Interlaboratory Proficiency Test 18/2020. PAH measurements from indoor air samples

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Finnish Environment Institute

INTERLABORATORY PROFICIENCY TEST 18/2020

ISBN 978-952-11-5173-6 (pbk.) ISBN 978-952-11-5174-3 (PDF) ISSN 1796-1718 (print) ISSN 1796-1726 (Online)

FINNISH ENVIRONMENT INSTITUTE

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Interlaboratory Proficiency Test 18/2020

PAH measurements form indoor air samples Mirja Leivuori, Evgeny Parshintsev,

Outi Kammonen, Riitta Koivikko, Keijo Tervonen, Sari Lanteri and Markku Ilmakunnas

REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 22 | 2020

SYKE

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Helsinki 2020

Finnish Environment Institute

REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 22 | 2020

Interlaboratory Proficiency Test 18/2020

PAH measurements from indoor air samples

Mirja Leivuori¹, Evgeny Parshintsev²,

Outi Kammonen², Riitta Koivikko¹, Keijo Tervonen¹, Sari Lanteri¹ and Markku Ilmakunnas¹

1 Finnish Environment Institute (SYKE), Laboratory Centre, Helsinki, Finland

2 Finnish Institute of Occupational Health (FIOH) Helsinki, Finland

SYKE

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REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 22 | 2020 Finnish Environment Institute SYKE

Proftest SYKE

Layout: Markku Ilmakunnas

The publication is also available in the Internet: www.syke.fi/publication | helda.helsinki.fi/syke

ISBN 978-952-11-5173-6 (pbk.) ISBN 978-952-11-5174-3 (PDF) ISSN 1796-1718 (print) ISSN 1796-1726 (Online)

Author(s): Mirja Leivuori, Evgeny Parshintsev, Outi Kammonen, Riitta Koivikko, Keijo Tervonen, Sari Lanteri and Markku Ilmakunnas

Publisher and financier of publication: Finnish Environment Institute (SYKE) Latokartanonkaari 11, FI-00790 Helsinki, Finland, Phone +358 295 251 000, syke.fi.

Year of issue: 2020

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ABS TR ACT • TIIVISTELM Ä • SAMM ANDRAG Interlaboratory comparison 18/2020

Proftest SYKE organized in cooperation with Finnish Institute of Occupational Health (FIOH) an interlaboratory comparison (ILC) for the analysis of PAH compounds of the indoor air collected into XAD adsorbent tubes (Orbo 43) in March 2020 (IAPAH 18/2020). The measurements of anthracene, acenaphthene, acenaphthylene, fluoranthene, fluorene, 1-metylnaphthalene, 2-metylnaphthalene, naphthalene, phenanthrene, and pyrene were tested from the synthetic sample.In total five participants took part in the comparison. The calculated values were used as the assigned values for the results of the synthetic samples. The performance evaluation was based on the z scores. In total 68 % of the results reported by the participants were satisfactory when deviation of 20–30 % from the assigned value was accepted.

Warm thanks to all the participants of this interlaboratory comparison!

Keywords: interlaboratory comparison, PAH compounds, indoor air, synthetic sample

TIIVI S TELM Ä

Laboratorioiden välinen vertailumittaus 18/2020

Proftest SYKE järjesti yhteistyössä Työterveyslaitoksen (TTL) kanssa vertailumittauksen laboratorioille, jotka tekevät sisäilmanäytteiden PAH-yhdisteiden määrityksiä XAD-adsorbenttiputkista (Orbo 43) maaliskuussa 2020 (IAPAH 18/2020). Vertailumittauksessa testattiin synteettisten näytteiden antraseeni, asenafteeni, asenaftyleeni, fenatreeni, fluoranteeni, fluoreeni, 1-metyylinaftaleeni, 2-metyylinaftaleeni, naftaleeni ja pyreeni määritysten vertailtavuutta. Vertailumittaukseen osallistui yhteensä 5 laboratoriota. Laskennallista pitoisuutta käytettiin vertailuarvona synteettisten näytteiden raportoiduille tuloksille. Tulosten arviointi tehtiin z-arvoilla. Koko tulosaineistossa hyväksyttäviä tuloksia oli 68 %, kun vertailuarvosta sallittiin 20–30 % poikkeama 95 % luottamusvälillä.

Kiitos vertailumittauksen osallistujille!

Avainsanat: vertailumittaus, PAH-yhdisteet, synteettinen näyte, sisäilma

S AMM ANDR AG Interkalibrering 18/2020

Proftest SYKE genomförde tillsammans med Arbetshälsoinstitutet (TTL) i mars 2020 en interkalibrering (IAPAH 18/20) av omfattade bestämningen av XAD-adsorberande rör (Orbo 43) som används för inomhus PAH mätningar. I interkalibrering testades analyserna jämförbarheten halten av antracen, acenaftalen, acenaftylen, fenatren, fluoranten, fluoren, 1-metylnaftalen, 2-metylnaftalen, naftalen och pyren från syntetiska provernas. Totalt 5 deltagare deltog i interkalibreringen. Som referensvärde för de syntetiska provernas ämnesspecifika resultat användes beräkningskoncentratio- nerna. Resultaten värderades med hjälp av z värden. I interkalibrering var 68 % av alla resultaten acceptabla, när en total deviation på 20–30 % från referensvärdet tilläts.

