Report No. 654 Waters Proficiency Testing Round 118...

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Report No. 654

Waters Proficiency Testing

Round 118

-Biochemical Oxygen Demand (BOD) Chemical Oxygen Demand (COD)

Total Organic Carbon (TOC)-

May 2010

Acknowledgments

PTA wishes to gratefully acknowledge the technical assistance provided for this program by Dr G K-C Low, Department of Environment, Climate Change and Water (NSW). Also our thanks go to Environmental Resource Associates (ERA) for the supply of samples and to AsureQuality Pty Limited (Melbourne) for distributing the samples.

© Copyright Proficiency Testing Australia, 2010

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 Adviser’s Comments ..........................................................................4

5. Outlier Results……………………………… ........................................................................6

6. Reference. .........................................................................................................................6

APPENDIX A – Results and Data Analysis

Biochemical Oxygen Demand (BOD)……………………….....................................................A1

Chemical Oxygen Demand (COD)………………………………………………………………...A5

Total Organic Carbon (TOC)..……………………………………………………………..………. A9

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 Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) in waters. This is round 118 in a planned series of programs involving the analysis of chemical and physical parameters of waters. The exercise was conducted in March 2010 by Proficiency Testing Australia (PTA). The main aim of the program was to assess laboratories’ abilities to competently perform the prescribed analyses. The Technical Adviser for this program was Dr G K-C Low from the Department of Environment, Climate Change and Water (NSW) and the Program Coordinator was Ms Y Christie.

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.

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

(see Appendix C). 2.3 Participants were provided with one sealed vial containing solutions of Biochemical

Oxygen Demand, Chemical Oxygen Demand, Total Organic Carbon. 2.4 A total of 64 laboratories received samples, comprising:

- 50 Australian participants; and

- 14 overseas participants, including:

- China (1), Indonesia (2), Japan (1), Malaysia (2), New Zealand (1), Singapore (4), Thailand (2) and Vietnam (1).

Of these 64 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, 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 and z-score charts relevant to each test are presented in Appendix A.

The document entitled Guide to Proficiency Testing Australia, 2008 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 extreme or outlier results can be found on page 6.

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 samples utilised for this program were homogenous. As such, any results later identified as extreme (on these samples) could not be attributed to any significant 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; and

- ordered z-score charts.

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 three is considered to be an outlier and is marked by the symbol “§”.

Each determination was examined for outliers with all methods pooled. The table on

page 6 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);

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

- the minimum and maximum laboratory results; and

- the range (Maximum - Minimum).

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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.

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4. PTA and Technical Adviser’s Comments 4.1 Robust CVs are comparable with those from previous programs:

Robust CV Comparison Table

Analyte Program Ampoule/Sample Median (mg/L)

Robust CV (%)

Biochemical Oxygen Demand (BOD)

This round Report No. 548 Report No. 427

1

A7002

N169 N170

68.40

118

91

200

19.7

13

14 14

Chemical Oxygen Demand (COD)

This round Report No. 548 PTAC No. 354

1

A7002

N143 N144

110.0

192

270 273

9.4

7.4

3 4

Total Organic Carbon (TOC)

This round Report No. 548 PTAC No. 354

1

A7002

N143 N144

43.85

77

107 107

5.2

4.3

3 4

With reference to Biochemical Oxygen Demand, Chemical Oxygen Demand and Total Organic Carbon tests, the robust CVs are greater for this round when comparing to the previous rounds. The larger CVs may be due to lower concentrations (medians) for Biochemical Oxygen Demand, Chemical Oxygen Demand and Total Organic Carbon in this sample. 4.2 Outliers are identified on page 6. Laboratories receiving an outlier should examine their procedures to determine, if possible, the reason(s) for error. 4.3 BOD Outliers

Participants’ investigations of outlier results from previous programs revealed errors due to: • Incorrect dilutions; • Failure to calibrate dissolved oxygen meters; • Transcription errors; • Contamination of dilution water; • Evaporation of water seals during incubation; • Seeding not used or seeds not properly activated when required; and • High dissolved oxygen in blank due to algae growth in plastic tubing.

