Report No. 735 Waters Proficiency Testing Round 135 - …capeyork.myownserver.net/~ptaasnau/documents/735.pdf · A z-score close to zero indicates that the result agrees well with

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Report No. 735

Waters Proficiency Testing

Round 135

- Total Recoverable Oil and Grease -

November 2011

Acknowledgments

PTA wishes to gratefully acknowledge the technical assistance provided for this program by Dr M Buckley-Smith and Dr R Hutchinson, Global Proficiency Ltd, New Zealand. Also our thanks go to Global Proficiency Ltd (Hamilton, New Zealand) and Global Proficiency Pty Ltd (Melbourne, Australia) for the supply and distribution of samples.

© Copyright Proficiency Testing Australia, 2011

PO Box 7507 SILVERWATER NSW 2128, Australia

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CONTENTS

1. Foreword............................................................................................................................1

2. Program Features and Design...........................................................................................1

3. Statistical Format ...............................................................................................................2

4. PTA and Technical Advisors' Comments...........................................................................5

5. Outlier Results…………………………………………………………………………………..12

6. References. .....................................................................................................................12

APPENDIX A – Results and Data Analysis

Total Recoverable Oil and Grease Vial 1……………………………...….……………........... A1

Total Recoverable Oil and Grease Vial 2 ……………...……………………………………… A4

APPENDIX B – Sample Homogeneity

Homogeneity Testing…………………………………….…………………………………………B1 APPENDIX C – Documentation

Instructions to Participants …………………………………………………………………………C1

Method Codes………………………………………………………………………………….…….C3

Results Sheet……………………………………………………………….………………………..C4

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1. Foreword

This report summarises the results of a proficiency testing program on the determination of total recoverable oil and grease in waters. This is round 135 in a planned series of programs involving the analysis of chemical and physical parameters of waters. The exercise was conducted in September 2011 by Proficiency Testing Australia (PTA). The main aim of the program was to assess laboratories’ abilities to competently perform the prescribed analyses.

The Program Coordinator was Ms Y Christie and the Technical Advisors were Dr M Buckley-Smith and Dr R Hutchinson from Global Proficiency Ltd. This report was authorised by Ms F Ward, PTA Quality - Business Development Manager.

2. Program Features and Design 2.1 Each laboratory was randomly allocated a unique code number for the program to

ensure confidentiality of results. Reference to each laboratory in this report is by code number only. Please note that a number of laboratories reported more than one set of results and, therefore, their code numbers (with letter) could appear several times in the same data set.

2.2 Laboratories were provided with the "Instructions to Participants" and "Results Sheet"

(see Appendix C). Laboratories were requested to perform the tests according to their routine methods.

2.3 Participants were provided with two sealed glass vials (labelled PTA 1 and PTA 2)

containing solutions of total recoverable oil and grease. 2.4 A total of 58 laboratories received samples, comprising:

- 44 Australian participants; and

- 14 overseas participants, including:

- Indonesia (1), Malaysia (5), New Zealand (1), Papua New Guinea (3), Pakistan (1), Singapore (1), Thailand (2).

Of these 58 laboratories, 3 were unable to submit results by the due date. 2.5 Results (as reported by participants) with corresponding summary statistics (i.e.

number of results, median, normalised interquartile range, robust coefficient of variation, uncertainty of median, minimum, maximum and range) are presented in Appendix A (for each sample and for each of the analyses performed).

2.6 A robust statistical approach, using z-scores, was utilised to assess laboratories’

testing performance (see Section 3). Robust z-scores, z-score charts and youden diagrams relevant to each test are presented in Appendix A.

The document entitled Guide to Proficiency Testing Australia, 2011 (reference [1]) defines the statistical terms and details the statistical procedures referred to in this report.

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2.7 A tabulated listing of laboratories (by code number) identified as having outlier results can be found on page 12.

2.8 Prior to sample distribution, a number of randomly selected samples were analysed

for homogeneity. Based on the results of this testing (see Appendix B) it was considered that the samples utilised for this program were homogenous. As such, any results later identified as outliers could not be attributed to any notable sample variability.

3. Statistical Format

For each test, where appropriate, the following information is given:

- a table of results and calculated z-scores;

- a list of summary statistics;

- ordered z-score charts; and

- Youden diagrams.

3.1 Outlier Results and Z-scores In order to assess laboratories’ testing performance, a robust statistical approach,

using z-scores, was utilised. Z-scores give a measure of how far a result is from the consensus value (i.e. the median), and gives a "score" to each result relative to the other results in the group.

A z-score close to zero indicates that the result agrees well with those from other

laboratories. Whereas, a z-score with an absolute value greater than or equal to 3.0 is considered to be an outlier and is marked by the symbol “§”.

Those results reported as “less than values” and marked with a “‡” are outlier results as they lie more than 3 normalised IQRs below the median.