Ett varmt tack till alla deltagarna i testet!

Nyckelord: interkalibrering, PAH ämnes, syntetiskt prov, inomhusluft

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Proftest SYKE IAPAH 18/20 5

CONTENTS

Abstract • Tiivistelmä • Sammandrag ... 3

1 Introduction ... 7

2 Organizing the proficiency test ... 7

2.1 Responsibilities ... 7

2.2 Participants ... 8

2.3 Samples and delivery ... 8

2.4 Homogeneity and stability studies ... 8

2.5 Feedback from the proficiency test ... 9

2.6 Processing the data ... 9

2.6.1 Pretesting the data ... 9

2.6.2 Assigned values ... 9

2.6.3 Proficiency assessment procedure ... 9

3 Results and conclusions ... 10

3.1 Results ... 10

3.2 Analytical methods ... 11

3.2.1 Backround survey of the used analytical methods ... 11

3.3 Uncertainties of the results ... 11

4 Evaluation of the results ... 12

5 Summary ... 13

6 Summary in Finnish ... 13

References ... 14

: Participants in the proficiency test ... 15

: Sample preparation ... 16

: Homogeneity of the samples ... 17

: Stability of the samples ... 18

: Feedback from the proficiency test ... 19

: Evaluation of the assigned values and their uncertainties ... 20

: Terms in the results tables ... 21

: Results of each participant ... 22

: Results of participants and their uncertainties ... 25

: Summary of the z scores ... 32

: z scores in ascending order ... 33

: Background survey of analytical methods ... 40

: Results grouped according to the methods ... 41

: Examples of measurement uncertainties reported by the participants ... 48

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6 Proftest SYKE IAPAH 18/20

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1 Introduction

Proftest SYKE organized in cooperation with Finnish Institute of Occupational Health (FIOH) an interlaboratory comparison (ILC) for the analysis of PAH compounds of the indoor air collected into XAD adsorbent tubes (Orbo 43) in March 2020 (IAPAH 18/2020). The measurements of anthracene (CAS No 120-12-7), acenaphthene (CAS No 83-32-9), acenaphthylene (CAS No 208-96-8), fluoranthene (CAS No 206-44-0), fluorene (CAS No 86-73-7), 1-metylnaphthalene (CAS No 90-12-0), 2-metylnaphthalene (CAS No 91-57-6), naphthalene (CAS No 91-20-3), phenanthrene (CAS No 85-01-8), and pyrene (CAS No 129-00-0)were tested from the synthetic sample.

Finnish Environment Institute (SYKE) is appointed National Reference Laboratory in the environmental sector in Finland. The duties of the reference laboratory include providing interlaboratory proficiency tests and other comparisons for analytical laboratories and other producers of environmental information. This proficiency test has been carried out under the scope of the SYKE reference laboratory and it provides an external quality evaluation between laboratory results, and mutual comparability of analytical reliability. The proficiency test was carried out in accordance with the international standard ISO/IEC 17043 [1] and applying ISO 13528 [2] and IUPAC Technical report [3]. The Proftest SYKE is accredited by the Finnish Accreditation Service as a proficiency testing provider (PT01, ISO/IEC 17043, www.finas.fi/sites/en). The organizing of this interlaboratory comparison is not included in the accreditation scope of the Proftest SYKE, but the organizing follows the procedures of the accredited schemes.

2 Organizing the proficiency test

2.1 Responsibilities

Organizer

Proftest SYKE, Finnish Environment Institute (SYKE), Laboratory Centre Mustialankatu 3, FI-00790 Helsinki Finland

Phone: +358 295 251 000, Email: proftest@environment.fi

The responsibilities in organizing the interlabotory comparison Mirja Leivuori coordinator

Riitta Koivikko substitute for coordinator Keijo Tervonen technical assistance Markku Ilmakunnas technical assistance Sari Lanteri technical assistance Co-operation partner and analytical experts

Evgeny Parshintsev and Outi Kammonen, Finnish Institute of Occupational Health (FIOH, T013 accredited by FINAS, www.finas.fi/sites/en), firstname.lastname@ttl.fi

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Subcontracting:

Sample preparation and PAH measurements carried out by FIOH.

2.2 Participants

In total 5 laboratories participated in this interlaboratory comparison (Appendix 1), four from Finland and one from abroad. One participant reported two separate sets of results.

Four participants used accredited analytical methods for at least part of the measurements. The samples were prepared and tested at the laboratory of FIOH and their participant code is 3 in the result tables.

2.3 Samples and delivery

Participants received following samples:

o Blank sample (IA0PAH),

o Two synthetic samples (IA1PAH and IA2PAH), which were replicate samples, i.e.

prepared concurrently and similarly.

The synthetic samples were prepared volumetrically in the laboratory of the FIOH. The concentrations of measurands in the synthetic sample were set according to the recommendations for the maximum PAHs level in the indoor air described in the background note by FIOH [5].

