Section 740. Measurement traceability and calibration

A. General requirements. All equipment used for environmental tests, including equipment for subsidiary measurements (e.g., for environmental conditions) having a significant effect on the accuracy or validity of the result of the environmental test or sampling shall be calibrated before being put into service and on a continuing basis. The laboratory shall have an established program and procedure for the calibration of its equipment. This includes balances, thermistors, thermometers and control standards. Such a program shall include a system for selecting, using, calibrating, checking, controlling and maintaining measurement standards, reference materials used as measurement standards, and measuring and test equipment used to perform environmental tests.

B. Traceability of calibration.

1. The laboratory shall ensure that the equipment used can provide the uncertainty of measurement needed.

2. The overall program of calibration or verification or both and validation of equipment shall be designed and operated so as to ensure that measurements made by the laboratory are traceable to national standards of measurement.

3. Where traceability of measurements to the International System of Units (SI) is not possible or not relevant, the same requirements for traceability to, for example, certified reference materials, agreed methods or consensus standards, are required. The laboratory shall provide satisfactory evidence of correlation of results, for example by participation in a suitable program of inter-laboratory comparisons, proficiency testing, or independent analysis.

C. Reference standards and reference materials.

1. Reference standards. The laboratory shall have a program and procedure for the calibration of its reference standards. Reference standards of measurement shall be calibrated by a body that can provide traceability as described in subsection B of this section. Such reference standards of measurement held by the laboratory (such as Class S or equivalent weights or traceable thermometers) shall be used for calibration only and for no other purpose, unless it can be demonstrated that their performance as reference standards would not be invalidated. Where commercially available, this traceability shall be to a national standard of measurement.

2. Reference materials. Reference materials shall, where commercially available, be traceable to SI units of measurement, or to certified reference materials. Where possible, traceability shall be to national or international standards of measurement, or to national or international standard reference materials. Internal reference materials shall be checked as far as is technically and economically practicable.

D. Calibration. Calibration requirements are divided into two parts: (i) requirements for analytical support equipment and (ii) requirements for instrument calibration. In addition, the requirements for instrument calibration are divided into initial instrument calibration and continuing instrument calibration verification.

1. Support equipment. These standards apply to all devices that may not be the actual test instrument, but are necessary to support laboratory operations. These include but are not limited to balances, ovens, refrigerators, freezers, incubators, water baths, temperature measuring devices (including thermometers and thermistors), thermal/pressure sample preparation devices and volumetric dispensing devices (such as Eppendorf®, or automatic dilutor or dispensing devices) if quantitative results are dependent on their accuracy, as in standard preparation and dispensing or dilution into a specified volume.

a. All support equipment shall be maintained in proper working order. The records of all repair and maintenance activities, including service calls, shall be kept.

b. All support equipment shall be calibrated or verified at least annually, using NIST traceable references when available, over the entire range of use. The results of such calibration shall be within the specifications required of the application for which this equipment is used. If not, the laboratory shall either (i) remove the equipment from service until repaired or (ii) maintain records of established correction factors to correct all measurements.

c. Raw data records shall be retained to document equipment performance.

d. On each day the equipment is used, balances, ovens, refrigerators, freezers, and water baths shall be checked in the expected use range, with NIST traceable references where available. The acceptability for use or continued use shall be according to the needs of the analysis or application for which the equipment is being used.

e. Mechanical volumetric dispensing devices including burettes (except Class A glassware) shall be checked for accuracy on at least a quarterly use basis. Glass microliter syringes are to be considered in the same manner as Class A glassware, but shall come with a certificate attesting to established accuracy or the accuracy shall be initially demonstrated and documented by the laboratory.

f. For chemical tests, the temperature, cycle time and pressure of each run of autoclaves shall be documented by the use of appropriate chemical indicators or temperature recorders and pressure gauges.

g. For biological tests that employ autoclave sterilization, the following requirements apply:

(1) The performance of each autoclave shall be initially evaluated by establishing its functional properties and performance, for example heat distribution characteristics with respect to typical uses. Autoclaves shall meet specified temperature tolerances. Pressure cookers fitted only with a pressure gauge are not recommended for sterilization of media or decontamination of wastes.

(2) Records of autoclave operations including temperature and time shall be maintained. This shall be done for every cycle. Acceptance and rejection criteria shall be established and used to evaluate the autoclave efficiency and effectiveness.

2. Instrument calibration.

a. This standard specifies the essential elements that define the procedures and documentation for initial instrument calibration and continuing instrument calibration verification to ensure that the data shall be of known quality and be appropriate for a given regulation or decision. This standard does not specify detailed procedural steps for calibration, but establishes the essential elements for selection of the appropriate technique or techniques. If more stringent standards or requirements are included in a mandated test method or by regulation, the laboratory shall demonstrate that such requirements are met. If it is not apparent which standard is more stringent, then the requirements of the regulation or mandated test method are to be followed.

b. Initial instrument calibrations. The following items are essential elements of initial instrument calibration:

(1) The laboratory shall include or reference the details of the initial instrument calibration procedures, including calculations, integrations, acceptance criteria and associated statistics in the standard operating procedure for the test method. When initial instrument calibration procedures are referenced in the test method, then the laboratory shall retain the referenced material and make it available for review.

