Detect Limits as Representation for a Standard

VAP Rule DiscussionDawn Busalacchi

Risk Assessor, DERR, Central Office

Purpose of Discussion

• Address section of the rule which provides use of an appropriate detection limit as representation for an applicable standard

• Clarify language as it pertains to lab practice vs. Ohio EPA VAP Rule

• Discuss applicable portions of rule• Discuss uncertainties (intention) of rule • Set out what Ohio EPA expectations are• Cover basic CP responsibilities regarding this issue• Provide options for CPs • Enumerate some specific scenarios

Acronyms• Roughly Equivalent:– LoD = Limit of Detection– DL – Detect Limit– MDL = Method Detect Limit

• Roughly Equivalent:– LoQ = Limit of Quantitation– RL = Reporting Limit– PQL = Practical Quantification Level

Definitions...

Limit of Detection (LoD)

• Detection of a signal by lab instrument approximately 3 standard deviations above background blank signal (also known as noise)

• Established through a lab “study” – typically using 2 instruments to analyze multiple replications of a “spiked” blank to establish

Method Detect Limit (MDL)

• The minimum concentration that can be detected (“seen”) by an instrument for a SPECIFIC method with some degree of confidence (typically 95 - 99% )

• Similar to but not exactly the same as an LoD

MDL – US EPA

• The MDL procedure sets the limit of detection at the 99% confidence level, according the U.S. Environmental Protection Agency's (EPA) MDL procedure promulgated at 40 CFR (Code of Federal Regulations) Part 136, Appendix B, rev. 1.11.

• The EPA defines the MDL as the "minimum concentration of substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero, and is determined from analysis of a sample in a given matrix containing the analyte".

RL AKA LoQ AKA PQL

• Lowest level that can be reliably achieved during routine laboratory operating conditions. The PQL is approximately 2 – 5 X calculated MDL. (Vermont Department of Environmental Conservation)

• Lowest concentration where 95% confidence interval is within 20% of true concentration of sample (determined by standards testing). Percent uncertainty at the 95% confidence level shall not exceed 20% of the results for concentrations greater than the PQL. (United States Department of Energy)

• 3x lowest point on the calibration curve (common practice with commercial labs)

What Terms Do Ohio EPA VAP Rules Use?

• Analytically, these terms are different but...

• For the purposes of this rule discussion today, we will use what is detected vs. what is quantified... interchangeably

Blank → Detect → Quantify

VAP Applicable Rules • OAC 3745-300-04 Certified Laboratories (CL): – (H)(7) – Lab must disclose when it cannot quantify standard

using a method it is certified for• OAC 3745-300-07 Phase II:– (D)(2)(b) – Volunteer (CP) must ensure CL certified and

capable of performing analyses required– (D)(2)(c) – Volunteer (CP) must communicate standards

required to the CL, which must disclose when it is not CAPABLE of detecting [COCs] at or below applicable standard...An appropriate detection limit may be used to represent any applicable standard where the CL is not capable of detecting COCs at or below the applicable standard until such time that a lower detection is achieved

What does this mean?• Volunteer (CP) must communicate standards...

– How?– To Whom?

• CL must disclose when not capable of detecting...– How?

• DL may be used to represent applicable standard...– Why?– When?

• Until such time that a lower DL is achieved...– Then what? – How is this documented?

• Discussion...

Rule Requirements

• CP must communicate to CL what VAP standards are

• CL must communicate to CP what MDL they are able to meet, and IF THEY ARE UNABLE TO MEET ANY OF THE VAP STANDARDS

• CP must ALSO communicate this to Ohio EPA• This must be documented in NFA Executive

Summary and Phase II

How can DLs be lowered?

• Labs have many ways to achieve lower DLs:– Optimize method, such as increase run time,

increase purge volumes– Utilize Selective Ionization Mode (SIM) – Utilize Isotopic Analysis – Test for select analytes instead of whole suite– Use another method with lower DLs

What if Lab Can’t?

• CP has choice to go to another CL – instruments and capabilities vary from lab to lab

• Place an institutional control on property to limit pathway

• Utilize rule 3745-300-07(D)(2)(c)

Potential Scenario • There is a source area of COC XYZ on the property• My lab cannot detect COC XYZ down to the

concentration of the standard: • Now what?

– Did you communicate VAP standards to CL?– Did CL inform you of their limitations?– Did you advise CL to optimize methods or use another one?– Did you consider going to another CL?– Did you summarize your efforts in section 4.0, and detail

final standard in Table 4.1, Part E, Executive Summary of the NFA Letter, and in detail in the phase II?

Hypothetical Example

• Benzidine in soil: – Source area on property– Proposed use of property is residential– GDCSS (residential standard) = 0.042 mg/kg– CL’s MDL = 0.10 mg/kg– CL’s PQL = 0.30 mg/kg– CL’s RL = 0.30 mg/kg

• So what the CL will actually report is no lower than 0.3 mg/kg

Standard = 0.042

MDL = 0.10

PQL = 0.30

mg/kg

Chromatogram of Benzidine Concentrations

Above Standard

Below Standard

Direct Contact Soil Standard vs. MDL

Time

Implications

• Important to realize that if RL accepted as standard...– Actual COC concentration could be either:– Below MDL and below standard or – Below MDL and above standard

• Likely that any standard can be reached depending on lab capabilities and method chosen

• Should RL become achievable in future, demonstration with standard may be required

Questions

• 1. My lab is VAP certified for US EPA Method XYZ. Are they automatically certified for Selective Ionization Mode (SIM) within this method?– NO – the SIM must have an SOP that was reviewed

and accepted when the lab was certified for the Method

• 2. Even after optimization, my lab cannot reach the standard. Do I need to go to another lab?– That depends...CP should carefully consider on and

off site receptors, toxicity of COC and cumulative summary of all COCs

Questions and Discussion

http://www.xula.edu/prem/images/facil/large/Agilent%206890%20Gas%20Chromatography%20with%20Mass%20Spectrometer%20(GC-MS%20)(2).jpg

• Acknowledgements:

– Thanks to Mike Allen, Martin Smith, Audrey Rush and Darlene Stanley for their assistance with this presentation

• Sources:

– Ohio EPA VAP Rules August 2014– US EPA 40 CFR Part 136 Appendix B, rev.1.11– www.ncbi.nim.nih– http://

www.mywaterquality.ca.gov/monitoring_council/collaboration_network/docs/bvanbuuren_jan2012.pdf

THANK YOU!