The sample preparation is described in detail in the Appendix 2.

The samples were delivered on 16 March 2020 and they arrived to the participants at the latest on 18 March 2020. The samples were requested to be analyzed shortly after their arrival and latest on 20 February 2020.

Participants reported their results as requested latest on 25 March 2020. The preliminary results were delivered to the participants on 1 April 2020.

2.4 Homogeneity and stability studies

Homogeneity of the samples IA1PAH and IA2PAH was tested by measuring the all measurands from two to three subsamples (Appendix 3). According to the homogeneity test results, the samples were considered homogenous.

Stability of the samples IA1PAH and IA2PAH was tested by analysing the measurands from the samples stored at the room temperature until the informed last measuring date. The measurand values were checked against the results of the samples stored at 4 °C. All criteria were not fulfilled which indicates that the concentration could slightly decrease when samples are stored at 4 °C (Appendix 4). Nevertheless, in all the cases where the criterion was not fulfilled, the difference is within the analytical error. Therefore, the samples were considered stable enough (Appendix 4).

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During the interlaboratory comparison and in pretests before the round it was noticed, that the samples were more stable at room temperature than at 4 °C temperature within the period of one week. The test showed that the concentration of some PAHs slightly decreases at 4 °C temperature. However, during the second week it was noticed that the decrease in concentrations is similar in both temperatures. Thus, it is recommended to store the XAD adsorbent tube samples at the room temperature for one week at maximum. Also, it is highly recommended to extract the samples upon arrival to the laboratory, since sample extracts can be stored at 4 °C until analysis without loss of volatile PAHs for considerably longer time.

2.5 Feedback from the proficiency test

The feedback from the proficiency test is shown in Appendix 5. The comment from the participant is related to erroneously reported results. The comment from the provider is related to the lacking conversancy to the given information with the results. All the feedback from the proficiency test is valuable and is exploited when improving the activities.

2.6 Processing the data

2.6.1 Pretesting the data

To test the normality of the data the Kolmogorov-Smirnov test was applied. The outliers were rejected according to the Grubbs test before calculating the mean. The results, which differed from the data more than 50 % from the calculated value, were rejected before the statistical results handling

More information about the statistical handling of the data is available in the Guide for participant [5].

2.6.2 Assigned values

This ILC was provided for the first time and the number of reported results was low. Thus, the calculated values were used as the assigned values for the measurands. The expanded uncertainties of the assigned values were estimated using standard uncertainties associated with individual operations involved in the volumetric sample preparation [3]. The expanded uncertainties of the assigned values were between 4.6 % and 6.3 % (Appendix 6).

After reporting the preliminary results no changes have been done for the assigned values.

2.6.3 Proficiency assessment procedure

The standard deviation for proficiency assessment (spt) was estimated based on the measurand concentration, the results of homogeneity tests, the uncertainty of the assigned value, and the total measurement uncertainty of the expert laboratory. The results of this interlaboratory comparison were evaluated with the z scores (Appendix 2). The standard deviation for the

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proficiency assessment (2×spt, at the 95 % confidence level) was set to 20–30 % depending on the measurand.

After reporting the preliminary results no changes have been done for the standard deviations of the proficiency assessment values.

3 Results and conclusions

3.1 Results

The summary of the results of this interlaboratory comparison is presented in Table 1.

Explanations of the terms used in the result tables are presented in Appendix 7. The results and the performance of each participant are presented in Appendix 8. The reported results with their expanded uncertainties (k=2) are presented in Appendix 9. The summary of the z scores is shown in Appendix 10 and the z scores in the ascending order in Appendix 11.

Two replicate synthetic samples (IA1PAH and IA2PAH), i.e. prepared concurrently and similarly, were delivered to the participants. The results of the synthetic samples were processed separately, and the results were reported as compound responses. The standard deviation of the reported results varied from 8.5 to 44 % (Table 1).

Table 1. The summary of the results in the proficiency test IAPAH 18/2020.

Measurand Sample Unit Assigned value Mean Median s s % 2 x spt % nall Acc z %

Anthracene IA1PAH ng/sample 20.0 18.6 16.9 4.0 21.7 25 6 67

CAS No 120-12-7 IA2PAH ng/sample 20.0 16.6 17.8 3.4 20.7 25 6 67

Acenaphthene

CAS No 120-12-7

IA1PAH ng/sample 110 105 103 16 15.4 20 6 83

CAS No 83-32-9 IA2PAH ng/sample 110 92 92 21 22.9 20 6 50

Acenaphthylene IA1PAH ng/sample 210 194 201 16 8.5 20 6 83

Fluoranthene IA1PAH ng/sample 30.0 26.2 27.0 4.1 15.6 30 6 83

Fluorene IA1PAH ng/sample 30.0 28.8 29.0 4.4 15.2 20 6 83

1-Methylnaphthalene IA1PAH ng/sample 9.99 10.22 10.00 1.13 11.0 20 3 100

2-Methylnaphthalene IA1PAH ng/sample 10.0 10.6 10.8 1.3 12.6 20 3 100

Naphthalene IA1PAH ng/sample 110 114 118 24 21.3 20 6 50

Phenanthrene IA1PAH ng/sample 20.0 19.5 20.7 2.7 13.9 25 6 83

Pyrene IA1PAH ng/sample 20.0 17.6 18.0 3.1 17.6 25 6 67

s: the standard deviation, s %: the standard deviation as percent, 2×spt %: the standard deviation for proficiency assessment at the 95 % confidence level, nall: the total number of the participants, Acc z %: the results (%), where z  2.