Each determination was examined for outliers with all methods pooled. The table on page 12 summarises the outlier results detected.

3.2 Results Tables and Summary Statistics Each of these tables contains the results returned by each laboratory, including the

code number for the method used, and the robust z-score calculated for each result. Results have been entered exactly as reported by participants. That is, laboratories

which did not report results to the precision (i.e. number of significant figures) requested on the Results Sheet have not been rounded to the requested precision before being included in the statistical analysis.

A list of summary statistics appears at the bottom of each of the tables of results and consists of:

- the number of results for that test/sample (No. of Results);

- the median of these results, i.e. the middle value (Median);

- the normalised interquartile range of the results (Normalised IQR);

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- the robust coefficient of variation, expressed as a percentage (Robust CV) - i.e. 100 x Normalised IQR / Median;

- the uncertainty of the median;

- the minimum and maximum laboratory results; and

- the range (Maximum - Minimum).

The median is a measure of the centre of the data. The normalised IQR is a measure of the spread of the results. It is calculated by multiplying the interquartile range (IQR) by 0.7413, a factor which converts the IQR to an estimate of the standard deviation. The IQR is the difference between the upper and lower quartiles (i.e. the values above and below which a quarter of the results lie, respectively).

Please see reference [1] for further details on these robust summary statistics.

3.3 Ordered Z-Score Charts On these charts each laboratory's robust z-score is shown, in order of magnitude, and

is marked with its code number. From these charts, each laboratory can readily compare its performance relative to the other laboratories.

These charts contain solid lines at +3 and -3, so that outliers are clearly identifiable as

those laboratories whose "bar" extends beyond these "cut-off" lines. The y-axis of these charts has been limited, so very large z-scores appear to extend beyond the chart boundary.

3.4 Youden Diagrams

Youden two-sample diagrams are presented to highlight laboratory systematic differences. They are based on a plot of each laboratory's pair of results (i.e. sample two versus sample one) and represented by a black spot.

These diagrams also feature an approximate 95% confidence ellipse for the bivariate analysis of the results, and dashed lines which mark the median value for each of the samples.

All points which lie outside the ellipse are labelled with the laboratory's code number. Note however that these points may not correspond with those identified as outliers. This is because the outlier criteria (|z| ≥ 3.0) has a confidence level of approximately 99%, whereas the ellipse is an approximate 95% confidence region.

The points outside the ellipse on the Youden diagram will most probably be those with z-scores greater than 2 or less than -2. Laboratories which are outside the ellipse but have not been identified as outliers (i.e. have 2.0 < |z| < 3.0) are encouraged to review their results.

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As a guide to the interpretation of these diagrams:

(i) laboratories with significant systematic error components (i.e. between-

laboratory variation) will usually have results outside the ellipse in either the upper right hand quadrant (as formed by the median lines) or the lower left hand quadrant (i.e. unusually high or low results for both samples); and

(ii) laboratories with significant random error components (i.e. within-laboratory

variation) will have returned results that are substantially more variable than other participants, and these results will usually lie outside the ellipse in either the upper left or lower right hand quadrants (i.e. an unusually high result for one sample and low for the other).

Further details of the construction and interpretation of these diagrams is given in reference [1]. Please also refer to this document for a glossary of terms.

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4. PTA and Technical Advisors’ Comments 4.1 Overall analysis (all methods) Consensus values (median) derived from participant’s results are used in this program. These values are not metrologically traceable to an external reference. Sample preparation was undertaken according to Global Proficiency Ltd’s Standard Operating Procedures to ensure samples were fit-for-purpose, homogeneous and stable. Sample PTA 1 was prepared from high purity paraffinic mineral oil that had very low viscosity in distilled water, and PTA 2 was prepared from a mixture of sunflower oil, stearic acid and anhydrous milk fat (AMF) in distilled water. Samples were packaged in Teflon capped glass vials as a concentrate (~30 mL) quantity equivalent to 1 litre of wastewater. The doping levels for PTA 1 and PTA 2 are outlined in Table TA-1 below. Global Proficiency Ltd carried out 100% QC weight checks on all samples to ensure that variability on doping levels for all samples were less than 2.0%. Homogeneity and stability testing was also conducted (see Appendix B). Table TA-1. Manufacture concentrations and results for Total Recoverable Oil and Grease

Analyte Sample No. Dope Concentration (mg/L) ±*

Overall Median (mg/L)

PTA 1 47.12 ± 0.68 (1.45%) 40.75 Total Recoverable Oil and Grease PTA 2 58.84 ± 0.77 (1.31%) 52.70

