Laboratory QA/QC and Calibration
Laboratory QA/QC and Calibration
Quality assurance establishes a controlled system; quality control provides evidence that individual measurements and analytical batches perform acceptably.
## 1. Essential quality-control samples | QC item | Purpose | |—|—| | Method blank | Detect contamination introduced during preparation and analysis | | Calibration blank | Check baseline response and contamination | | Calibration standards | Establish instrument response across a defined range | | Continuing calibration verification | Confirm calibration remains valid during a batch | | Laboratory control sample | Assess method performance using a known material | | Matrix spike | Evaluate analyte recovery in the sample matrix | | Duplicate | Evaluate precision | | Certified reference material | Compare measured values with an independent assigned value |
## 2. Calibration control Record instrument ID, calibration date/time, standard identity and lot, expiry, concentrations, calibration model, working range, acceptance criteria and verification results. Do not extrapolate beyond the validated calibration range without an approved procedure.
## 3. Precision and recovery Relative percent difference (RPD) is commonly used to compare duplicate results when appropriate:
[ RPD(%)= ]
Percent recovery is commonly expressed as:
[ Recovery(%)= ]
Apply the formula and acceptance range specified by the method or laboratory quality system; do not apply a universal pass/fail threshold.
## 4. Result validation Review calibration, blanks, control samples, duplicates, spike recovery, detection limits, dilution, calculations, units, qualifiers, transcription and instrument flags. Investigate QC failures before releasing affected results.
## 5. Data qualifiers Use controlled qualifiers to explain estimated, rejected, below-limit, diluted or otherwise qualified results. Preserve the original result and document any reanalysis or correction.
## 6. Corrective action Define how the laboratory handles failed calibration, blank contamination, unacceptable recovery, carryover, instrument malfunction and sample integrity issues. Record impact assessment, reanalysis decision and authorization.