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3.2 Analytical methods

The participants were allowed to use different analytical methods for the measurements in the ILC. A questionnaire related to the used analytical methods was provided along the interlaboratory comparison. The summary of the answers is shown in Appendix 12. The used analytical methods and the results of the participants grouped by methods are shown in more detail in Appendix 13.

3.2.1 Backround survey of the used analytical methods

In the background survey participants were asked to report some basic information of the used extraction and analytical methods (Appendix 12). Mainly the participants extracted the XAD adsorbent with dichloromethane, only one participant used toluene. Mainly the extraction was done by sonication, while one participant used shaking (Appendix 12). Based on the answers it could be concluded that the sonication is more efficient extraction method. If shaking is used instead, longer extraction time can be recommended.

The used analytical methods of the participants and results are shown in more detail in Appendix 13. All participants used GC-MS techniques with some modifications.

3.3 Uncertainties of the results

All participants but one reported the expanded measurement uncertainties (k=2) with their results (Table 4, Appendix 14).

Several approaches were used to estimate the measurement uncertainty (Appendix 14). The most used approach was based on method validation data and IQC data from synthetic sample and/or CRM. Two participants used modelling approach for some measurands. For the estimation of uncertainties, the MUkit measurement uncertainty software is available, but it was not used in the estimations [6]. The free software is available in the webpage: www.syke.fi/envical/en.

Generally, the used approach to estimate the measurement uncertainty did not make definite impact on the uncertainty estimates.

The estimated uncertainties varied for the tested measurands and samples (Table 2). Within the optimal measuring range, the expanded measurement uncertainty (k=2) should be typically 20-40 %. Close to the limit of quantification the relative measurement is higher. When reporting measurement uncertainties, the accuracy of the numeric values should correlate with the accuracy of the result. It is evident that harmonization is still needed for the estimation of the expanded measurement uncertainties.

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Table 2. The range of the reported expanded measurement uncertainties (k=2, Ui%).

4 Evaluation of the results

The performance evaluation of the participants was based on the z scores, which were calculated using the assigned values and the standard deviation for proficiency assessment (Appendix 7).

The z scores were interpreted as follows:

Criteria Criteria

Performance Performance

 z   2 Satisfactory

2 <  z  < 3 Questionable

| z   3 Unsatisfactory

In total, 68 % of the results evaluated based on z scores were satisfactory when accepted deviation from the assigned value was 20–30 % at the 95 % confidence level (Appendix 10). Four participants used the accredited methods for at least some of the measurands and 59 % of those results were satisfactory. One participant informed their results as non-accredited and 91 % of those were satisfactory.

The summary of the performance evaluation is shown in Table 3. The percentage of the satisfactory results varied between 55 % and 80 % for the tested samples. The samples were replicate synthetic samples (IA1PAH and IA2PAH) which were prepared concurrently and similarly.

Table 3. Summary of the performance evaluation in the interlaboratory comparison IAPAH 18/2020.

Measurand Ui%, IA1PAH, IA2PAH

Acenaphthene 20-30

Acenaphthylene 20-32

Anthracene 20-32

Fluoranthene 30-32

Fluorene 20-30

1-Metylnaphthalene 20-30

2-Metylnaphthalene 20-30

Naphthalene 20-35

Phenanthrene 20-32

Pyrene 30-39

Sample Satisfactory results (%)

Accepted deviation from the assigned

value at 95 % confidence level (%)

Remarks

IA1PAH 80 20–30 • Difficulties in measurements for some of the

participants; satisfactory results < 80 % for anthracene, naphtalene, pyrene

IA2PAH 55 20–30 • Difficulties in measurements for all measurands;

satisfactory results < 80

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Recommendations:

• It is recommended to store the XAD adsorbent tubes at the room temperature at maximum one week. The extraction is recommended as soon as possible within one week after the sample collection. After extraction the effluent can store at 4 °C until the analysis.

• Sonication assisted extraction is recommended. If other techniques are used, attention must be paid on extraction time.

5 Summary

Proftest SYKE organized in cooperation with Finnish Institute of Occupational Health (FIOH) an interlaboratory comparison (ILC) for the analysis of PAH compounds of the indoor air collected into XAD adsorbent tubes (Orbo 43) in March 2020 (IAPAH 18/2020). The measurements of anthracene, acenaphthene, acenaphthylene, fluoranthene, fluorene, 1-metylnaphthalene, 2-metylnaphthalene, naphthalene, phenanthrene, and pyrene were tested from two synthetic samples. In total five participants took part in the interlaboratory comparison.