*99% confidence interval (3 standard deviations) in mg/L and 3RSD. The Total Recoverable Oil and Grease testing was successfully carried out. When viewing the dataset as a whole, satisfactory results (|z-score| < 2) ranged between 26.7 – 54.8 mg/L for PTA 1 and 39.1 – 66.3 mg/L for PTA 2. Both of these ranges comfortably encompassed the doping concentration for each sample, although as expected there was a low bias as many laboratories under-recovered the oil and grease in each sample. This was most evident for sample PTA 2 which included stearic acid, and was more difficult to extract. Out of 53 participants, four questionable results (2.0<|z-score|<3.0) were obtained from the overall dataset for PTA 1 and two were obtained for PTA 2 (laboratories 138, 144, 145, 185, 227 and 402). Six overall dataset outlier results (|z-scores| ≥ 3.0) were obtained for PTA 1 and seven results for PTA 2, requiring follow-up action on behalf of laboratories 112, 195, 231, 274, 319, 402, 469, 509 and 539. In addition, laboratories 141, 144, 145, 185, 227, 400 and 499 may need to conduct an in-house investigation into their precision, as their standard deviation of repeatability was more than twice that of the average participant in this round. There was no obvious trend amongst these laboratories to say they struggled with a particular type of sample. The Total Recoverable Oil and Grease dataset formed a normal distribution for PTA 1 (the mineral oil sample), however there was a significant number of laboratories using APHA 5520B Liquid-liquid partition gravimetric method who recovered less than half of the oil and grease (vegetable/stearic/AMF) present in PTA 2 sample (Figures TA-1 and 2). Interestingly, there was a slightly high bias for laboratories using the infra-red method to test the mineral oil sample, with laboratories recovering oil and grease concentrations higher than the doping level in PTA 1 (47.12 mg/L) using this method (see section 4.2.3). This problem may be related to the mineral oil composition and difficulty of analysing an unknown sample. A single laboratory reported a less than result (“<”), where laboratory 138 was unable to recover the oil and grease in Sample PTA 1 and reported <0.1 mg/L. This result was marked

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with a “‡” and therefore an outlier, as the result was more than 3 normalised IQRs below the median.

Total Recoverable Oil and Grease - Result (mg/L) PT A 1

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100 110 120

Results (mg/L)

Fre

quen

cy

US EPA 1664A (Hexane, Grav)

Other

None given

Modified APHA 5520B (Liquid-Liquid)

Horiba Solvent Extraction

ASTM D 7066-04 (Infra Red)

APHA 5520G (Solid Phase)

APHA 5520D (Soxhlet)

APHA 5520C (Infra Red)

APHA 5520B (Liquid-Liquid)

Figure TA-1. Spread of results for Total Recoverable Oil and Grease proficiency testing of sample PTA 1, with a median of 40.75 mg/L.

Total Recoverable Oil and Grease - Result (mg/L) PT A 2

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100 110 120

Results (mg/L)

Fre

quen

cy


Other

None given




APHA 5520G (Solid Phase)




Figure TA-2. Spread of results for Total Recoverable Oil and Grease proficiency testing of sample PTA 2, with a median of 52.70 mg/L. The measurement uncertainty (MU) stated by participants can be seen in Figures TA-3 and 4, broken down by the methods used and giving an indication of the expected MU for these samples based on the reproducibility standard deviation (2SDR).

0 10 20 30 40 50 60 70 80 90 100 110 120

0 10 20 30 40 50 60 70 80 90 100 110 120

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Out of 53 participants, 24 (46%) submitted MU information. Many of the stated MU values did not accurately reflect the difference between the median and the participant’s result for each proficiency sample. The majority (71% and 74%) of participants stated that their MU was less than ±MU ≤ 6 mg/L for PTA 1 and ±MU ≤ 8 mg/L for PTA 2 respectively, however over 58% of these PTA 1 results and 39% of PTA 2 results varied from the median by greater than their stated MU.

Total Recoverable Oil and Grease - ±MU PTA 1

0

1

2

3

4

5

6

7

8

9

10

0 2 4 6 8 10 12 14 16 18 20 22 24

Measurement Uncertainty (mg/L)

Fre

quen

cy


Other

None given







Figure TA-3. MU stated by participants for Total Recoverable Oil and Grease testing of sample PTA 1.

Total Recoverable Oil and Grease - ±MU PTA 2

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12 14 16 18 20 22 24


Fre

quen

cy


Other

None given








2SDR

0 2 4 6 8 10 12 14 16 18 20 22 24


0 2 4 6 8 10 12 14 16 18 20 22 24

2SDR

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Laboratories 112, 131, 133, 141, 145, 185, 195, 219, 227, 319, 343, 345, 389, 400, 499, 509 and 539 may need to re-examine their MU calculations, as one or more of their results were further from the median than their stated MU. To keep it in perspective, confidence in the medians were 40.75 ± 1.21 mg/L for PTA 1, and 52.70 ± 1.19 mg/L for PTA 2. Interestingly, when the submitted MU were plotted by the means of calculation, the repeatability MU (MU r) were not all grouped at the low end of the MU scale with respect to the Reproducibility MU (MU R) values. The relatively even spread of MU values submitted can be seen in Figures TA-5 and 6 for PTA 1 and 2 respectively.

