Mentoring Session

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Method Modifications

• Mentoring Session
• Technical Assistance Committee

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TNI Training Disclaimer

• The material presented in this session is for
  informational purposes only. It is designed to
  promote understanding, consistency and
  clarification of technical and accreditation
  requirements. It should not be considered a
  change or alteration of the Accreditation
  standards, the published methods, a regulatory
  agency requirement or a position of TNI.

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Method Modifications

• The primary objective of method
• modifications is to enhance precision and
• accuracy for each analysis.

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• All laboratories large and small
• Such as commercial and private (including
  municipalities) must prove that their method
  modification to any approved standard analytical
  method is valid.

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What to Document

• The information and supporting data, required
  during the validation, must be sufficient to
  allow an independent reviewer (EPA, state or
  contractor) to verify each determination and
  calculation performed by the laboratory.

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Modifications

• Where more than one matrix type is involved
  (e.g., air, soil, water, sludge)
• The laboratory must validate the method on each
  matrix type.
• In most cases several different samples should be
  involved in the validation,
• Example Non-Potable Water several effluent
  samples from different plants should be used.

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Method Modifications

• Validation Criteria
• Must include the documented procedure used to
  validate and report the data
• Should explain the statistical analysis of study
  results.
• Must include all raw data results to allow for a
  complete independent reviewer verification
• Should be checked by comparing the performance
  criteria with the actual approved standard
  method, as written.

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Quality Control

• What is involved?
• Initial Precision and Recovery
• Calibration (initial and continuing)
• Method Detection Limit (MDL),
• Laboratory fortified blank
• Matrix Spikes
• Method Blanks

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Quality Control

• Internal standard/s
• Surrogate standard/s
• Tracer (for radiochemistry)
• Control charts or other trend analyses
• Quality Control acceptance criteria

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Raw Data

• Sample numbers or other identifiers used
• Sample preparation (extraction/digestion) dates
• Analysis dates and times
• Sequence of analyses or run logs
• Sample volume

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Raw Data

• Extract volume prior to each cleanup step
• Extract volume after each cleanup step
• Final extract volume prior to injection
• Digestion volume
• Titration volume

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Raw Data

• Percent solids or percent moisture
• Dilution data - differentiating between dilution
  of a sample and dilution of an extract
• Instrument(s) and operating conditions, such as
• GC and/or GC/MS including detailed
  information on columns used for determination and
  confirmation (column length and diameter,
  stationary phase, solid support, film thickness,
  etc.) In addition, analysis conditions
  (temperature programs, flow rates, etc.) must be
  documented
• Detectors type, operating conditions, etc.
• Chromatograms ion current profiles, bar graph
  spectra, library search results , etc

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Raw Data

• Data Quantitation reports, system outputs, and
  other data to link the raw data to the results
  reported. (Where these data are edited manually,
  explanations of all manual changes must be
  included)
• Direct instrument readouts strip charts, printer
  tapes, etc., and other data to support the final
  results

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Raw Data

• Laboratory bench sheets and copies of all
  pertinent logbook pages for all sample
  preparation, cleanup, and determinative steps of
  the analysis
• Dilution data - differentiating between dilution
  of a sample and dilution of an extract

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Example 1
When using 1000 mL sample, the pipet used in the
method is a 25 mL wide bore, this would take an
analyst 40 separate measurements to deliver the
volme

• Standard Methods 2540 D.
• Total Suspended Solids
• Sample Analysis
• 3 (b) states to stir the sample and pipet an
  aliquot from the midpoint of the container

Modification Using a graduated cylinder (1000
ml) instead of the 25mL pipet, reduces analyst
time and handling of the sample
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Example 2

• The use of an alternate QA/QC chemical in place
  of the Glucose/Glutamic Acid (GGA) for BOD/CBOD.
• Laboratories that are using KHP (Potassium
  Hydrogen Phthalate) for their BOD/CBOD depletion
  chemical.
• Does the laboratory have the right to modify the
  method to a degree of changing the chemistry?

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References

• 40 CFR 136.6 Method modifications and
  analytical requirements.
• Flexibility to Modify CWA Method Nov 20, 2007
• EPA Solutions to Analytical Chemistry Problems
  with Clean Water Act Methods 2007 (Pumpkin Book)
• (EPA 821-B-98-002 EPA Approval of Alternate Test
  Procedures for Organic and Inorganic Analytes in
  Wastewater and Drinking Water March 1999)

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