The calculated value was used as the assigned value for the measurands of the samples and the expanded uncertainties of the assigned values were between 4.6 % and 6.3 %.

The evaluation of the performance was based on the z scores. In this interlaboratory comparison 68 % of the data was regarded to be satisfactory when the result was accepted to deviate from the assigned value from 20 to 30 % at 95 % confidence level.

6 Summary in Finnish

Proftest SYKE järjesti yhteistyössä Työterveyslaitoksen (TTL) kanssa vertailumittauksen laboratorioille, jotka tekevät sisäilmanäytteiden PAH-yhdisteiden määrityksiä XAD- adsorbenttiputkista (Orbo 43) maaliskuussa 2020 (IAPAH 18/2020). Vertailumittauksessa testattiin antraseeni, asenafteeni, asenaftyleeni, fenatreeni, fluoranteeni, fluoreeni, 1-metyylinaftaleeni, 2-metyylinaftaleeni, naftaleeni ja pyreeni määritysten vertailtavuutta kahdesta synteettisestä näytteestä. Vertailumittaukseen osallistui yhteensä 5 laboratoriota.

Vertailuarvona kaikille testisuureille ja näytteille käytettiin laskennallista pitoisuutta.

Vertailuarvon laajennettu epävarmuus vaihteli välillä 4,6 –6,3 %.

Osallistujien pätevyyden arviointi tehtiin z-arvojen avulla. Koko tulosaineistossa hyväksyttäviä tuloksia oli 68 %, kun vertailuarvosta sallittiin 20–30 % poikkeama 95 % luottamusvälillä.

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REF ERENCE S

1. SFS-EN ISO 17043, 2010. Conformity assessment – General requirements for Proficiency Testing.

2. ISO 13528, 2015. Statistical methods for use in proficiency testing by interlaboratory comparisons.

3. Thompson, M., Ellison, S. L. R., Wood, R., 2006. The International Harmonized Protocol for the Proficiency Testing of Analytical Chemistry laboratories (IUPAC Technical report). Pure Appl. Chem. 78: 145-196, www.iupac.org.

4. Työterveyslaitos, 2010. PAH-yhdisteiden tavoitetasoperustelumuistio (päivitetty 2016).

https://www.ttl.fi/wp-content/uploads/2016/12/pah-yhdisteet-tavoitetaso.pdf (only in Finnish) 5. Proftest SYKE Guide for laboratories: www.syke.fi/proftest/en → Running proficiency test

https://www.syke.fi/download/noname/%7B3FFB2F05-9363-4208-9265-1E2CE936D48C%7D/39886.

6. Näykki, T., Virtanen, A. and Leito, I., 2012. Software support for the Nordtest method of measurement uncertainty evaluation. Accred. Qual. Assur. 17: 603-612. MUkit website:

www.syke.fi/envical.

7. Magnusson B., Näykki T., Hovind H., Krysell M., Sahlin E., 2017. Handbook for Calculation of Measurement Uncertainty in Environmental Laboratories. Nordtest Report TR 537 (ed. 4).

www.nordtest.info.

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APPENDIX 1 (1/1)

: Participants in the proficiency test

Country Participants

Finland Eurofins Environment Testing Finland Oy, Lahti Finnish Institute of Occupational Health

MetropoliLab Oy

Mikrobioni Oy

Sweden Eurofins Pegasuslab AB

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APPENDIX 2 (1/1)

: Sample preparation

The sample preparation was carried out in the laboratory of Finnish Institute of Occupational Health (FIOH). The used chemicals are shown in Table 1 and the final assigned value for the measurands in Table 2.

Table 1. The used chemicals for the synthetic samples IA1PAH and IA2PAH.

Producer, Producer code, Batch

Ehrenstorfer, ISO Guide 34 Reference material, PAH-Mix 61, G171686AM Ehrenstorfer, ISO 17034 Reference Material, PAH-Mix 14, G991633AL

Sample preparation:

The samples IA1PAH and IA2PAH were replicate synthetic samples, i.e. prepared concurrently and similarly. They were prepared volumetrically by pipetting 2 ml PAH-mix 14 and 200 µl PAH-mix 61 (Table 1) with dichloromethane into 10 ml volumetric bottle. From this mixture 5 µl was pipetted with Hamilton syringe into XAD adsorbent tubes (Orbo 43). The calculated assigned values are shown in Table 2.

Table 2. The assigned values of measurands in the samples IA1PAH and IA2 PAH.

Measurand Assigned value (ng/sample) (ng/sample)

Acenaphthene 110

Acenaphthylene 210

Anthracene 20.0

Fluoranthene 30.0

Fluorene 30.0

1-Metylnaphthalene 9.99

2-Metylnaphthalene 10.0

Naphthalene 110

Phenanthrene 20.0

Pyrene 20.0

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APPENDIX 3 (1/1)

: Homogeneity of the samples

Homogeneity was tested from duplicate measurements of selected measurement from two to three samples of each sample types (see table below).