Total Recoverable Oil and Grease - R vs r. PTA 1

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10 11 12


Fre

quen

cy

±MU r.

±MU R


Total Recoverable Oil and Grease - R vs r. PTA 2

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8 9 10 11 12


Fre

quen

cy

±MU r.

±MU R

0 1 2 3 4 5 6 7 8 9 10 11 12

0 1 2 3 4 5 6 7 8 9 10 11 12

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Figure TA-6. MU stated by participants for Total Recoverable Oil and Grease testing of sample PTA 2. Using the t-value (outliers removed, 95% confidence interval) results indicated the estimate of reproducibility (~2SDR) for Total Recoverable Oil and Grease testing of PTA 1 was 40.75 ± 14.577 mg/L (35.77%) and PTA 2 was 52.70 ± 11.896 mg/L (22.57%). 4.2 Methods for determining Total Recoverable Oil and Grease 4.2.1 Partition Gravimetric Method (codes 1 and 2) Table TA-2. Partition Method results for Total Recoverable Oil and Grease

Round Sample No. Median (mg/L) Robust CV (%) No. of Participants

PTA 1 40.15 10.6 31 This round PTA 2 53.00 14.7 29

PTA Vial 1 22.00 25.15 36 Report no. 678 PTA Vial 2 30.2 12.8 36

PTA Vial 1 21.0 16.76 27 Report No. 606 PTA Vial 2 42.3 17.15 27

Using the t-value (outliers removed, 95% confidence interval) results submitted by laboratories using APHA 5520B Liquid-Liquid Partition-Gravimetric Method (nPTA 1,2=27,25) indicated a method reproducibility for PTA 1 of ± 11.547 mg/L (28.34%) and PTA 2 of ± 13.708 mg/L (26.01%) for Total Recoverable Oil and Grease testing. These are larger than the MU submitted by laboratories and in the published precision data from a single laboratory study using APHA 5520B which indicated the precision laboratories should be able to achieve was ± 17.4% (2RSD). APHA (2005) also indicated that precision for the Solid-Phase Partition-Gravimetric method (APHA 5520G) varied considerably with the matrix, and that precision could range between 6.4% - 61.6% (2RSD), so in light of this laboratories did very well with their reproducibility. The median recovery using the Partition-Gravimetric method was 85.2% for PTA 1 and 90.1% for PTA 2 when compared to the doping levels (Table TA-1). These recoveries were slightly lower than the APHA (2005) published value from a single laboratory study (93%) using APHA 5520B Liquid-liquid Partition-Gravimetric Method. APHA indicated that the Solid Phase Partition-Gravimetric method (APHA 5520G) was capable of recoveries between 87.1 – 92.5% which was closer to those seen in this current study, particularly with the inclusion of difficult to recover Stearic acid, in PTA 2.

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4.2.2 Hexane Extraction and Gravimetry Method (code 3) Table TA-3. Hexane Extractable Materials results for Total Recoverable Oil and Grease

Round Sample No. Median (mg/L) Robust CV (%) No. of Participants PTA 1 40.7 N/A 3 This round PTA 2 57.4 N/A 3

PTA Vial 1 N/A N/A 3 Report No. 678 PTA Vial 2 N/A N/A 3 PTA Vial 1 22.9 9.23 8 Report No. 606 PTA Vial 2 43.4 10.05 8

The low number of participants (3) using this method meant that statistical analysis could not be carried out, however, the median recovery for USEPA 1664A method was 40.7 mg/L (86.4%) for PTA 1 and 57.4 mg/L (97.6%) for PTA 2 based on the doping levels. 4.2.3 Infrared Method (codes 4, 5, 6, 7 and 8) Table TA-4. Hexane Extractable Materials results for Total Recoverable Oil and Grease

Round Sample No. Median (mg/L) Robust CV (%) No. of Participants PTA 1 58.5 N/A 5 This round PTA 2 56.1 N/A 5

A low number of participants (5) used this method, therefore statistical analysis was not able to be carried out, however the median recovery for infrared method was 58.5 mg/L (124.2%) for the mineral oil sample PTA 1, where infrared method tended to have a high bias well above the doping level; and 56.1 mg/L (95.3% recovery) for PTA 2 which contained sunflower oil, stearic acid and anhydrous milk fat. APHA 5520C indicated recoveries of 99% were achievable for fuel oils with precision of ±20% (2RSD). 4.2.4 Soxhlet Extraction Method (code 9) Table TA-5. Soxhlet Extraction Method results for Total Recoverable Oil and Grease

