Quality Assurance / Quality Control (QA/QC) Systems – Guiding Principles

As part of our ongoing commitment to producing quality results, Lambton Scientific follows a systematic approach to batch analytics. Analytical runs follow a pattern as can be seen the figure below.

QA/QC Runs and Response

  1. Initial Calibration
    • Calibration Standards can consist of the following:
      1. Prepared in-house:
        • Documented in "Reagent Preparation Log Book"
        • "Critical Components" must have a supplier Certificate of Analysis
        • All other ingredients must be ACS grade or better
        • Any gravimetric weighing to be at least 2 significant digits (by difference), 2 or 4 preferred
        • Prepared using DI waster (18 Mohms-cm)
        • Use Trace Metals grade acids (if required)
        • Use virgin and/or pre-rinsed storage containers
      2. Purchase Standards:
        • Must be traceable to a Standard Reference Material (NIST preferred)
        • Documented Certificates of Analysis
    • Calibration Standards are:
      • Typically analyzed from lowest to highest concentration
      • Have the lowest concentration standard to be 5 - 10 times the MDL
      • Have the highest concentration less than the maximum linearity value
      • Have concentrations with no more than one order of magnitude between concentrations (i.e. 1, 10, 100, 1000, etc)
    • For nonlinear curves (i.e. quadratics) - minimum of five standards (plus blank)
    • For linear curves:
      • Minimum of three standards (plus blank)
      • Mininum acceptable correlation coefficient value is 0.995
    • Treatment of intercepts:
      • For positive intercepts:
        • Leave as a positive intercept, however, the calculated concentration must not exceed 2 x MDL
      • For negative intercepts:
        • Force the regression thru origin

  2. Batch 1 of Analytical Run
    • Length of batch is dictated by the Reference Method (typically between 10 and 20 samples)
    • QA/QC of Batch 1:
      • Instrument Blank (IB)
      • External Reference (QCS - Quality Control Start of Run)
        • Calibration Standards and QA/QC samples must be completely independent of each other
          • Preferably, use standards/reagents from different suppliers
          • Alternately, use standards/reagents from a single supplier, but different lot numbers
      • Method Blank (MB)
      • Spiked Blank (SB)
      • Sample 1 (S1)
      • Sample 1 Replicate (S1 REP)
        • must be completely independent from Sample 1 and follow all analytical steps
      • Sample 1 Matrix Spike (S1 SPK)
        • A known concentration of the target analyte added to sample
      • Sample 1 Matrix Spike Duplicate (S1 SPK DUP)
        • As above and must be completely independent from Sample 1 Matrix Spike
    • Remaining of Batch 1
      • Samples 2 - 10 (S2..S10)
      • Continuing Calibration Verification (CCV)
        • A periodic confirmation, by analysis of a certified external standard (near midpoint of range) that the instrument performance has not change significantly (typically within 10%) from the initial calibration

  3. Batch 2 of Run
    • QA/QC of Batch 2
      • As above
    • Remaining of Batch 2
      • As above
      • External Reference (QCE - Quality Control End of Run)

Lambton Scientific's Typical Rules of Quality Control:

  • Maximum intercept (b) is 2 x MDL
  • Minimum correlation coefficient (r²) is 0.995
  • External Reference Target Limit is 10% (90-110% of Target) - see QA/QC Charting
  • External Reference Relative Percent Difference (RPD) is 10%
  • Sample Replicates must be within 10% of average
  • Matrix Spike must be within 20% of original sample value
  • Calculated concentrations must not be more than 10% extrapolated beyond the top of the calibration curve


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