Criteria for homogeneity

sa/sh<0.5 and ssam2<c, where

sh = standard deviation for testing of homogeneity

sa = analytical deviation, standard deviation of the results within sub samples

ssam = between-sample deviation, standard deviation of the results between sub samples c = F1 × sall2 + F2 × sa2, where

sall2 = (0.3 × sh)²

F1 and F2 are constants of F distribution derived from the standard statistical tables for the tested number of samples [2, 3].

Measurand/Sample Concentration

[ng/sample] n spt % sh% sh sanal sanal/sh sanal/sh<0.5? ssam2 c ssam2<c?

Anthracene/IA1PAH 18.5 3 12.5 9.1 1.68 0.65 0.39 Yes 2.57 2.59 Yes

Anthracene/IA2PAH 17.8 3 12.5 11.4 2.02 1.00 0.50 Yes 1.44 5.42 Yes

Acenaphthene/IA1PAH 200 2 10 3.5 7.00 2.25 0.32 Yes 60.9 61.2 Yes

Acenaphthene/IA2PAH 205 3 10 3.8 7.79 3.81 0.49 Yes 35.4 78.5 Yes

Acenaphthylene/IA1PAH 108 3 10 7.7 8.30 0.95 0.11 Yes 22.4 22.5 Yes

Acenaphthylene/IA2PAH 108 3 10 3.5 3.78 1.87 0.49 Yes 9.54 18.7 Yes

Fluoranthene/IA1PAH 28.1 2 15 4.8 1.35 0.38 0.28 Yes 1.91 1.91 Yes

Fluoranthene/IA2PAH 27.8 3 15 2.7 0.75 0.37 0.49 Yes 0.54 0.74 Yes

Fluorene/IA1PAH 29.5 2 10 5.0 1.47 0.60 0.40 Yes 0.96 3.87 Yes

Fluorene/IA2PAH 29.8 3 10 4.5 1.34 0.66 0.49 Yes 1.79 2.34 Yes

1-Metylnaphthalene/

IA1PAH

11.0 2 10 5.6 0.62 0.09 0.14 Yes 0.19 0.20 Yes

1-Metylnaphthalene/

IA2PAH

11.2 3 10 4.5 0.50 0.25 0.49 Yes 0.05 0.33 Yes

2-Metylnaphthalene/

IA1PAH

10.9 2 10 2.7 0.29 0.11 0.37 Yes 0.13 0.13 Yes

2-Metylnaphthalene/

IA2PAH

10.9 3 10 3.5 0.38 0.19 0.49 Yes 0.04 0.18 Yes

Naphthalene/IA1PAH 108 2 10 7.5 8.07 0.49 0.06 Yes 24.3 24.6 Yes

Naphthalene/IA2PAH 110 3 10 2.9 3.18 1.55 0.49 Yes 3.87 13.0 Yes

Phenanthrene/IA1PAH 19.0 2 12.5 3.1 0.59 0.29 0.49 Yes 0.42 0.85 Yes Phenanthrene/IA2PAH 18.9 3 12.5 8.3 1.57 0.30 0.19 Yes 1.04 1.05 Yes

Pyrene/IA1PAH 18.7 2 12.5 3.5 0.65 0.28 0.43 Yes 0.50 0.85 Yes

Pyrene/IA2PAH 18.7 3 12.5 4.9 0.92 0.45 0.50 Yes 0.19 1.11 Yes

Conclusion: The criteria were fulfilled. Thus, all the samples could be regarded as homogenous.

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APPENDIX 4 (1/1)

: Stability of the samples

The samples were delivered to the participants on 16 March 2020 and they arrived at the participants at the latest on 18 March 2020. The samples were requested to be analysed shortly after their arrival and latest on 20 March 2020.

The stability of the samples was tested by analysing two subsamples of the samples IA1PAH and IA2PAH stored at temperatures 4 °C and 20 °C.

Criterion for stability: D < 0.3 × spt, where

D = |the difference of the results of the samples stored at temperatures 4 °C and 20 °C|

spt = standard deviation for proficiency assessment

Measurand/Sample Assigned value

20.3.2020 20°C [ng/sample]

20.3.2020 4°C [ng/sample]

D 0.3 × spt D < 0.3 × spt ?