Round Sample No. Median (mg/L) Robust CV (%) No. of Participants

PTA 1 40.2 N/A 6 This round PTA 2 51.3 N/A 6

PTA Vial 1 17.60 33.7 7 Report No. 678 PTA Vial 2 24.90 11.6 7 PTA Vial 1 23.0 13.24 12 Report No. 606 PTA Vial 2 41.6 19.78 12

A low number of participants (6) used this method, therefore statistical analysis was not able to be carried out. Using the t-value (outliers removed, 95% confidence interval), results submitted by laboratories using APHA 5520D Soxhlet Extraction Method (nPTA 1,2=6,6) indicated a method reproducibility for PTA 1 of ± 17.924 mg/L (43.99%) and PTA 2 of ± 12.972 mg/L (24.61%) for Total Recoverable Oil and Grease testing. These precision results are considerably higher than those published in APHA (2005) for this method, which indicated 3.72% (2RSD) was achievable. The median recovery using this method was 40.2 mg/L (85.2%) for PTA 1 and 51.3 mg/L (87.2%) for PTA 2 based on the doping levels. These recovery percentages are a little lower

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than those published in APHA 5520D for Soxhlet Extraction of Total Recoverable Oil and Grease (98.7%). 4.2.5 Modified Method (code 10) One participant used this method code to identify the use of a modified version of APHA 5520B, the Liquid-liquid partition gravimetric method; therefore statistical analysis was not able to be carried out.

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5. Outlier Results

Laboratories reporting outlier results are listed in the following table:

Total Recoverable Oil and Grease Lab Code

PTA 1 PTA 2

112 § §

138 ‡

195 §

231 § §

274 §

319 § §

402 §

469 § §

509 §

539 §

1 A “§” indicates the occurrence of a z-score outlier result (i.e. those results for which

|z-score|≥3.0). 2 Laboratories returning results as “less than values” and where these results would lie more

than three normalised IQRs below the median have been marked with a “‡”, as these results are outliers.

6. References

[1] Guide to Proficiency Testing Australia, 2011 (This document can be found on the PTA website, www.pta.asn.au)

[2] APHA Standard Methods for Examination of Water and Wastewater, 2005, 21st Edition, APHA AWWA WEF.

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APPENDIX A

Results and Data Analysis

Total Recoverable Oil and Grease Vial 1……………...……………..…………………........... A1

Total Recoverable Oil and Grease Vial 2………..……...……………………………………… A4

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Total Recoverable Oil and Grease Results

Vial 1

A1

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Vial 1

Lab Code

Result (mg/L)

±MU

repeatabilityMU

reproducabilityRobust

z-score2Method

Code4

112 18.8 ± 3.3 # -3.13 § 11

115 38.7 # # -0.29 1

116 42.0 ± # 0.1 0.18 1

129 46.0 ± # 9.2 0.75 1

131 46.2 ± 5 # 0.78 9

133 42.7 ± 2.1 # 0.28 1

138 <0.1 # # NA ‡ 1

141 46.2 ± 3.69 # 0.78 9

144 38 # # -0.39 1

145 56.3 ± 5.3 # 2.21 5

157 40.8 ± 3.7 # 0.01 1

185 55.4 ± 6.4 # 2.09 10-1

195 36.5 ± 1 # -0.61 1

203 33.8 # # -0.99 1

219 47.2 ± 2.95 # 0.92 11

226 45.7 # # 0.70 11

227 58.5 ± 3.4 # 2.53 5

231 18.7 ± # 0.5 -3.14 § #

239 27.8 ± # 1 -1.84 3

251 29.3 # # -1.63 9

253 36.0 ± 5.0 # -0.68 1

258 40.7 ± # 6.8109 -0.01 1

263 32.5 # # -1.17 1

274 44.1 ± # 1.2 0.48 1

297 46.0 ± 8.9 # 0.75 1

301 40.7 ± 5.1 # -0.01 3

1

2

3

4

Total Recoverable Oil and Grease

Where reported, results are shown with their corresponding measurement uncertainty (MU).

"§"s denote outliers (i.e. those results for which |z-score | ≥ 3.0). Robust z-scores are calculated as: z = (A - median) ÷ normalised IQR, where A is the participant laboratory's result. Please note that z-scores are unable to be calculated for < or > results.


Please refer to Appendix C (page C3) for method code descriptions.

