CALFED/California Bay-Delta Authority Mercury Studies Quality Assurance Oversight Program Results...

CALFED/California Bay-Delta AuthorityMercury Studies

Quality Assurance Oversight ProgramResults from Intercomparison Study 2

November 2005

Presented by: Beverly H. van Buuren

February 22, 2006

San Francisco Estuary InstituteThird Annual Mercury Coordination Meeting

Regional Water Quality Board, Oakland, California

van buuren consulting, llcwww.vanbuurenconsulting.comslide# 2

Data that supports Decisions

QA Oversight Program Goals

Performance RequirementsLinked to

Program Goals

Develop Comparability Between Hg Projects

Build Comparabilitywith other Programs

Data of Known and Documented Quality

QA/QC Tools & Systems to Improve Efficiency


How Intercomparison Studies Help

• Comparability of Data (bias)– within current project schedule– year-to-year– other programs?

• Alerts program/project/method/lab issues

• Individual Lab Performance (esp. CRMs)

• Data of Known and Documented Quality

• CBDA since March 2000 (6 years!)


Intercomparison Study Schedule

Analyte and Matrix Date Samples Ship Date Final Report

THg Water

MMHg SedimentJune 2005

April 2006

April 2007

Nov. 2005

June 2006

June 2007THg Water

MMHg Water

THg Tissue

MMHg Tissue

THg Sediment

MMHg Sediment

Nov. 2005

Nov. 2006

July 2007

March 2006

Feb. 2007

Nov. 2007


Intercomparison Study 2

Analyte and Matrix Sample Concentration

THg Water spiked lake water 5.56 ng/L

THg Sediment IAEA-SL-1 130 ng/g

THg Tissue IAEA-407 222 ng/g

MMHg Water spiked lake water 0.173 ng/L

MMHg Sediment ERM-CC580 75 ng/g

MMHg Tissue IAEA-407 200 ng/g

• 4 laboratories plus the referee lab

• samples shipped 11/17, results back 01/15, draft report 03/06


Evaluation of Laboratory Results

Ιz-scoreΙ Versus Reference Value

Rating

≤2 ±10% Very Good

>2 and ≤5 >10% and <25% Good

>5 >25% Poor


THg in Water Results

Laboratory Intercomparison Study Summary Total Mercury in Freshwater QC

Parameter Lab A Lab B Lab C Lab D Lab E

Freshwater Reference Material

Mean Value

5.90 ng/L 1.3% RSD

n = 3

5.62 ng/L 0.1% RSD

n = 3

5.19 ng/L 4.1% RSD

n = 3

5.05 ng/L 2.7% RSD

n = 3

4.19 ng/L 2.2% RSD

n = 3

Ι z-score Ι 1.223 0.204 1.343 1.823 4.916

ratings very good very good very good very good good

QA group and lab E are investigating systematically low-bias results to assess significance and causes


MMHg in Water Results

Laboratory Intercomparison Study Summary Methyl Mercury in Freshwater QC


Freshwater Reference Material

Mean Value

0.175 ng/L 12% RSD

n = 3

0.158 ng/L 6.8% RSD

n = 3

0.15 ng/L 3.9% RSD

n = 3

0.194 ng/L 4.7% RSD

n = 3

0.201 ng/L 2.8% RSD

n = 3

Ι z-score Ι 0.231 1.696 3.044 2.466 3.237

ratings very good very good good good good

Difference between reference value and all lab results was less than 3 times the MDL (0.020 ng/L)


THg in Sediment Results

Laboratory Intercomparison Study Summary Total Mercury in Sediment QC


Sediment Reference Material

Mean Value

119 ng/g 0.8% RSD

n = 3

129.5 ng/g 0.8% RSD

n = 3

120.3 ng/g 0.5% RSD

n = 3

114.7 ng/g 0.9% RSD

n = 3

100.9 ng/g 1.9% RSD

n = 3

Ι z-score Ι 1.692 0.077 1.487 2.354 4.477

ratings very good very good very good good good

All laboratories employed different analytical methods, however results indicate good comparability of data


MMHg in Sediment ResultsLaboratory Intercomparison Study Summary

Methyl Mercury in Sediment

Lab

QC Parameter

Lab A Lab B Lab C Lab D Lab E


Mean Value

66.1 ng/g 5.7% RSD

n = 3

70.9 ng/g 20.2% RSD

n = 3

112.3 ng/g 46.5% RSD

n = 3

75.5 ng/g 22.3% RSD

n = 3

83.1 ng/g 9.7% RSD

n = 3

Ι z-score Ι 2.364 1.106 9.956 0.145 2.151

ratings good very good poor very good good

Significant high-bias in lab C results likely due to artifact resulting from distillation method. Other labs use extraction method.


