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Mercury Monitoring. The FDEP Laboratory Perspective. Timothy W. Fitzpatrick (850) 245-8083 [email protected] Considerations: Compliance versus Environmental Monitoring. Sample Kit Preparation Sampling Protocols Laboratory Design Analytical Rigor Data Interpretation.

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Mercury Monitoring

The FDEP Laboratory Perspective

Timothy W. Fitzpatrick

(850) 245-8083

[email protected]

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Considerations:Compliance versus Environmental Monitoring

  • Sample Kit Preparation

  • Sampling Protocols

  • Laboratory Design

  • Analytical Rigor

  • Data Interpretation

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FDEP’s Experience

  • Constructed Class 1000/100 in mid-1990s;

  • Adopted Method 1631 w/ some modifications from initial EPA version (semi-automated the method, investigated aqua regia digestion);

  • Developed fully automated methylmercury analysis in late 1990s using direct ethylation P&T GCAF;

  • EPA incorporated semi-automated advances in Method 1631E; Automation of Draft Method 1630 under evaluation by EPA Region IV;

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FDEP’s Experience

  • Primary Client Focus: Environmental Monitoring and Research

  • Detection Limits:

    THg ~ 100 pg/L (0.10 ng/L)

    MeHg ~ 20 pg/L (0.02 ng/L)

  • Initiated Everglades Mercury Round Robins ca. 2000

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Introduction to Method 1669

  • “Clean hands/dirty hands” sampling

  • Ultra-trace detection levels and methods

    • Tables listing applicable levels in sampling methods

  • “Mindset” and technique

    • Protection of sample against contamination

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Sampling Kits

  • Double Bagged, Pre-Cleaned Vessels of Glass, Teflon or Surface Fluorinated P-E Prepared in Laboratory

  • Prices: Glass < Fluor. PE <<< Teflon

  • Pre-Cleaned Sampling Equipment May Be Needed (Teflon Tubing, Silicon Pump Tubing, Filtration Devices, etc.)

  • Laboratories are Sources of Contamination! (Air, DI Water, Reagents, etc.)

  • Clean Benches or Clean Room Strongly Recommended for Equip. Preparation (Absolute Necessity for Environ. Monitoring)

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Sampling by Method 1669

  • Performance Based Method

  • Compliance vs. Environmental Monitoring: When is the Full-Blown Method Necessary (or Practical)?

  • Our Experience w/ Hg – Most Contamination Occurs in the Laboratory

  • Vessels Need to be Prepared in a ‘Clean’ Laboratory Environment

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Sample Collection SOP

  • DEP SOP FS 8200


  • Adapted from EPA 1669

  • “Performance-based” concept

  • Verify performance with blanks & other QC

  • Sampling team practice recommended

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Field Contamination Issues

  • Source of analyte-free water for field blanks and equipment blanks

  • Sampling equipment and sample containers

  • Sampling personnel and clothing

  • Ambient sampling environment

  • Sampling techniques

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Sampling Equipment Decontamination

  • Minimum amount of pre-cleaned equipment (only) recommended ;

  • Controlled environment for cleaning;

  • See FS 8200 cleaning procedures;

    • Specific cleaning procedure for mercury;

  • All pre-cleaned items wrapped for field use;

  • Field-based cleaning not recommended;

  • Dippers not recommended; Collect directly into sample bottles where possible;

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On-site Precautions

  • All equipment and supplies in covered storage until use

  • Keep hands and equipment away from contamination sources

  • Adhere to “clean hands/dirty hands” protocols

  • Change gloves when needed

  • Collect least contaminated source first

    Develop a ‘contamination sensitive’ mindset

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Precautions for Sampling Equipment & Protective Clothing

  • Caution advised with pigmented materials, bottle labels, ink

  • See FS 8200 for recommended sampling equipment and materials to avoid

  • Wrap cleaned pump tubing ends

  • Don’t contaminate tubing with pump or extension device

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Sample Preservation & Transport

  • Add HCl preservative upon return to lab

  • Max of 48 hours on ice prior to preservative

  • Protect bagged samples from contamination during transport and storage

  • Isolate or segregate samples as needed

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1669/245.1 - Conventional Preparation @ SFWMD; Analysis using pre-concentration CVAAS; MDL = 50 ng/L

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Laboratory Design Considerations: Clean Bench vs. Clean Lab using pre-concentration CVAAS; MDL = 50 ng/L

  • Cost vs. Type of Work Envisioned

  • Workload Issues

    Sampling Bottle and Equipment Preparation

    Sample Preparation and Determinative Steps

  • Fugitive Vapor Control

  • Particulate Control

  • Instrument Location

    Without proper controls, spurious laboratory contamination can exceed water quality standards!

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Instrument Schematic using pre-concentration CVAAS; MDL = 50 ng/L

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Blanks in 1631 using pre-concentration CVAAS; MDL = 50 ng/L

  • Blanks play a critical role in monitoring contamination, and quantifying the mercury content of samples

  • Mercury levels in (digested) method blanks may be higher than those present in ambient samples

  • Even the best de-ionized water has measurable concentrations of mercury

  • Digested blanks have Hg concentrations between 0.2 and 0.6 ng/L

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Blanks in 1631E using pre-concentration CVAAS; MDL = 50 ng/L

  • Confounding of mercury levels in the reagent and the de-ionized water – cannot easily separate mercury content of reagents from mercury in de-ionized water

  • Assumption: Most of the “background contamination” in method blanks is from the reagents and not from the DI water

  • No “bubbler blanks” used in the automated method

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Quantification in 1631E using pre-concentration CVAAS; MDL = 50 ng/L

  • Analyze 5 method blanks and calculate the blank correction

  • Subtract this “blank correction term” from all samples

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Sensitivity Requirements using pre-concentration CVAAS; MDL = 50 ng/L

Natural Waters

Typical Levels:

0.5 – 2 ng/L THg

< 0.02 – 0.2 ng/L MeHg

Recommended Quantitation Limits:

~ 0.5 ng/L THg

~0.05 ng/L MeHg

Discharge Monitoring

Water Quality Standards:

12 ng/L THg Fresh

25 ng/L THg Marine

Recommended Quantitation Limits:

< 10 ng/L THg Fresh

< 25 ng/L THg Marine

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Data Interpretation using pre-concentration CVAAS; MDL = 50 ng/LDetection and Quantitation

Detection Limit and Quantitation Limits are Influenced by:

  • Sampling vessels, collection and handling techniques

  • Quality of the laboratory environment – particulate content of laboratory air

  • Cleanliness of digestion reagents and procedure

  • Instrumental technique

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Data Interpretation using pre-concentration CVAAS; MDL = 50 ng/LRecommendations

  • Conduct on-going, long-term detection limit studies rather than one-time studies;

  • Confirm all water quality exceedances with a separate analysis;

  • Use multiple method blanks with each analytical preparation batch;

  • Use rigorous quality control measures to ensure data integrity;