Results by Laboratory Code

A2

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Vial 1

Lab Code

Result (mg/L)

±MU

repeatabilityMU


z-score2Method

Code4

315 40.8 # # 0.01 2

316 46.3 ± # 4.5 0.79 1

319 19.4 ± 4.66 # -3.04 § 1

334 45.6 # # 0.69 11

338 41.2 ± 4 # 0.06 #

343 45.8 ± 4.6 # 0.72 1

345 38.5 ± 1.5 # -0.32 4

356 38.3 # # -0.35 9

389 39.5 ± 2.0 # -0.18 1

400 44.1 ± 8.8 # 0.48 1

402 20.8 # # -2.84 1

419 37.8 ± 6.6 # -0.42 1

421 40.5 ± 8.1 # -0.04 1

435 39.6 # # -0.16 1

441 41.5 # # 0.11 1

444 33.0 ± # 5.0 -1.10 9

459 31.8 ± # 2.9 -1.27 1

469 63.0 # # 3.17 § 5

488 42.1 # # 0.19 1

499 31.7 ± 0.219 # -1.29 1

509 63.0 ± 15.8 # 3.17 § #

517 38.7 # # -0.29 1

529 39.8 ± # 6.9 -0.14 1

536 28.7 # # -1.72 #

539 62.2 ± 6.8 # 3.05 § 4

540 46.6 ± # 7.6 0.83 3

549 42 ± # 8.7 0.18 9

53

40.75

7.02

1.21

17.2%

18.7

63.0

44.3

1

2

3

4

Total Recoverable Oil and Grease cont.


"§"s denote outliers (i.e. those results for which |z-score | ≥ 3.0). Robust z-scores are calculated as: z = (A - median) ÷ normalised IQR, where A is the participant laboratory's result. Please note that z-scores are unable to be calculated for < or > results.

Maximum:

Range:

Normalised IQR:

No of Results:


Minimum:



Median:

Uncertainty of the Median:

Robust CV:

A1

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Total Recoverable Oil and Grease - Vial 1 - Robust Z-Scores

Robust Z-Scores

Ordered R

obust Z-S

core Charts

A3

Total R

ecoverable Oil and G

rease - Vial 1

402

239

536

251 49

9

459 203 25

3 419

144

356

345

115

517

529

421

258

301

444

263 19

5

319

112

231

435

389

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

441

116

549

488

133

274

226

343

297

131

141

316

540

219

185 22

7 539

469

509

145

157

315

338 12

9

400

334

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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Total Recoverable Oil and Grease Results

Vial 2

A5

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Vial 2

Lab Code

Result (mg/L)

±±MU

repeatability±MU


z-score2Method

Code3

112 29.0 ± 3.3 # -3.49 § 11

115 47.2 # # -0.81 1

116 53.0 ± # 0.1 0.04 1

129 58.0 ± # 11.6 0.78 1

131 52.6 ± 5 # -0.01 9

133 55.9 ± 2.8 # 0.47 1

138 35.2 ± # 5.3 -2.58 1

141 44.8 ± 3.58 # -1.16 9

144 36 # # -2.46 1

145 51.3 ± 5.3 # -0.21 5

157 54.8 ± 5.0 # 0.31 1

185 52.8 ± 6.1 # 0.01 10-1

195 24.7 ± 1 # -4.13 § 1

219 48.8 ± 2.95 # -0.57 11

226 59.2 # # 0.96 11

227 53.5 ± 3.1 # 0.12 5

231 14.0 ± # 0.5 -5.71 § #

239 49.3 ± # 1 -0.50 3

251 42.9 # # -1.44 9

253 56.7 ± 9.0 # 0.59 1

258 54.4 ± # 6.8109 0.25 1

263 49.6 # # -0.46 1

274 23.4 ± # 0.1 -4.32 § 1

297 59.7 ± 11.5 # 1.03 1

301 57.4 ± 7.2 # 0.69 3

315 48.7 # # -0.59 2

1

2

3




"§"s denote outliers (i.e. those results for which |z-score | ≥ 3.0). Robust z-scores are calculated as: z = (A - median) ÷ normalised IQR, where A is the participant laboratory's result.


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Vial 2

Lab Code

Result (mg/L)

±±MU

repeatability±MU


z-score2Method

Code3

316 60.4 ± # 5.4 1.14 1

319 28.6 ± 6.86 # -3.55 § 1

334 55.7 # # 0.44 11

338 53.5 ± 5 # 0.12 #

343 58.0 ± 5.8 # 0.78 1

356 52.7 # # 0.00 9

389 45.1 ± 2.0 # -1.12 1

400 42.5 ± 8.5 # -1.50 1

402 23.2 # # -4.35 § 1

419 54.4 ± 9.8 # 0.25 1

421 49.1 ± 9.8 # -0.53 1

435 55.6 # # 0.43 1

441 54.4 # # 0.25 1

444 50.0 ± # 8.0 -0.40 9

459 49.9 ± # 3.0 -0.41 1

469 80.0 # # 4.02 § 5

488 51.7 # # -0.15 1

499 54.6 ± 0.242 # 0.28 1

509 47.9 ± 12.0 # -0.71 #

517 54.1 # # 0.21 1

529 58.4 ± # 10 0.84 1

536 46.1 # # -0.97 #

539 58.6 ± 6.4 # 0.87 4

540 60.3 ± # 9.8 1.12 3

549 56 ± # 11.6 0.49 9

51

52.70

6.78

1.19

12.9%

14.0

80.0

66.0

1

2

3


Total Recoverable Oil and Grease cont.


