Section 760. Quality control requirements

A. General.

1. The quality control protocols specified by the laboratory's SOPs shall be followed (1VAC30-45-730 C). The laboratory shall ensure that either the (i) applicable essential standards outlined in this section through 1VAC30-45-775, 1VAC30-45-790 through 1VAC30-45-798, and 1VAC30-45-810 through 1VAC30-45-818 or (ii) mandated methods or regulations, whichever are more stringent, are incorporated into their method SOPs. When it is not apparent which is more stringent, the quality controls in the mandated method or regulations are to be followed.

2. All quality control measures shall be assessed and evaluated on an ongoing basis and quality control acceptance criteria shall be used to determine the validity of the data. The laboratory shall have procedures for the development of acceptance/rejection criteria where no method or regulatory criteria exists.

B. Initial test method evaluation. For all test methods other than microbiology, the requirements of subdivisions 1 and 2 of this subsection apply. For microbiology testing, the initial test method evaluation requirements are contained in 1VAC30-45-790 through 1VAC30-45-798. For the evaluation of precision and bias (subdivision 3 of this subsection), the requirements of subdivision 3 a of this subsection apply to standard methods. The requirements of subdivision 3 b of this subsection apply to the methods referenced in that subdivision.

1. Limit of detection (LOD).

a. The laboratory shall determine the LOD for the method for each target analyte of concern in the quality system matrices. All sample processing steps of the analytical method shall be included in the determination of the LOD.

b. The validity of the LOD shall be confirmed by qualitative identification of the analyte or analytes in a quality control sample in each quality system matrix containing the analyte at no more than two to three times the LOD for single analyte tests and one to four times the LOD for multiple analyte tests. This verification shall be performed on every instrument that is to be used for analysis of samples and reporting of data.

c. An LOD study is not required for any component for which spiking solutions or quality control samples are not available such as temperature, or, when test results are not to be reported to the LOD (versus the limit of quantitation or working range of instrument calibration), according to 1VAC30-45-771 and 1VAC30-45-814. Where an LOD study is not performed, the laboratory may not report a value below the limit of quantitation.

2. Limit of quantitation (LOQ).

a. The laboratory shall determine the LOQ for each analyte of concern according to a defined, documented procedure.

b. The LOQ study is not required for any component or property for which spiking solutions or quality control samples are not commercially available or otherwise inappropriate (e.g., pH).

c. The validity of the LOQ shall be confirmed by successful analysis of a QC sample containing the analytes of concern in each quality system matrix one to two times the claimed LOQ. A successful analysis is one where the recovery of each analyte is within the established test method acceptance criteria or client data quality objectives for accuracy. This single analysis is not required if the bias and precision of the measurement system is evaluated at the LOQ.

3. Evaluation of precision and bias.

a. Standard methods. The laboratory shall evaluate the precision and bias of a standard method for each analyte of concern for each quality system matrix according to either of the following:

(1) The single-concentration four-replicate recovery study procedures in 1VAC30-45-730 F; or

(2) An alternate procedure documented in the quality manual when the analyte cannot be spiked into the sample matrix and quality control samples are not commercially available.

b. Nonstandard methods.

(1) For laboratory-developed test methods or nonstandard test methods that were not in use by the laboratory before July 2003, the laboratory shall have a documented procedure to evaluate precision and bias. The laboratory shall also compare results of the precision and bias measurements with criteria given in the reference method or criteria established by the laboratory.

(2) Precision and bias measurements shall evaluate the method across the analytical calibration range of the method. The laboratory shall also evaluate precision and bias in the relevant quality system matrices and shall process the samples through the entire measurement system for each analyte of interest.

(3) The following are examples of a systematic approach to evaluate precision and bias:

(a) Example 1. Analyze QC samples in triplicate containing the analytes of concern at or near the limit of quantitation, at the upper-range of the calibration (upper 20%) and at a mid-range concentration. Process these samples on different days as three sets of samples through the entire measurement system for each analyte of interest. Each day one QC sample at each concentration is analyzed. A separate method blank shall be subjected to the analytical method along with the QC samples on each of the three days. (Note that the three samples at the LOQ concentration can demonstrate sensitivity as well.) For each analyte, calculate the mean recovery for each day, for each level over days, and for all nine samples. Calculate the relative standard deviation for each of the separate means obtained. Compare the standard deviations for the different days and the standard deviations for the different concentrations. If the different standard deviations are all statistically insignificant (e.g., F-test), then compare the overall mean and standard deviation with the established criteria from above.

(b) Example 2. A validation protocol such as the Tier I, Tier II, and Tier III requirements in U.S. EPA Office of Water's Alternate Test Procedure (ATP) approval process.

4. Evaluation of selectivity. The laboratory shall evaluate selectivity by following the checks established within the method. These checks may include mass spectral tuning, second column confirmation, ICP inter-element interference checks, chromatography retention time windows, sample blanks, spectrochemical absorption or fluorescence profiles, co-precipitation evaluations, and electrode response factors.

Historical Notes

Derived from Volume 25, Issue 07, eff. January 1, 2009; amended, Virginia Register Volume 32, Issue 22, eff. September 1, 2016; Errata, 32:24 VA.R. XXX July 25, 2016.

Statutory Authority

§ 2.2-1105 of the Code of Virginia.