Anthracene/IA1PAH 20.0 14.6 14.0 0.54 0.75 Yes

Anthracene/IA2PAH 20.0 16.8 15.1 1.73¹ 0.75 No¹

Acenaphthene/IA1PAH 110 103.1 91.7 11.4¹ 3.30 No¹

Acenaphthene/IA2PAH 110 110.1 98.9 11.2¹ 3.30 No¹

Acenaphthylene/IA1PAH 210 191.4 173.1 18.3¹ 6.30 No¹

Acenaphthylene/IA2PAH 210 200.6 189.1 11.5¹ 6.30 No¹

Fluoranthene/IA1PAH 30.0 24.5 23.4 1.13 1.35 Yes

Fluoranthene/IA2PAH 30.0 26.8 23.7 3.18¹ 1.35 No¹

Fluorene/IA1PAH 30.0 27.1 24.6 2.51¹ 0.90 No¹

Fluorene/IA2PAH 30.0 39.4 25.7 13.6 0.90 No¹

1-Metylnaphthalene/

IA1PAH 9.99 9.81 8.87 0.94¹ 0.30 No¹

1-Metylnaphthalene/

IA2PAH 9.99 9.94 9.70 0.24 0.30 Yes

2-Metylnaphthalene/

IA1PAH 10.0 9.57 8.53 1.04¹ 0.30 No¹

2-Metylnaphthalene/

IA2PAH 10.0 9.66 9.60 0.06 0.30 Yes

Naphthalene/IA1PAH 110 109.7 99.2 10.5¹ 3.30 No¹

Naphthalene/IA2PAH 110 109.9 107.7 2.1 3.30 Yes

Phenanthrene/IA1PAH 20.0 16.9 15.6 1.39¹ 0.75 No¹

Phenanthrene/IA2PAH 20.0 19.5 16.4 3.12¹ 0.75 No¹

Pyrene/IA1PAH 20.0 16.2 15.1 1.09¹ 0.75 No¹

Pyrene/IA2PAH 20.0 17.7 15.5 2.29¹ 0.75 No¹

1) The difference is within the analytical error

Conclusion: Almost all criteria for stability were fulfilled when the analytical error was

considered with exception for fluorene in the sample IA2PAH. For this the results of participant indicate stability. Thus, the samples could be considered stable.

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APPENDIX 5 (1/1)

: Feedback from the proficiency test

FEEDBACK FROM THE PARTICIPANTS

Participant Comments to the results Action / Proftest SYKE 6 After the delivery of the preliminary result report the

participant informed that they had reported results for sample IA2PAH erroneously. The corrected results were two times higher than the reported results.

The reported results were partly outliers in the statistical handling. The calculated value was used as the assigned value, thus the erroneously reported results did not affect to the performance evaluation of the participants. If the result had been reported correctly, the result would have been satisfactory, with exceptions of unsatisfactory performance for

acenaphthene, anthracene, fluorene, and naphthalene. The participant can recalculate the z scores according to the Guide for participants [5].

FEEDBACK TO THE PARTICIPANTS Participant Comments

6 The participant did not report the expanded measurement uncertainties for measurands. Participant reported that the samples are analyzed with an accredited method. For the accredited methods the measurement uncertainties should be reported.

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APPENDIX 6 (1/1)

: Evaluation of the assigned values and their uncertainties

Measurand Sample Unit Assigned value Upt Upt, % Evaluation method of assigned value upt/spt

1-Methylnaphthalene IA1PAH ng/sample 9.99 0.46 4.6 Calculated value 0.23

IA2PAH ng/sample 9.99 0.46 4.6 Calculated value 0.23

2-Methylnaphthalene IA1PAH ng/sample 10.0 0.5 4.8 Calculated value 0.24

Acenaphthene IA1PAH ng/sample 110 7 6.1 Calculated value 0.31

IA2PAH ng/sample 110 7 6.1 Calculated value 0.31

Acenaphthylene IA1PAH ng/sample 210 13 6.3 Calculated value 0.32

Anthracene IA1PAH ng/sample 20.0 1.0 4.9 Calculated value 0.20

Fluoranthene IA1PAH ng/sample 30.0 1.6 5.4 Calculated value 0.18

Fluorene IA1PAH ng/sample 30.0 1.6 5.3 Calculated value 0.27

Naphthalene IA1PAH ng/sample 110 7 6.1 Calculated value 0.31

Phenanthrene IA1PAH ng/sample 20.0 1.0 4.9 Calculated value 0.20

Pyrene IA1PAH ng/sample 20.0 1.0 4.9 Calculated value 0.20

Upt = Expanded uncertainty of the assigned value

Criterion for reliability of the assigned value upt/spt < 0.3, where spt= the standard deviation for proficiency assessment upt= the standard uncertainty of the assigned value

If upt/spt < 0.3, the assigned value is reliable and the z scores are qualified [3].

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APPENDIX 7 (1/1)

: Terms in the results tables

Results of each participant

Measurand The tested parameter

Sample The code of the sample

z score Calculated as follows:

z = (xi - xpt)/spt, where

xi = the result of the individual participant

xpt = the assigned value

spt = the standard deviation for proficiency assessment Assigned value The value attributed to a particular property of a proficiency test item 2 × spt % The standard deviation for proficiency assessment (spt) at the 95 %

confidence level

Participant’s result The result reported by the participant (the mean value of the replicates)

Md Median

s Standard deviation

s % Standard deviation, %

nstat Number of results in statistical processing Summary on the z scores

S – satisfactory ( -2  z  2)

Q – questionable ( 2< z < 3), positive error, the result deviates more than 2 × spt from the assigned value q – questionable ( -3 < z < -2), negative error, the result deviates more than 2 × spt from the assigned value U – unsatisfactory (z ≥ 3), positive error, the result deviates more than 3 × spt from the assigned value u – unsatisfactory (z ≤ -3), negative error, the result deviates more than 3 × spt from the assigned value Robust analysis