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4.4 COD Outliers

Previous programs have revealed errors due to:

• Contamination of deionised water (organic material from deioniser resin column); • Transcription errors; • Calculation errors; and • Contamination from glassware not properly cleaned. COD is an empirical test and strict adherence to the method of analysis is required.

4.5 TOC Outliers

Previous programs have revealed errors due to:

• Calibration standards; • Incorrect dilutions; • Transcription errors; and • Instrument malfunctions.

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5. Outlier Results

Laboratories reporting outlier results are listed in the following table:

Analysis

Lab Code

Biochemical

Oxygen Demand

Chemical Oxygen Demand

Total Organic Carbon

628 §

676 §

683 §

689 §

690 §

765 § § §

784 §

789 §

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

for which |z-score|>3). 6. Reference

[1] Guide to Proficiency Testing Australia, 2008 (This document can be found on the PTA website, www.pta.asn.au)

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APPENDIX A

Results and Data Analysis

Biochemical Oxygen Demand (BOD)……………………………...………………………….......A1

Chemical Oxygen Demand (COD)………………………………………………………………...A5

Total Organic Carbon (TOC)……………………………………………………………………..... A9

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Biochemical Oxygen Demand (BOD) Results

Ampoule 1

A1

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Ampoule 1

Lab Code

Result ± MU1

(mg/L)

Robust

z-score2Method

Code3

605 69 ± 22 0.04 1

607 73.6 ± 4.3 0.39 1

611 75.0 ± 12 0.49 1

613 63.0 ± 13 -0.40 1

617 87 ± 1 1.38 2

623 52 ± 15 -1.22 3

625 64 ± 12.8 -0.33 #

627 76.7 ± 15.3 0.62 1

628 61.5 ± 8.7 -0.51 1

640 75.6 ± 18.5 0.53 1

644 60.3 ± 11.2 -0.60 1

649 82.0 ± 20.5 1.01 1

651 68.4 ± 11 0.00 1

654 67 ± 9.6 -0.10 1

658 77.2 ± 7.72 0.65 1

659 70 # 0.12 1

663 67.7 ± 17 -0.05 1

669 73 # 0.34 1

676 28 ± 2.8 -3.00 § 1

683 75 ± 20 0.49 #

688 70.0 ± 6.6 0.12 1

689 23 # -3.37 § 1

691 48 ± 5.8 -1.51 1

692 45 ± 7.46 -1.74 1

693 69 # 0.04 1

703 57.3 ± 11 -0.82 1

706 79.0 ± 10.9 0.79 1

708 70.0 ± 21.93 0.12 1

710 77.4 ± 10 0.67 1

713 56.6 ± 5.0 -0.88 3

1

2

3

4

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

"§"s denote outliers (i.e. those results for which |z-score | ≥ 3). Robust z-scores are calculated as: z = (A - median ) ÷ normalised IQR , where A is the participant laboratory's result.

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

"#" indicates that no response was provided.

Results by Laboratory Code


A2

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Ampoule 1

Lab Code

Result ± MU1

(mg/L)

Robust

z-score2Method

Code3

714 62.0 ± 24 -0.48 1

717 68.0 ± 10.2 -0.03 1

721 52 ± 6.5 -1.22 1

729 54.7 ± 9.8 -1.02 1

733 77.5 ± 12 0.68 1

735 34 # -2.55 1

740 71.2 ± 10 0.21 1

748 84 ± 8 1.16 1

752 67.0 ± 12 -0.10 1

756 76 ± 28.5 0.56 1

759 101 ± 16 2.42 1

762 77 ± 15 0.64 1

765 26 # -3.18 § 1

768 64 # -0.30 1

770 50 # -1.37 3

773 60 # -0.61 1

779 79 # 0.79 1

784 85 # 1.22 1

786 68.4 # 0.00 3

787 49.9 # -1.37 #

789 65.0 # -0.25 1

794 73.883 # 0.41 1

838 75.2 ± 17.7 0.50 1

841 72.5 # 0.30 3

1004 30.800 ± 1.600 -2.79 1

1017 39.1 ± 0.8 -2.17 1

56

68.40

13.47

19.7%

23.0

101.0

78.0

1

2

3

4


"§"s denote outliers (i.e. those results for which |z-score | ≥ 3). Robust z-scores are calculated as: z = (A - median ) ÷ normalised IQR , where A is the participant laboratory's result.




