This document discusses the need for continuous online water quality monitoring and proposes best practices for quality control of online analysis methods. It notes that traditional EPA-approved laboratory methods do not fully apply to online monitoring due to differences in sampling and analysis. The document suggests that new online analysis methods ensure equivalent results to standard methods through periodic calibration verification, evaluation of precision and recovery, and comparison to laboratory analyses. Regular quality control would allow online monitors to provide more frequent, flexible water quality data for process control and compliance reporting.

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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)
0
10
20
30
40
50
11/19/04 11/29/04 12/9/04 12/19/04 12/29/04 1/8/05
AverageTotalNitrogen
(mg/L/day)
Date
TKN vs TN TKN
TN

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Example of TKP (Approved)
Compared to TP (Online)
TPK vs TP
0
1
2
3
4
5
6
7
11/19/04 11/29/04 12/9/04 12/19/04 12/29/04 1/8/05
Date
AverageTotal
Phosphorus(mg/L/day)
TP Manual
TP

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On-Line Monitoring Allows You To
See “Upsets”
0
1
2
3
4
5
6
7
10/4/2004 10/24/2004 11/13/2004 12/3/2004 12/23/2004
RelativeTP(mg/L)
Date
Biweekly Monitor
Hourly Monitor
0
1
2
3
4
5
6
8:32 19:32 6:32 19:32 6:32 18:32 16:32 14:32
Time (Hrs)
RelativeTP(mg/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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