would.

Minor Intermediate checks not performed or not recorded

"The procedure specified monthly intermediate checks on analytical balances using certified reference weights. The check log for balance BA-001 showed entries for January, February, and March, but no entries from April through September — a six-month gap. The analyst confirmed the checks had not been performed."

Intermediate checks exist to narrow the window of risk between calibrations. A six-month gap means that if the balance drifted out of tolerance in April, the laboratory would not know until the next annual calibration — and would then face a retrospective assessment spanning many months of results. The finding is minor because the annual calibration was current, but it reveals that the early warning system was not functioning.

Major No metrological traceability for calibration standards

"ICP-OES calibration standards were prepared from a multi-element stock solution purchased from a chemical supplier. The stock solution had a certificate of analysis listing concentration values, but no statement of metrological traceability to SI units or to a national metrology institute. The supplier was not accredited to ISO 17034."

Traceability is the backbone of Clause 6.5 and it feeds directly into equipment calibration. If the calibration standards used for ICP-OES are not traceable, then the calibration curves built from them are not traceable, and consequently every result derived from those curves has no metrological foundation. The laboratory may be producing precise and reproducible numbers, but it cannot demonstrate that those numbers are accurate in any absolute sense. This is a fundamental metrological gap, not an administrative one.

Minor Calibration status labels missing or outdated

"Of 15 items of equipment inspected, four did not bear calibration status labels: two pipettes, one reference thermometer, and one temperature data logger. A fifth item (analytical balance BA-003) had a label showing a next-due date that had passed three months earlier, though the calibration had in fact been performed on time — the label had not been updated."

Labels are the first-line control that allows any analyst to confirm, at a glance, whether a piece of equipment is safe to use. Missing or outdated labels create a risk that someone will use equipment that is out of service, or conversely, will hesitate to use equipment that is actually current. The finding is minor when the underlying calibrations are in order, but it signals a housekeeping gap in the equipment management system.

Major No documented acceptance criteria for calibration results

"Calibration certificates for three analytical balances and two reference thermometers were on file. When asked what the laboratory's acceptance criteria were for these calibrations — i.e., the maximum permissible deviation — the Technical Manager stated the criteria were 'whatever the manufacturer specifies' but could not point to documented criteria linked to the laboratory's measurement requirements."

Acceptance criteria are what turn a calibration from a measurement exercise into a decision tool. Without them, the laboratory cannot determine whether an instrument is in tolerance or out of tolerance — and therefore cannot trigger the impact assessment process in Section 11. The criteria must be documented, traceable to the laboratory's measurement uncertainty requirements, and applied consistently when calibration certificates are reviewed. "Whatever the manufacturer says" is not a criterion — it is an abdication of the laboratory's responsibility to define its own fitness-for-purpose requirements.

How to use these examples

Equipment nonconformities follow a predictable pattern: the laboratory has equipment, uses it, and may even calibrate it — but somewhere in the chain of register → calibrate → check → label → assess impact → act a link is missing. When reviewing your own equipment system, pick any instrument from the register and trace its full lifecycle: is it registered? Is its calibration current and traceable? Are intermediate checks being done? Is the status label correct? Has every out-of-tolerance finding triggered an impact assessment? If you can answer yes for every item in the register, your Section 08 is sound.