Biochemical Oxygen Demand (BOD) cont.

Maximum:

Range:

Normalised IQR:

No of Results:

Median:

Robust CV:

Minimum:

A1

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Biochemical Oxygen Demand (BOD) - Ampoule 1 - Robus t Z-Scores

Robust Z-Scores

Ordered R

obust Z-S

core Charts

A3

Biochem

ical Oxygen D

emand (B

OD

) - Am

poule 1

1004 73

5

1017 69

2

691

787

721

729

703

773

644

628

714

613

623

770 71

3

676

765

689

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

654

752

663

717

651

786

659

688

740

841

669

607

794

611

625

768

789

708

605

693

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

A2

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Biochemical Oxygen Demand (BOD) - Ampoule 1 - Robus t Z-ScoresO

rdered Robust Z

-Score C

harts

Biochem

ical Oxygen D

emand

(BO

D) - A

mpoule 1 cont.

A475

6

627

762

658

710

733 64

9

748

617

759

683

838

640 78

4

706

779

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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Chemical Oxygen Demand (COD) Results

Ampoule 1

A5

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Ampoule 1

Lab Code

Result ± MU1

(mg/L)

Robust

z-score2Method

Code3

605 117 ± 5 0.67 5

607 107 ± 6 -0.29 6

611 97.3 ± 12 -1.22 6

613 116 ± 18 0.58 5

617 109 ± 1 -0.10 6

623 101 ± 9 -0.87 6

625 80 ± 16 -2.89 #

627 82.2 ± 20.6 -2.68 6

628 148 ± 8.7 3.66 § 4

640 115 ± 18 0.48 6

642 117 ± 18.3 0.67 6

644 114 ± 9.8 0.39 4

649 102 # -0.77 6

654 120 ± 6.8 0.96 6

658 118 ± 6 0.77 6

663 118 ± 12 0.77 6

669 80 # -2.89 4

676 111 ± 1 0.10 6

683 77 ± 23 -3.18 § #

685 120 ± 5.8 0.96 6

688 108 ± 4.2 -0.19 6

691 83 ± 4.6 -2.60 6

692 126 # 1.54 6

693 111 # 0.10 4

703 97.1 ± 23 -1.24 4

706 88.8 ± 10.7 -2.04 6

708 111.0 ± 17.86 0.10 4

710 103 ± 10 -0.67 6

713 107.4 ± 6.0 -0.25 11

714 134 ± 50 2.31 #

1

2

3

4




"§"s denote outliers (i.e. those results for which |z-score | ≥ 3). Robust z-scores are calculated


as: z = (A - median ) ÷ normalised IQR , where A is the participant laboratory's result.


A6

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Ampoule 1

Lab Code

Result ± MU1

(mg/L)

Robust

z-score2Method

Code3

717 112 ± 11.8 0.19 5

721 114 ± 28.5 0.39 6

729 116 ± 12 0.58 4

733 124 ± 10 1.35 4

735 100 # -0.96 4

740 130 ± 15 1.93 6

745 113 ± 12.7 0.29 4

748 113 ± 6 0.29 6

752 106 ± 11 -0.39 4

756 90 ± 7.7 -1.93 6

765 60.8 # -4.74 § 4

768 107 # -0.29 5

770 104 # -0.58 5

773 123.8 # 1.33 4

779 107 # -0.29 6

784 107 ± 3.88 -0.29 5

786 123 # 1.25 11

787 104 # -0.58 #

789 108 # -0.19 6

794 106.820 # -0.31 5

838 123 ± 18 1.25 5

1004 125.356 ± 2.538 1.48 4

1017 110 ± 6 0.00 5

53

110.0

10.4

9.4%

60.8

148.0

87.2

1

2

3

4

Chemical Oxygen Demand (COD) cont.




