Contents

4. Instrument Calibration

Effective Date: 08/06
Point of Contact: Quality Engineer for Regulatory Programs

Calibration is the process by which the response of a measurement system is related to the concentration, amount, or physical property of an analyte or parameter of interest. Calibration requirements are specific to the analytical method because of variations in instrumentation characteristics and stability. Each staff member is responsible for ensuring the results are traceable to the calibration and standards used. This section describes calibration requirements for laboratory measurement systems. See the procedures below for Externally Calibrated Equipment and User-Calibrated Equipment.

Externally Calibrated Equipment

Step 1 The user complies with the Calibration subject area.

Step 2 The user ensures that equipment, which is required in the analytical methods but that is not routinely calibrated as part of the analytical procedure (such as analytical balances), is calibrated to the manufacturer's specified tolerances or tolerances determined by the user (e.g., accuracy, precision, and sensitivity) at the frequency shown in the Minimum Calibration Requirements for Externally Calibrated Equipment exhibit.

If manufacturer's specified tolerances are not used, the user justifies the alternative tolerances and makes these tolerances available to all users.

Step 3 The user ensures that the calibrator has affixed a label that identifies the calibrating organization, the calibration date, and the date the calibration expires.

Note: Project staff cannot use externally calibrated equipment to produce analytical results unless the calibration is valid or a Calibration Extension Form has been completed as described in the Calibration subject area.

Step 4 The project or participating line organizations maintain calibration records for externally calibrated measuring and test equipment (M&TE). Records of external calibrations performed include the make, model, and unique equipment identification number of the instrument. If the line organization maintains these records, then the project files must clearly reference the records location. Additionally, the project must confirm the traceability of calibration records and acceptability of calibrations performed.

Step 5 Vendor-calibrated glassware (e.g., volumetric flasks, pipettes, burettes, syringes) is received with vendor-specified error limits, usually less than 1%. Errors associated with this type of glassware are sufficiently small; therefore, identification of individual items used is not required. Verification that glassware meets these error limit requirements is established by the vendor. No certifications are necessary.

Note: If there are additional calibration requirements, then this should be identified in the work-authorizing document.

Step 6 If thermometers are used for critical temperature measurements (e.g., sample storage, total dissolved solids), the user

• ensures they are verified against a NIST traceable thermometer before use -- (Thermometers can be purchased pre-certified, or they can be verified by the laboratory.)
• checks the thermometers annually thereafter, or before next use against a calibrated NIST traceable thermometer or thermocouple and documents the results of the check.

Laboratory verification is described below:

• The thermometer is tested at two temperatures that span the range of use for the individual thermometer.
• If the readings obtained fall within the tolerance of the thermometer, no further action is required.
• If the readings fall outside the stated tolerance, then the thermometer is either taken out of service or a temperature correction factor is determined. The temperature correction factor is the difference between the readings from the test thermometer and that of the NIST traceable one.
• The temperature correction factor is affixed to the thermometer.
• The actual temperature is then determined by adding the temperature correction factor (may be positive or negative) to the measured temperature.

The user maintains records of all thermometers used for critical temperature measurements and confirms trace ability to any performance verifications conducted. An example, Thermometer Verification, is provided.

Step 7 The user checks daily, before use, equipment that is calibrated externally or received with a fixed calibration, such as balances or mechanical pipettes, for acceptable performance. Balance performance checks shall be documented and consist of placing a weight on the balance in the expected working range and verifying if the result is within the required tolerance. Mechanical pipettes used for critical volume measurements are checked daily, before use, by measuring and documenting the weight of an aliquot of water delivered. In limited cases, where high radiation conditions exist, the laboratory uses the results of analytical and sample-related quality control as confirmation of acceptable performance.

User-Calibrated Equipment

Step 1 The user complies with the Calibration subject area.

Step 2 The user performs the calibration as required by the procedure or confirms the continued acceptability of the current calibration. The minimum requirements for calibration are given in the following exhibits:

• Calibration Requirements for Inorganic Analyses
• Calibration Requirements for Organic Analyses
• Calibration Requirements for Radiochemistry
• Minimum Calibration Requirements for Externally Calibrated Equipment (includes calibration requirements for physical chemistry, e.g., thermogravimetric analysis, differential thermal analysis/thermal gravimetry, and differential scanning calorimetry)
• Minimum Ion Abundance Requirements for Semivolatile Organic Analysis
• Minimum Ion Abundance Requirements for Volatile Organic Analysis.

Step 3 If standards are used for calibration, the project staff member

• verifies laboratory-prepared standards for concentration and/or activity, preferably by analytical crosscheck against another standard.
• at a minimum, documents and maintains the following information on standard preparations:
• • name of preparer
  • date prepared
  • unique standard identification
  • dilution performed
  • final concentration
  • expiration date or shelf-life (assigned by either the Manufacturer's specifications or recommendations, nationally accepted standards or regulations, or by the staff when no expiration date is stated, and shall be based on known chemical characteristics or decay rates).
    Note: This information is placed on the standard container or the standard container(s) must be traceable to the information.
  • maintains the standard certification records and ensures traceability of results to the standards used.

Step 4 If the calibration requirements necessary to meet project data quality needs cannot or were not met, the staff member notifies the project manager at the time of discovery and describes the problem (specifically why the criteria cannot be met), recommended action(s), and additional costs that will be incurred, if applicable. This notification must be documented. Corrective actions that do not impact cost or schedule and are within the control of the staff member do not need to be reported to the project manager.

Step 5 The project or participating line organizations maintain the user calibration records. Records of user calibrations are to be maintained in the project records to ensure that the final results reported are traceable to a valid calibration. If the line organization is used, then the project files must clearly reference where the records reside. Additionally, the project must confirm the traceability of calibration records and acceptability of calibrations performed.

References

Calibration subject area