Appendix D - Quality Control >>

Appendix C - Quality Assurance

Reference:
Dux, James P. Handbook of Quality Assurance for the Analytical Chemistry Laboratory. 2nd Edition. Van Nostrand Reinhold. New York, NY.

Quality control (QC) refers to those laboratory operations used to ensure that the data generated by the laboratory are of known accuracy to some stated, quantitative degree of probability. This means that every laboratory should be able to attach to every result a range within which the true value of the analyte can be stated to lie with a certain degree of confidence. The range is called a confidence limit with a specified probability. This does not mean that the confidence limit must be reported with the result, but that the laboratory should be able to make this statement, if required.

The kinds of operations referred to in this definition are those that are generally applied as good scientific practice: instrument calibration, personnel training, use of pure reagents, use of standards and reference materials, etc.

Quality assurance (QA) refers to the ability of the laboratory to demonstrate or prove to someone not working in the laboratory that the quality of the data is what the laboratory says it is. Quality assurance is those laboratory operations undertaken to achieve the following objectives of documentation:

1. That quality control procedures are being implemented in the laboratory. For example, quality control requires that all pH meters be calibrated before use; quality assurance requires that the fact shall be recorded that the meter was calibrated and the results obtained.
2. Assure the accountability of the data is maintained. "Accountability" means that the data reported do, in fact, reflect the sample as it was received in the laboratory, i.e. that mix-up was avoided and the sample was properly preserved prior to analysis.
3. Facilitate traceability of an analytical result. Every result reported should be traceable to the date of analysis, the analyst who ran the sample, the method used, the instrument(s) used and its (their) condition, and the status of the analytical system at the time of the analysis.
4. Ensure that reasonable precautions are taken to protect the raw data against loss, damage, theft, or tampering.

The establishment, maintenance and enforcement of QA/QC programs in the laboratory is the responsibility of laboratory management.

The checklist below can serve as a guide for a quick review of the status of quality assurance practices in the laboratory.

• Information on standards
• source purity or activity
• preparation
• adequate labeling
• storage method
• date received
• date prepared
• lot number
• identity of preparer
• certification information
• review and acceptance
• acceptance criteria
• Laboratory sample handling/preparation
• protocol for sample log-in
• protocol for sample preservation
• protocol for sample pretreatment (drying, grinding, etc)
• protocol for sample storage
• protocol for sample disposal
• Analytical methods
• selection of analytical method
• source (AOAC, AACC, AOCS, etc) evaluation of analytical methods
• validation reference materials or samples
• spiked samples replicate analysis
• negative control checks (blanks)
• comparison to established method
• ruggedness testing
• method documentation
• reference
• scope - applicability of method
• principle of method
• equipment/apparatus needed
• identification of safety precautions
• procedure
• comments
• calculations
• review and approval

Quality control calculation checks: must include spike and recovery and replicate analysis scheme; must be uniform for all samples of a given type and method.

systematic series of negative controls: blanks must be specified, i.e. reagent blanks, method blanks

performance evaluation samples (check samples): recommended for method, matrix, analyte customarily performed; these are not substitutes for regular controls but are used in addition to regular spikes and/or reference materials.

control charts

• type
  • X charts
  • Spiked-sample control charts
  • R-charts
• charts should be established for the analyte, matrix, and concentration of interest; results should be readily available.
• limits/acceptance criteria should be established blind samples

• Reporting of results units must be specified records must be kept for a specified time timeliness: dates and times of analysis must be recorded and available significant figures must be correct form for reporting data must be uniform report must be reviewed for correctness
• Instruments, equipment, materials specifications met when purchased to perform task preventative maintenance and control calibration
  • type
  • frequency
• Personnel resumes should be on record. on-the-job training should be listed.
• Standard operating procedures analytical methods (see above)
  • calibration of equipment and glassware
  • preparation of reagents
  • quality control procedures
  • data reporting procedures
  • personnel safety, training and evaluation
  • documentation of sample receipt, tracking,
  • storage, and final disposition
  • scheme for data document storage, archiving, and retrieval
  • equipment and instrument operation and maintenance
  • waste disposal
• Corrective action

Appendix D - Quality Control >>

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