Maximum:

Range:

Normalised IQR:

No of Results:

Median:

Robust CV:


Minimum:



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Chemical Oxygen Demand (COD) - Ampoule 1 - Robust Z -Scores

Robust Z-Scores

Ordered R

obust Z-S

core Charts

A7

Chem

ical Oxygen D

emand - A

mpoule 1

669

627

691 70

6

756 70

3 623

649

770

787

752

794

735

611 71

0

625

683

765-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

784

713

688

789

617

1017

708

717

748

644

721

640

607

768

779

745

676

693

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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Chemical Oxygen Demand - Ampoule 1 - Robust Z-Score sO

rdered Robust Z

-Score C

harts

Chem

ical Oxygen D

emand

(CO

D) - A

mpoule 1 cont.

A8

642

658

663

654

685 786

733

1004 74

0 714

628

613

729

605 69

2

838

773

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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Total Organic Carbon (TOC) Results

Ampoule 1

A9

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Ampoule 1

Lab Code

Result ± MU1

(mg/L)

Robust

z-score2Method

Code3

605 44.5 ± 5.3 0.29 12

611 44.6 ± 4.4 0.33 12

613 43.7 ± 7 -0.07 12

617 50.5 ± 0.1 2.92 14

625 42 ± 8.4 -0.81 #

627 42.7 ± 10.7 -0.50 12

642 42.8 ± 6.75 -0.46 14

649 45.0 ± 2.25 0.50 12

659 44 # 0.07 12

669 49.5 # 2.48 13

676 43 ± 3.3 -0.37 12

681 44.4 ± 3.1 0.24 12

690 8820 # 3850.03 § 12

706 45.9 ± 4.4 0.90 12

708 46.5 ± 4.99 1.16 12

713 45.9 ± 2.0 0.90 17

720 40.3 ± 3.0 -1.56 13

729 41.3 ± 3.3 -1.12 12

748 43.3 ± 2 -0.24 12

752 43.7 ± 4.8 -0.07 12

765 36.1 # -3.40 § 12

768 41.3 # -1.12 12

770 43 # -0.37 12

773 45.5 # 0.72 12

784 37.0 # -3.01 § 12

786 45.9 # 0.90 17

789 35.2 ± 1.8 -3.79 § 12

794 45.016 # 0.51 17

28

43.85

2.28

5.2%

35.2

8820

8784.8

1

2

3

4

Minimum:








Maximum:

Range:

Normalised IQR:

No of Results:

Median:

Robust CV:

A9

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Total Organic Carbon (TOC) - Ampoule 1 - Robust Z-S cores

A10

Total O

rganic Carbon (T

OC

) - A

mpoule 1

Ordered R

obust Z-S

core Charts

720 72

9

768 62

5 627

642

748

613

659

681

605

611

649

794 71

3

786

708

669 61

7

690

770

676 75

2

784

765

789

706

773

-5

-4

-3

-2

-1

0

1

2

3

4

5

lab code

z-sc

ore

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APPENDIX B

Sample Homogeneity

B1

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Homogeneity Testing Samples for this program were obtained from the Environmental Resource Associates (ERA). As such, all samples are subjected to rigorous stability and homogeneity testing. On the basis of this testing, the ampoules utilised for this program were considered to be homogeneous.

