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Paul Armishaw
Manager, Chemical Reference Values
National Measurement Institute Australia

Per- and poly- fluoroalkyl substances (PFAS) are a group of chemicals that have been widely used in industry since the 1950s. PFAS include chemicals such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA, Figure 1). PFAS have been used in the manufacture of non-stick cookware, fabric, furniture and carpet stain protection applications, food packaging, some industrial processes and in fire-fighting foam. Many PFAS can persist in humans, animals and the environment. Although there is currently no consistent evidence that exposure to PFAS causes adverse human health effects, experts recommend that exposure to PFAS is minimised as a precaution.



Figure 1 Linear PFOS and PFOA.

In recent years, testing and monitoring of PFAS in Australia has increased in response to environmental contamination associated with previous use of PFAS-containing fire-fighting foams. Measurement of PFAS in environmental or biological samples is typically performed using HPLC coupled with tandem MS and incorporating isotopically labelled internal standards. PFAS are present in the environment as mixtures of linear and branched isomers, together with numerous precursor chemicals and degradation products; appropriate calibration standards are not available for all of these compounds, so measuring low levels of this mixture of fluorinated chemicals in the environment is not a trivial task.

Proficiency testing (PT) is an important part of laboratory quality assurance, providing an independent means of demonstrating the accuracy of results. PT is also a useful educational tool, allowing participant laboratories to learn from their peers. Finally, participation in PT is a requirement for accreditation to the ISO 17025 standard. In 2015, in conjunction with CRC CARE, NMI established a proficiency testing PFAS chemicals in soil, water and biota. Since then, interest in the program from Australian and overseas testing laboratories has grown; three rounds of PT have been conducted (Figure 2), with successive rounds including additional matrices and analytes. NMI also had the PFAS PT scheme added to the scope of our ISO17043 accreditation as a PT provider.

2015

PFOS


PFOA

 


Soil
Water

2016

PFOS


PFOA

 



Soil
Water
Fish

 

2017

PFOS
PFOA
PFHxS
FOSA
PFBA
PFPeA
PFHpA

PFHxA
PFNA
PFDA
PFBS
6:2FTS
8:2FTS



Soil
Water
Fish

 



 

Figure 2 The NMI PFAS PT Program.

The test samples have included soil, water and fish tissue and levels of PFAS were chosen to reflect those relevant to environmental assessment. Samples were taken from contaminated sites and had incurred levels of PFAS, or were prepared (spiked) by NMI. Soil samples were ground and sieved; fish samples were ground after embrittlement with liquid nitrogen (Figure 3). Over the course of each PT round, the homogeneity and stability of the samples was assessed. Participating laboratories were asked to use their normal test methods and to report a single result for each analyte, together with its expanded uncertainty. Figure 4 shows results for PFOS in spiked soil from the 2016 PT round.

The performance of laboratories, in terms of satisfactory scores, was similar to or better than that in other NMI PTs of environmental measurements such as pesticides. In the 2016 round, 92% of results returned a satisfactory z-score, an excellent outcome, considering the difficulties associated with measuring trace levels of these complex analytes in environmental and biological matrices.

Following the 2015 and 2016 rounds of PT, NMI facilitated stakeholder workshops. These workshops were attended by laboratory staff, regulators such as state EPAs, and environmental remediation professionals. Results of the PT, plans for future rounds and issues related to PFAS contamination were discussed. Feedback from attendees was positive, and showed the strong stakeholder interest in having good quality measurement data upon which to base environmental assessment.

NMI plans to continue offering PT of PFAS compounds, with additional matrices and compounds added in response to stakeholder needs. Remaining test samples from these PTs are also useful for method validation or quality control. Further information on the NMI PT program, including reports of the PFAS PTs, can be found on the NMI website.



Figure 3 Homogenising a PFAS-containing fish sample embrittled with liquid nitrogen.



Md = median, R.A. = robust average, HV = NMI homogeneity testing, S = spike.
Figure 4 Proficiency test results for PFOS in Soil. (AQA 16-06, November 2016)

NMI Training Dates
NMI offers a range of specialised training courses. Upcoming dates are listed below or for further information, take a look at the training page on their website

Date

Training

Location

Price (ex. GST)

1 November

Verifying non-automatic weighing instruments

Brisbane

$679

8 November

Verifying fuel dispensers

Brisbane

$679

9 November

Weighbridge operators

Brisbane

$679

15 November

Introduction to estimating measurement uncertainty

Perth

$1,192

21 November

Verifying weighbridges

Sydney

$865

22 November

Verifying belt weighers

Sydney

$865

22/11

Estimating measurement uncertainty for biologists

Perth

$1,192

29/11

Introduction to estimating measurement uncertainty

Melbourne

$1,192

7/12

Introduction to estimating measurement uncertainty

Sydney

$1,192