qa/qc considerations for sampling and analysis associated with epa method 1631 chuck wibby wibby...
TRANSCRIPT
QA/QC Considerations for Sampling and Analysis
Associated with EPA Method 1631
Chuck WibbyWibby Environmental
Seminar on Low Level Mercury Data and Analyses
Boulder, ColoradoSeptember 23, 2004
Presentation Overview
General overview of lab QA/QC
Sampling considerations Facility considerations Method 1631 QA/QC
requirements PT requirments Summary
Basic QA/QC Approach
Ref: John Taylor, “Quality Assurance of Chemical Measurements” Lewis Publishers, 1987
Artisan Based on expertise of person completing the task
Academic researchChef Good approach in a non-regulatory situationSmall one, two person laboratories
Basic QA/QC Approach
SystematicDependent on Quality SystemIndependent of person performing taskCook book approach Documentation – lots of itResults can be reviewedUsually required in regulatory situation
Sampling considerations
EPA Method 1669 Can’t be emphasized enough
“The ease of contaminating ambient water samples…cannot be overemphasized.” – Section 1.4
Sample bottles from commercial vendor or produced per Section 6.1.2
Sample bottle considerations
Example: ESSGlass (Hg only) or Teflon containers washed per the method with detergent, trace grade nitric acid and Milli Q DI rinsing with drying in a “Low Particle” oven.
Bottles available with preservation; HCl or Bromine monochloride.
Analyze these containers by lot by method 1631 to <0.15 ng/L. The analytical report is provided with the containers.
Bottles double bagged.
Containers
Lab considerations
Ref: Hampton Roads Sanitation District – Virginia Beach, Virginia
Use a dedicated roomDoesn’t have to be a clean roomSimply dedicated to low level Hg
Use a Class 100 clean bench to produce reagents, standards and samples
Bake KBrO3 for 8 hours at 250oC prior to using it to produce bromine monochloride solution
Lab considerations
Disposable tubes on autosamplerRinsed with high purity water
Glassware washingSoak in 1:1 nitric for at least 24 hoursRinse with high purity waterUse immediately
Bubble argon though stannous chloride for 30 minutes prior to startingContinue to bubble argon through stannous chloride during analysis
Method 1631 QA/QC
Contamination ControlSection 4.3
InterferencesSection 4.4
Reagents and StandardsSection 7.0
Sample Collection, Preservation and StorageSection 8.0
Section 9.0 QC Changes to method – Section
9.1.2“9.1.2 In recognition of advances…the analyst is permitted certain options to improve results or lower the cost of measurements. These options include automation of the dual-amalgamation system, single-trap amalgamation (Reference 14), direct electronic data acquisition, calibration using gas-phase elemental Hg standards, changes in the bubbler design (including substitution of a flow-injection system) to maximize throughput, or changes in the detector (i.e., CVAAS), where less sensitivity is acceptable or desired. Changes in the principle of the determinative technique, such as the use of colorimetry, are not allowed. If an analytical technique other than the CVAFS technique specified in this method is used, that technique must have a specificity for mercury equal to or better than the specificity of the technique in this method.”
Method 1631
QC by batch 1 – 20 samplesSame 12 hour shift
Method 1631
Batch – Section 9.1.7Three blanksFive calibration standardsOngoing precision and recovery (OPR)Quality control sampleMethod blankSeven samples
Method 1631
Batch (continued)Method blankThree samplesMatrix spike/Matrix spike duplicateFour samplesMethod blankSix samplesMatrix spike/Matrix spike duplicateOngoing Precision and Recovery
Method 1631
Initial Demonstration of Capability - Section 9.2Method Detection Limit – equal to or less than 0.5 ng/L (Section 9.2.1)Initial precision and recovery (Section 9.2.2)79 – 121% (Accuracy)21% RSD (Precision)Four replicates
Method 1631
Matrix Spike/Matrix Spike Duplicate – Section 9.3Spike at 1-5 times the sample concentration71 – 125 % (accuracy)24% RSD (precision)
Method 1631
Blanks – Section 9.4Bubbler blanksSystem blanksReagent blanksMethod blanksField blanksEquipment blanksBottle blanks
Method 1631
Ongoing precision and recovery (Section 9.5)77 – 123% (Accuracy)Same source as that used for calibrationICV/CCV
Method 1631
Quality control sample (Section 9.6)No limits specified in method
Suggestion is to use OPR limitsDifferent source than that used for calibration, external to lab or made internally from second sourceWibby Environmental
QC-UTM-WP, $95QC-UHG-WP, $65
Method 1631
Field duplicates (Section 9.7)May be required to meet project specific requirements
Method 1631
Calibration (Section 10)Very specific requirements that must be metShould review and be familiar with requirements
PT Requirements
Necessary for accreditation Once a year or twice a year Levels much higher than trace levels
0.5 – 30 ug/L (WP)0.5 – 10 ug/L (WS) Method 1631 0.005 – 0.100 ug/L
Acceptance criteria differentApproximately + 24% (WP)+ 30% (WS)
Thank You!
Chuck WibbyWibby Environmental
6390 Joyce Drive, #100
Golden, CO 80403303-940-0033