Lab Manager | Run Your Lab Like a Business
Shot of a young woman transferring liquid from a pipette to a test tube in a laboratory

Effective Proficiency Testing Helps Reduce Lab Compliance Errors

Advice on how to set up and execute proficiency testing

Scott D. Hanton, PhD

Scott Hanton is the editorial director of Lab Manager. He spent 30 years as a research chemist, lab manager, and business leader at Air Products and Intertek. He earned...

ViewFull Profile.
Learn about ourEditorial Policies.
Register for free to listen to this article
Listen with Speechify

Maintaining compliance with lab-specific procedures and regulatory requirement standards is important to delivering high quality technical results. Failure to comply can result in incorrect results, environmental contamination, fines, or even criminal penalties. 

Richard Jack, PhD, the global market development manager of food and environmental for Phenomenex, shares his advice on how to avoid common lab compliance errors. Jack has over two decades of experience, including developing relationships and collaborating with global regulatory agencies to assist in validated methods. He is also an expert in the new EPA analytical methods 1633 (for PFAS) and 1621 (for adsorbable organic fluorine).

Get training in Lab Quality and earn CEUs.One of over 25 IACET-accredited courses in the Academy.
Lab Quality Course

Q: Can you explain the steps laboratories take to ensure they are following proficiency testing procedures accurately? 

A: Proficiency testing involves the analysis of a sample sent to a laboratory from a third party.  In most cases, the lab uses a validated method and must meet various parameters to demonstrate that they are performing the method accurately. Once this is accomplished, a lab wants to perform compliance monitoring. They also analyze a proficiency test (PT) sample. The PT is an unknown, and the lab must determine the concentration of analytes in the PT and report the results to the third-party agency. If the results are within certain specific parameters, then they pass. 

Q: What measures are in place to prevent common compliance errors during proficiency testing?

A: For many environmental labs, they have two opportunities to pass the PT sample. The measures in place are usually built within a method, such as blanks, system suitability, matrix spikes and spike duplicates, and continuous calibration. For example, a lab spikes a sample and measures the true value from the predicted value based on the spiked amount. This gives them confidence that they can measure a potential unknown. They can also buy various QC samples and standards from the third party before they participate in the actual PT study. 

Q: What processes are in place for laboratories to identify and rectify compliance errors detected during proficiency testing? 

A: There are several options. The first step is to ensure they meet method criteria and internal system suitability, and continuous calibration checks over the course of the batch of samples. For example, every 10 samples, labs then analyze calibration check samples and known samples to make sure the instrument is working properly. 

Q: Can you provide examples of corrective actions laboratories commonly take to address errors in proficiency testing? 

A: It’s really a methodical process of doing precise lab work in conjunction with careful documentation. Labs must first determine the root cause of their error. This may begin with reviewing the sample preparation steps, checking dilution volumes, preservation, etc. 

  • Reporting errors: transcription of results, erroneous reporting of results. Were dilutions properly recorded or out of the calibration range?
  • For Identification: Was the analysis performed correctly? Were baseline noise and drift within acceptable limits? Was the system reporting the same values over the course of a day or between days using the same control samples? Were the method detection limits and reporting limits acceptable for the method and consistent over time?
  • Did the analyst calculate correctly? 
  • Can they verify the initial and continual calibration checks, blanks, lab control samples, secondary QC samples, surrogates, and internal standards were reported accurately?

These are just some examples of what labs can do to make sure they are performing accurate analysis before they run the PT, but also if they fail.

Q: What measures are taken to ensure laboratory staff are adequately trained to minimize compliance errors during proficiency testing? 

A: Most labs have standard operating procedures that deal with personnel training. These can vary depending on the instrument and analysis they are performing and skill level. In most cases, the senior lab manager or QC director is responsible for making sure personnel are trained and certified on a regular basis. The measures taken vary, but in general involve internal unknowns or share samples between groups and or between laboratories and compare results. 

Q: What additional challenges do laboratories face when dealing with specific proficiency test samples, such as those containing PFAS compounds? 

A: The PT difficulties are really the same as any sample, since the concentration of analytes are unknown in both cases. One advantage of the PT is that it’s probably cleaner and has less matrix effects than the actual samples. The steps are the same as described above.

Q: How do laboratories ensure accuracy and compliance when analyzing PFAS compounds in proficiency testing samples, given their variability and specific EPA regulations? 

A: The PT process itself is not very different than any other PT process. However, PFAS compounds are unique in that they are prevalent in many materials, solvents, used LC components, clothing, personal care products, and they can show up in blanks and also provide background problems—Not just for the PT, but analyses in general. 

Q: Can you provide more insights on EPA Method 1633? 

A: EPA 1633 has very specific requirements, which may seem laborious, but help ensure that the final results have no issues throughout the entire workflow to meet the rigors of compliance monitoring. These include, but not limited to:

  • Ensure the system calibration and stability are in place
  • Ensure there is little to no interference from any PFAS background (clean instrument and method blanks)
  • Reduce matrix effects from sample collection, sample preservation, sample preparation, analysis, and little contribution from instrument drift.  

Here is a draft EPA Method 1633. Nine injections are made prior to injection of the first sample extract! Notice that calibration verification and blanks are required between each batch of 10 samples.

After a successful initial calibration has been completed, the analytical sequence for a batch of samples analyzed during the same time period is as follows. The volume injected for samples and QC samples must be identical to the volume used for calibration (Section 10.2.3). Standards and sample extracts must be brought to room temperature and vortexed prior to aliquoting into an instrument vial in order to ensure homogeneity of the extract.

1. Instrument Blank 

2. Instrument Sensitivity Check (see Section 7.3.4) 

3. Calibration Verification Standard 

4. Qualitative Identification Standards 

5. Instrument Blank 

6. Method Blank 

7. Low-level OPR (LLOPR) Low level ongoing precision and recovery

8. OPR (ongoing precision and recovery)

9. Bile salt interference check standard (Section 7.5) 

10. Injections of sample extracts, diluted extracts, and QC sample extracts (10 or fewer field sample extracts) 

11. Calibration Verification Standard 

12. Instrument Blank 

13. Injections (10 or fewer field sample extracts) 

14. Calibration Verification Standard 

15. Instrument Blank 

If the results are acceptable, the closing calibration verification solution (#14 above) may be used as the opening solution for the next analytical sequence.  

Q: How can lab managers develop a culture of compliance?

A: To build a culture of compliance in the company or lab:

  • Ensure proper training 
  • Develop and use standard operating procedures (SOP)
  • Document procedures and sections within the SOP:
    1. Require the manager co-sign that steps are met during the compliance process. 
    2. Have a second person read the steps, checks, or any modifications so that they are understood.
  • Complete compliance audits by consultants or someone outside the lab
  • Use compliance to generate business value. Tell customers they pass audits and meet ISO compliance