Suggested QC Practices for On-Line Analysis
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Transcript of Suggested QC Practices for On-Line Analysis
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Suggested QC Practices for On-Line Analysis �William Lipps Analytical & Measuring Instrument Division Shimadzu Scientific Instruments, Columbia, MD.
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Why Do We Need Continuous Monitoring?
Laboratory sampling is only a “snapshot” of the sample on a good day.
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Sampling At “The Pipe” Does Not Sample Storm or Irrigation Water
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Sources of Pollution May be Outside “The Pipe”
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Rarely Do We Sample When Rivers Are Flooding
Just one more bottle
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But There Are No USEPA Approved Methods For On-Line Analysis!
EPA approved methods include: • Sampling
• Preservation
• Calibration verification
• Duplicates
• Spikes
• LCS
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Can Get Around Sampling and Preservation…
Collection
Manual Sample
Preserve
Store
Analysis
Physical Treatment
Chemical Treatment
Measurement
Reporting
Report Generation
Review/React
…since analysis is immediate.
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No Lab Report is Created, No Batch QC
Analysis
Physical Treatment
Chemical Treatment
Measurement
Reporting
Report Generation
Review/React
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A Significant Portion of “Normal” is Eliminated
Analysis
Physical Treatment
Chemical Treatment
Measurement
Reporting
Review/React
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But a Method Includes “Batch” QC Steps That Must Be Done
Including: l Calibration and calibration verification
l Blanks
l Duplicates
l Matrix spikes
l Analysis of control samples
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Calibration of On-Line Analyzers Can Be Automated
l Methods should ensure that analyzers automatically recalibrate.
l Should use multiple points if necessary
l Or, operators should periodically recalibrate.
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Calibration Verification Should Be Automated
l Methods should ensure that analyzers automatically verify the calibration in a fixed interval.
l Failed CCV should repeat calibration or flag
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Analyzer Should Run “Blanks” If Target Analyte Varies
Process control blanks
Ambient water blanks
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The Concept of “Duplicates” Does Not Apply…
• The on-line method should require a way to collect repeatability data
• Stick the sampling straw in a beaker
…however, precision should be evaluated
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The Concept of “Spikes” Does Not Apply…
• The on-line method should require a way to determine recovery in the matrix
• Recovery determined on commissioning
…however, recovery should be evaluated
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The Concept of “LCS” Does Not Apply…
• The on-line method should periodically evaluate an LCS
• LCS defined as comparison to approved method
…however, precision and recovery should be evaluated
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Example of TN (On-Line) Compared to TKN (Approved)
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Aver
age
Tota
l Nitr
ogen
(m
g/L/
day)
Date
TKN vs TN TKN
TN
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Example of TKP (Approved) Compared to TP (Online)
TPK vs TP
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Date
Ave
rage
Tot
al
Phos
phor
us (m
g/L/
day)
TP ManualTP
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On-Line Monitoring Allows You To See “Upsets”
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Relat
ive T
P (mg
/L)
Date
Biweekly Monitor
Hourly Monitor
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2
3
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8:32 19:32 6:32 19:32 6:32 18:32 16:32 14:32Time (Hrs)
Rela
tive
TP (m
g/L)
Laboratory
On-line
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Any New “Method” For Continuous On-Line Monitoring Should:
l Obtain equivalent results to approved laboratory methods
l Be “rugged”
l Use few reagents
l Have a sufficient range
l Sample/”handle” a complex matrix
l Calibrate with multiple points
l Require periodic check samples compared to lab
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On-Line Analyzer Must Be Rugged Enough For Field / Plant Use
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The On-Line Analyzer Should Be Capable of Sampling Multiple Streams
Multi-Stream Sample Switching Unit
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The On-Line Analyzer Should Be Capable of Handling TSS, If Needed
Multiple Stream TSS Unit
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Benefits of On-Line Monitoring
Achieve Maximum Efficiency
• Faster response • Better treatment • Cost reduction
Reduce
• Labor • Time • Money
Flexibility of Sampling
• Hourly • Daily • Weekly • Monthly
Automatic
• Sampling • Pretreatment • Digestion • Analysis • Report
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On-Line Analyzer Methods Are Needed If Data Is Reported For Compliance
l Some QC in existing methods does not apply.
l New methods can be written that still provide sufficient QC.
l On-line results should be compared to lab results.
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