"§"s denote outliers (i.e. those results for which |z-score | ≥ 3.0). Robust z-scores are calculated as: z = (A - median) ÷ normalised IQR, where A is the participant laboratory's result.

Maximum:

Range:

Normalised IQR:

No of Results:

Median:

Uncertainty of the Median:

Robust CV:

Minimum:


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Total Recoverable Oil and Grease - Vial 2 - Robust Z-Scores

Robust Z-Scores

Ordered R

obust Z-S

core Charts

A6

Total R

ecoverable Oli and G

rease - Vial 2

195 31

9

112

138

144

400 38

9

536 509

315

219

421

239

263

145

488

131

141

251 11

5

274

402

231

444

459

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

227

338

517

258

419

441

435

334

549

253

301

129

343

529

539

297

540

316

469

226

356

185

116 13

3

499

157

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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Sample 1

Sam

ple

2

20 30 40 50 60

2040

6080

Total Recoverable Oil and Grease (mg/L)

509

539

469

274195

231

402

319

112

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APPENDIX B

Sample Homogeneity

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Homogeneity Testing Samples for this program were obtained from Global Proficiency Ltd, Hamilton, New Zealand. One hundred percent of samples underwent quality control weight checks to ensure a consistent mass of oil and grease was delivered to each vial. Sample PTA Vial 1 contained 47.12 mg ± 0.68 mg (3x Standard deviations = 99% CI) of mineral oil, and Sample PTA Vial 2 contained 58.84 mg ± 0.77 mg (99% CI) of the vegetable oil, stearic acid and anhydrous milk fat mixture. A random selection of 10 samples were chosen from Sample 1 and Sample 2. Seven of each sample were stored frozen, and 3 of each were subjected to 35ºC for 3 days for an accelerated ageing stability trial. On 15 August 2011, 7x homogeneity and 3x stability of each sample were sent to be analysed by Hill Laboratories for Oil and Grease. Hill Laboratories tested the samples by filtration through filter aid, Soxhlet extraction, and gravimetric determination of extracted Oil and Grease (APHA 5520 D 21st ed. 2005). All stability samples showed no significantly increased variability when compared to frozen homogeneity samples, and based on the assumption that the rate of ageing doubles with every 7ºC elevated temperature, these samples were assumed stable for >96 days (3days*2(35/7)) from the date of manufacture (10 August 2011). Table H-1. Extraction (Test) and Weight check (QC) of Oil and Grease Samples (mg/L)

Sample PTA 1 Sample PTA 2 Bottle # QC Test Bottle # QC Test Homog PTA 1 (a) 47.00 41.64 Homog PTA 1 (a) 58.80 55.44 PTA 1 (c) 47.10 40.66 PTA 1 (c) 58.70 54.18 PTA 1 (d) 46.40 34.25 PTA 1 (d) 59.00 55.44 PTA 1 (e) 47.20 42.00 PTA 1 (e) 58.80 56.28 PTA 1 (g) 47.20 39.65 PTA 1 (g) 59.00 57.75 PTA 1 (h) 46.80 36.86 PTA 1 (h) 59.60 56.91 PTA 1 (j) 46.80 43.26 PTA 1 (j) 58.60 49.77 Stability PTA 1*(b) 47.20 42.84 Stability PTA 1*(b) 58.90 50.82 After PTA 1*(f) 46.90 40.95 PTA 1*(f) 58.80 52.92 Incubat. PTA 1*(i) 46.80 35.45 PTA 1*(i) 58.40 50.19 RSD 0.54% 7.95% RSD 0.54% 5.37%

From statistical analyses based on the results of this testing and rigorous quality control, it was considered that all samples were sufficiently homogenous and stable, so that any results later identified as outliers should not be attributed to any notable sample variability.

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APPENDIX C

Documentation

Instructions to Participants………...……………………………………………………………… C1

Method Codes………..…………………………………………………………………….………. C3

Results Sheet………………………………………………………………………………………. C4

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PROFICIENCY TESTING AUSTRALIA

WATERS PROFICIENCY TESTING PROGRAM

CHEMICAL ANALYSIS ROUND 135 SEPTEMBER 2011

TOTAL RECOVERABLE OIL AND GREASE

INSTRUCTIONS TO PARTICIPANTS

***NOTE: Samples should be refrigerated upon receipt unti l ready to test***

Participants are requested to note the following before commencing the analysis of the samples. 1. Samples and Sample Preparation

i) Samples supplied by Global Proficiency Pty Ltd consist of two glass vials with

PTFE cap-liner, labelled PTA 1 and PTA 2. The vials contain Oil and Grease (in Water) in the range of 10-60 milligrams per litre (mg/L). These have been acid preserved, and should be refrigerated until ready to test.

ii) Record vial number. iii) Each vial is ready to test and is a concentrate equivalent to 1 Litre (1L) of

sample, the oil and grease have been weighed into the vial as such. Please regard the water volume as exactly 1000mL for any volume calculations, do not try to measure the volume of the water in the vial (20ml in 40 ml vial is n/a for calculations)

iv) To minimise the possibility of change in vial contents, do not open vial until

ready to begin analysis, and thoroughly rinse/extract the entire vial contents and any oil and grease clinging to lid or vial surfaces. Do not attempt to sub-sample.