(2) The laboratory shall retain sufficient raw data records to permit reconstruction of the initial instrument calibration (e.g., calibration date, test method, instrument, analysis date, each analyte name, analyst's initials or signature, concentration and response, calibration curve or response factor, or unique equation or coefficient used to reduce instrument responses to concentration).

(3) Sample results shall be quantitated from the initial instrument calibration and may not be quantitated from any continuing instrument calibration verification unless otherwise required by regulation, method, or program.

(4) All initial instrument calibrations shall be verified with a standard obtained from a second manufacturer or lot. Traceability shall be to a national standard, when available. This element does not apply to laboratories performing only simple test procedures.

(5) Criteria for the acceptance of an initial instrument calibration shall be established (e.g., correlation coefficient and relative percent difference). The criteria used shall be 0.995 or greater for the calibration coefficient unless a different criterion is included in the method being used.

(6) Results of samples not bracketed by initial calibration standards (within calibration range) shall be reported as having less certainty (e.g., defined qualifiers or flags or explained in the case narrative). The lowest calibration standard shall be above the detection limit.

(7) If the initial instrument calibration results are outside established acceptance criteria, corrective actions shall be performed. Data associated with an unacceptable initial instrument calibration shall not be reported.

(8) Calibration standards shall include concentrations at or below the regulatory limit or decision level, if these limits or levels are known by the laboratory, unless these concentrations are below the laboratory's demonstrated detection limits.

(9) If a reference or mandated method does not specify the number of calibration standards, the minimum number is two, not including blanks or a zero standard. The laboratory shall have a standard operating procedure for determining the number of points for establishing the initial instrument calibration.

c. Continuing instrument calibration verification.

(1) When an initial instrument calibration is not performed on the day of analysis, the validity of the initial calibration shall be verified prior to sample analyses by a continuing instrument calibration check with each analytical batch. This provision does not apply to laboratories performing only simple test procedures.

(2) The following items are essential elements of continuing instrument calibration verification:

(a) The laboratory shall include or reference the details of the continuing instrument calibration procedure, calculations and associated statistics in the standard operating procedure for the test method.

(b) The laboratory shall verify calibration for each compound, element, or other discrete chemical species, except for multicomponent analytes such as aroclors, total petroleum hydrocarbons, or toxaphene where a representative chemical related substance or mixture can be used.

(c) The laboratory shall perform a continuing instrument calibration verification as follows:

(i) At the beginning and end of each analytical batch. If an internal standard is used, only one verification needs to be performed at the beginning of the analytical batch;

(ii) Whenever it is expected that the analytical system may be out of calibration or might not meet the verification acceptance criteria;

(iii) If the time period for calibration or the most previous calibration verification has expired; or

(iv) For analytical systems that contain a calibration verification requirement.

(d) Sufficient raw data records shall be retained to permit reconstruction of the continuing instrument calibration verification (e.g., or test method, instrument, analysis date, each analyte name, concentration and response, calibration curve or response factor, or unique equations or coefficients used to convert instrument responses into concentrations). Continuing calibration verification records shall explicitly connect the continuing verification data to the initial instrument calibration.

(e) Criteria for the acceptance of a continuing instrument calibration verification shall be established (e.g., percent recovery or relative percent difference).

(f) If the continuing instrument calibration verification results obtained are outside established acceptance criteria, corrective actions shall be performed. If routine corrective action procedures fail to produce a second consecutive (immediate) calibration verification within acceptance criteria, then either the laboratory has to demonstrate acceptable performance after corrective action with two consecutive successful calibration verifications, or a new initial instrument calibration shall be performed. If the laboratory has not verified calibration, sample analyses shall not occur until the analytical system is calibrated or calibration verified. If samples are analyzed using a system on which the calibration has not yet been verified, the results shall be flagged. Data associated with an unacceptable calibration verification may be fully useable under the following special conditions:

(i) When the acceptance criteria for the continuing calibration verification are exceeded high (i.e., high bias) and there are associated samples that are nondetects, then those nondetects may be reported. Otherwise the samples affected by the unacceptable calibration verification shall be reanalyzed after a new calibration curve has been established, evaluated and accepted.

(ii) When the acceptance criteria for the continuing calibration verification are exceeded low (i.e., low bias) those sample results may be reported if they exceed a maximum regulatory limit or decision level. Otherwise the samples affected by the unacceptable verification shall be reanalyzed after a new calibration curve has been established, evaluated and accepted.

Historical Notes

Derived from Volume 25, Issue 07, eff. January 1, 2009; amended, Virginia Register Volume 32, Issue 22, eff. September 1, 2016.

Statutory Authority

§ 2.2-1105 of the Code of Virginia.