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APPENDIX C

Documentation

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

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

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

C1

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PROFICIENCY TESTING AUSTRALIA

WATERS PROFICIENCY TESTING PROGRAM

CHEMICAL ANALYSIS ROUND 118 March 2010 BIOCHEMICAL OXYGEN DEMAND (BOD)

CHEMICAL OXYGEN DEMAND (COD)

TOTAL ORGANIC CARBON (TOC)

INSTRUCTIONS TO PARTICIPANTS

Please note the following before commencing the analysis of the samples. 1. Samples i) One sealed vial supplied by Environmental Resource Associates (ERA). The

vial contains BOD, COD, TOC concentrates. ii) Aliquot from the ampoule will require 200-fold dilution in reagent grade water. Please note: where possible, proficiency testing s amples must be treated as a

routine laboratory sample. 2. Sample Preparation Caution: Analysis must begin immediately after ampoule is opened.

i) Adjust ampoule temperature to 20º C ii) Add approximately 100 - 200 millilitres (mL) deionized water to a one-litre

volumetric flask. iii) Shake the vial prior to opening.

iv) Using a volumetric pipette, volumetrically pipette 5.0 mL of the concentrate into

the 1000 mL volumetric flask.

v) Dilute the flask to the final volume with deionized water. vi) Cap the flask and mix contents well.

vii) Immediately analyse the diluted sample by your normal procedures. viii) Report your result as mg/L for the diluted sample.

3. Tests Requested

C2

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For the sample prepared from the ampoule.

i) Biochemical Oxygen Demand (BOD) ii) Chemical Oxygen Demand (COD) iii) Total Organic Carbon (TOC)

If unable to perform the above please note this on your Results Sheet. 4. Safety i) The sample is for laboratory use only. ii) Participants should have sufficient experience and training to take the

necessary precautions when handling the ampoule, 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. 5. Reporting (a) Report results using three significant figures. For non detection, report results

using < preceding the laboratory's reporting limit. (b) Report results in milligrams per litre (mg/L).

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

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

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

6. Testing should commence as soon as possible after receiving the ampoule and

results reported NO LATER THAN 19 MARCH 2010 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.

C3

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Method Codes to be used for the Results Sheet

ANALYSIS METHOD REFERENCE CODE SM 19, SM 20, SM 21, (5210B) 1

USEPA (0405.1) 2 Biochemical Oxygen Demand (BOD)

Other (please specify) 3

SM 19, SM 20, SM 21, (5220B) 4

SM 19, SM 20, SM 21 (5220C) 5

SM 19, SM 20, SM 21 (5220D) 6

USEPA (0410.1) 7

USEPA (0410.2) 8

USEPA (0410.3) 9

USEPA (0410.4) 10



SM 19, SM 20, SM 21 (5310B) 12

SM 19, SM 20, SM 21 (5310C) 13

SM 19, SM 20, SM 21 (5310D) 14

USEPA (0415.1) 15

USEPA (0415.2) 16



Method Reference Key

(a) SM 19, SM 20, SM 21 APHA “Standard Methods for the Examination

of Water and Wastewater” 19th Edition (1995), 20th Edition (1998), 21st Edition (2005)

(b) USEPA USEPA 600/4 – 79 - 020

C4

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PROFICIENCY TESTING AUSTRALIA

WATERS PROFICIENCY TESTING PROGRAM

CHEMICAL ANALYSIS ROUND 118

BIOCHEMICAL OXYGEN DEMAND (BOD) CHEMICAL OXYGEN DEMAND (COD) TOTAL ORGANIC CARBON (TO C) MARCH 2010

RESULTS SHEET

(mg/L)

Laboratory Code

ANALYSIS Result ±MU* METHOD CODE




Please note: where possible, proficiency tes ting samples must be treated as a routine laboratory sample.

(a) For each prepared sample (diluted from the ampoule) only a single result is requested.

(b) Report results using three significant figures. For compounds not found, report results using < preceeding the laboratory's reporting limit

(c) Report results in milligrams per litre (mg/L)

(d) MU* Laboratories Measurement Uncertainty (MU) if known for the result. Please report in mg /L

______________________ ________________________________ DATE SIGNATURE

Return results NO LATER THAN 19 MARCH 2010 to Yvette Christie Proficiency Testing Australia PO Box 7507 SILVERWATER NSW 2128 AUSTRALIA Phone: +612 9736 8397 Fax: +612 9743 6664 Email: [email protected]

INSTRUCT WATERS PROF TEST PROG 118

«Code»

D1

SD 9.17.01

- End of Report -

Report No. 654 Waters Proficiency Testing Round 118...

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