The items of data are sorted into increasing order, x1, x2, xi,…,xp. Initial values for x^* and s^* are calculated as:

x^* = median of xi (i = 1, 2, ....,p)

s^* = 1.483 × median of ׀xi – x^*׀ (i = 1, 2, ....,p) The mean x^*and s^* are updated as follows:

Calculate φ = 1.5 × s^*. A new value is then calculated for each result xi (i = 1, 2 …p):

{ x^* - φ, if xi < x^* - φ xi*

= { x^* + φ, if xi > x^* + φ, { xi otherwise The new values of x^*and s^*are calculated from:

The robust estimates x^* and s^* can be derived by an iterative calculation, i.e. by updating the values of x^* and s^* several times, until the process convergences [2].

p x x^* ⁼



_i^*/



⁻ ⁻

= ^ ^

 1.134 (x x )²/(p 1)

s _i

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APPENDIX 8 (1/3)

: Results of each participant

Participant 1

Measurand Unit Sample z score Assigned value 2×spt % Participant's result Md Mean s s % nstat

1-Methylnaphthalene ng/sample IA1PAH 1.45 9.99 20 11.44 10.00 10.22 1.13 11.0 3

ng/sample IA2PAH 3.44 9.99 20 13.43 10.73 9.75 4.25 43.6 3

2-Methylnaphthalene ng/sample IA1PAH 1.85 10.0 20 11.9 10.8 10.6 1.3 12.6 3

ng/sample IA2PAH 2.83 10.0 20 12.8 10.6 9.5 3.9 41.3 3

Acenaphthene ng/sample IA1PAH 1.42 110 20 126 103 105 16 15.4 5

ng/sample IA2PAH 1.05 110 20 122 92 92 21 22.9 6

Acenaphthylene ng/sample IA1PAH -0.45 210 20 201 201 194 16 8.5 5

ng/sample IA2PAH -0.39 210 20 202 188 174 34 19.4 6

Anthracene ng/sample IA1PAH -1.24 20.0 25 16.9 16.9 18.6 4.0 21.7 5

ng/sample IA2PAH -0.06 20.0 25 19.9 17.8 16.6 3.4 20.7 6

Fluoranthene ng/sample IA1PAH -1.98 30.0 30 21.1 27.0 26.2 4.1 15.6 5

ng/sample IA2PAH -2.09 30.0 30 20.6 22.8 22.3 5.3 23.6 6

Fluorene ng/sample IA1PAH 0.16 30.0 20 30.5 29.0 28.8 4.4 15.2 5

ng/sample IA2PAH -0.23 30.0 20 29.3 26.5 25.3 4.4 17.4 6

Naphthalene ng/sample IA1PAH 2.67 110 20 139 118 114 24 21.3 6

ng/sample IA2PAH 6.06 110 20 177 107 113 38 33.8 6

Phenanthrene ng/sample IA1PAH 0.28 20.0 25 20.7 20.7 19.5 2.7 13.9 5

ng/sample IA2PAH 0.70 20.0 25 21.8 18.0 16.9 3.9 22.9 6

Pyrene ng/sample IA1PAH -2.40 20.0 25 14.0 18.0 17.6 3.1 17.6 5

ng/sample IA2PAH -1.92 20.0 25 15.2 17.0 16.2 2.9 17.7 5

Participant 2

Measurand Unit Sample z score Assigned value 2×spt % Participant's result Md Mean s s % nstat

Acenaphthene ng/sample IA1PAH -2.00 110 20 88 103 105 16 15.4 5

ng/sample IA2PAH -2.27 110 20 85 92 92 21 22.9 6

Acenaphthylene ng/sample IA1PAH -1.24 210 20 184 201 194 16 8.5 5

ng/sample IA2PAH -1.48 210 20 179 188 174 34 19.4 6

Anthracene ng/sample IA1PAH -1.60 20.0 25 16.0 16.9 18.6 4.0 21.7 5

ng/sample IA2PAH -0.80 20.0 25 18.0 17.8 16.6 3.4 20.7 6

Fluoranthene ng/sample IA1PAH -0.67 30.0 30 27.0 27.0 26.2 4.1 15.6 5

ng/sample IA2PAH -1.11 30.0 30 25.0 22.8 22.3 5.3 23.6 6

Fluorene ng/sample IA1PAH -1.67 30.0 20 25.0 29.0 28.8 4.4 15.2 5

ng/sample IA2PAH -1.67 30.0 20 25.0 26.5 25.3 4.4 17.4 6

Naphthalene ng/sample IA1PAH -0.09 110 20 109 118 114 24 21.3 6

ng/sample IA2PAH -0.36 110 20 106 107 113 38 33.8 6

Phenanthrene ng/sample IA1PAH -0.80 20.0 25 18.0 20.7 19.5 2.7 13.9 5

ng/sample IA2PAH -1.20 20.0 25 17.0 18.0 16.9 3.9 22.9 6

Pyrene ng/sample IA1PAH -0.80 20.0 25 18.0 18.0 17.6 3.1 17.6 5

ng/sample IA2PAH -1.20 20.0 25 17.0 17.0 16.2 2.9 17.7 5

-3 0 3