Note: Please treat as an “unknown oil”.

Please note: where possible, proficiency testing sa mples must be treated as a routine laboratory sample.

2. Tests Requested For the sample prepared from the vial.

i) Total Recoverable Oil and Grease If unable to perform the above please note this on your Results Sheet.

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3. Safety i) Samples are for laboratory use only. ii) Participants should have sufficient experience and training to take the

necessary precautions when handling the vials, prepared samples, other chemicals required for the analysis, and materials for disposal.

iii) Use of safety glasses, gloves, and fume hoods, where appropriate during the

determinations, is recommended. 4. Reporting (a) For each vial only a single result on the Results Sheet, is requested.

(b) For statistical purposes report results to one decimal place, e.g. 10.1 mg/L.

*PTA recognises that this request may exceed the usual number of decimal places reported by laboratories.

(c) Report results in mg/L (i.e., the total mg extracted/sample treated as 1L for

reporting).

(d) In addition to reporting the results, record the method of analysis using the attached codes.

(e) Laboratories are also requested to calculate and report an estimate of

uncertainty measurement for each reported measurement result. All estimates of uncertainty of measurement must be given as a 95% confidence interval (coverage factor k ≈ 2) and reported in mg/L.

5. Testing should commence as soon as possible after receiving ampoules and

results reported NO LATER THAN 23 SEPTEMBER 2011 to:

Yvette Christie Proficiency Testing Australia PO Box 7507 SILVERWATER NSW 2128 AUSTRALIA Phone: +612 9736 8397 Fax: +612 9743 6664 Email: [email protected]

7. For this program your laboratory has been allocated the code number shown

on the attached Results Sheet. All reference to your laboratory in reports associated with the program will be through this code number, thus ensuring the confidentiality of your results.

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Method Codes to be used for the Results Sheet

ANALYSIS METHOD DESCRIPTION

METHOD REFERENCE CODE

APHA 5520B (Liquid-Liquid) 1 Partition-Gravimetric

APHA 5520G (Solid Phase) 2

Hexane Extraction & Gravimetry

US EPA 1664A 3

APHA 5520C 4

ASTM D 7066-04 5

ASTM D 3921-96 6

US EPA 413.2 7

Infrared

US EPA 418.1 8

Soxhlet Extraction APHA 5520D 9

Modified Method Please also specify original method

10


Other or In-house Please specify 11

Method Reference Key

(a) APHA “Standard Methods for the Examination of Water and Wastewater” 18th Edition (1992), 19th Edition (1995), 20th Edition (1998), 21st Edition (2005).

(b) ASTM American Society for Testing and Materials

(c) US EPA US Environmental Protection Agency

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PROFICIENCY TESTING AUSTRALIA

WATERS PROFICIENCY TESTING PROGRAM

CHEMICAL ANALYSIS ROUND 135

TOTAL RECOVERABLE OI L AND GREASE SEPTEMBER 2011

RESULTS SHEET

(mg/L) Laboratory Code

Vial PTA 1 Vial PTA 2 ANALYSIS

Result ±MU*

r ±MU* R Result

±MU*

r ±MU* R

METHODCODE


Please note: where possible, proficiency testing sa mples must be treated as a routine laboratory sample.

(a) For each prepared sample only a single result is requested. (b) Report results to one decimal place e.g. 10.1mg/L. PTA recognises that this request may exceed the usual number of decimal places

reported by laboratories. (c) Report results in milligrams per litre (mg/L) (d) MU* Laboratories Measurement Uncertainty (MU) if known for the result.

Please report ±MU in mg /L and enter in appropriate column depending on whether it was calculated using repeatability (r) or reproducibility (R) data, or please state other source.

___________________ ________________________________ DATE SIGNATURE

Return results NO LATER THAN 23 SEPTEMBER 2011 to: Yvette Christie Proficiency Testing Australia PO Box 7507 SILVERWATER NSW 2128 AUSTRALIA Phone: +612 9736 8397 Fax: +612 9743 6664 Email: [email protected]

W135 YC results sheet.doc

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- End of Report -

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Report No. 735 Waters Proficiency Testing Round 135 - …capeyork.myownserver.net/~ptaasnau/documents/735.pdf · A z-score close to zero indicates that the result agrees well with