THg in Tissue Results

Laboratory Intercomparison Study Summary Total Mercury in Tissue QC



Mean Value

246 ng/g 2.1% RSD

n = 3

235.7 ng/g 2.4% RSD

n = 3

240.3 ng/g 0.2% RSD

n = 3

no results submitted

no results submitted

Ι z-score Ι 2.162 1.237 1.652 n/a n/a

ratings good very good very good n/a n/a

Lab A “good” very close to “very good”

Lab D and lab E do not perform THg tissue analysis for this project


MMHg in Tissue Results

Laboratory Intercomparison Study Summary Methyl Mercury in Tissue

Lab

QC Parameter

Lab A Lab B Lab C Lab D Lab E


Mean Value

176 ng/g 1.1% RSD

n = 3

200.2 ng/g 3.0% RSD

n = 3

186 ng/g 4.6% RSD

n = 3

193 ng/g 1.7% RSD

n = 3

217 ng/g 4.3% RSD

n = 3

Ι z-score Ι 2.400 0.023 1.367 0.653 1.667

ratings good very good very good very good very good

Study results indicate good comparison of MMHg in tissue results across all participating labs


Closing Remarks• The MMHg in sediment results submitted by lab C highlight the

potential problem associated with the distillation of sediment samples…high-bias resulting from the methylmercury artifact. Projects using this method should have a specific plan for assessing if this method is appropriate to meeting project objectives (the QA group can help).

• One intercomparison study with only one sample per analyte/matrix combination is not statistically significant.

• Based on the results of this intercomparison study, comparability of data generated by laboratories is good across all matrix/analyte combinations.


Contact Information

Beverly H. van BuurenQA [email protected] Buuren Consulting, LLC4320 Baker Avenue NorthwestSeattle, WA 98107(206) 781-1692

Other projects we’re working on:

Surface Water Ambient Monitoring Program

Training classes for Monitoring Design and QA/QC

Holding Time Study on Low-level Nutrients

Appropriate QA/QC for Physical Habitat and Bioassessment Studies

Intercomparison for Pyrethroids in Sediment

QA/QC for Citizen Monitoring

QAPP Review for the SWRCB DFA

SWRCB OIT CIWQS Database

Expert Software System to draft QAPPs

mailto:[email protected]


Milestone DMA-80 Hg Analyzer

• Commercially available automated mercury analyzer

• Uses thermal decomposition of sample followed by amalgamation onto gold trap and atomic absorption spectrophotometry (AAS)

• Used for total mercury analysis of tissues and sediments

• EPA Method 7473 was developed to cover analysis of THg using this instrument


QA Considerations for the DMA-80

• Currently 3 laboratories participating in the program use this analyzer

• EPA Method 7473 is vague regarding important practical details (such as how to perform matrix spikes)

• Other QC parameters such as instrument calibration and accounting for carryover contamination must be detailed so they conform to the QC requirements of the CBDA Mercury Program

• Important to address QC issues without losing benefit of analysis with this instrument (savings in time/labor)


Resolution of QC questions for DMA-80

• Spoke with Milestone applications chemist, Dr. Skip Kingston, and Wes Heim (MLML) to resolve questions and develop QA policies

• Calibration will consist of 10-point “primary calibration” performed every 2 weeks and 5-point “daily calibration performed before an analytical run

• Matrix spikes can be performed by addition of standard directly to sample boat


Resolution of QC questions for DMA-80

• Carryover contamination can occur after running greater than 250ng of Hg through the analytical system

• Results will be reviewed after analysis to identify potential carryover


Evaluation of Laboratory Results

• Performance is evaluated through the use of z-scores

lab = the mean of the three values reported by the participating laboratory

• xref = the reference value established for the study ref = 0.05* xref to evaluate results 10% from the

reference value

ref

reflab xscorez

CALFED/California Bay-Delta Authority Mercury Studies Quality Assurance Oversight Program Results...

Documents

Transcript of CALFED/California Bay-Delta Authority Mercury Studies Quality Assurance Oversight Program Results...