NISTIR 7880

NIST Micronutrients Measurement

Quality Assurance Program

Winter 2012 Comparability Studies

Results for Round Robin LXXI

Fat-Soluble Vitamins and Carotenoids in Human Serum

and Round Robin 36 Ascorbic Acid in Human Serum

David L. Duewer

Jeanice B. Thomas

http://dx.doi.org/10.6028/NIST.IR.7880

NISTIR 7880

NIST Micronutrients Measurement

Quality Assurance Program

Winter 2012 Comparability Studies

Results for Round Robin LXXI

Fat-Soluble Vitamins and Carotenoids in Human Serum

and Round Robin 36 Ascorbic Acid in Human Serum

David L. Duewer

Jeanice B. Thomas

Materials Measurement Laboratory

http://dx.doi.org/10.6028/NIST.IR.7880

December, 2012

U.S. Department of Commerce 

Rebecca Blank, Acting Secretary

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
ii

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Abstract 

The National Institute of Standards and Technology coordinates the Micronutrients Measurement 

Quality Assurance Program (MMQAP) for laboratories that measure fat- and water-soluble vitamins 

and carotenoids in human serum and plasma. This report describes the design of and results for the 

Winter 2012 MMQAP measurement comparability improvement studies: 1) Round Robin LXXI 

Fat-Soluble Vitamins and Carotenoids in Human Serum and 2) Round Robin 36 Total Ascorbic Acid 

in Human Serum. The materials for both studies were shipped to participants in mid-January 2012; 

participants were requested to provide their measurement results by April 16, 2012. 

Keywords 

Human Serum 

Retinol, α-Tocopherol, γ-Tocopherol, Total and Trans-β-Carotene 

Total Ascorbic Acid

 iii 
 iv 

Table of Contents 

Abstract...............................................................................................................................................iii 

Keywords............................................................................................................................................iii 

Table of Contents............................................................................................................................... iv 

Introduction......................................................................................................................................... 1 

Round Robin LXXI: Fat-Soluble Vitamins and Carotenoids in Human Serum......................... 1 

Round Robin 36: Vitamin C in Human Serum............................................................................... 2 

References............................................................................................................................................ 3 

Appendix A. Shipping Package Inserts for RR71........................................................................ A1 

Appendix B. Final Report for RR71 ..............................................................................................B1 

Appendix C. All-Lab Report for RR71..........................................................................................C1 

Appendix D. Representative Individualized Report for RR71................................................... D1 

Appendix E. Shipping Package Inserts for RR36.........................................................................E1 

Appendix F. Final Report for RR36............................................................................................... F1 

Appendix G. “All-Lab Report” for RR36 .................................................................................... G1 

Appendix H. Representative “Individualized Report” for RR36............................................... H1 
Introduction 

Beginning in 1988, the National Institute of Standards and Technology (NIST) has coordinated the 

Micronutrients Measurement Quality Assurance Program (MMQAP) for laboratories that measure 

fat- and water-soluble vitamins and carotenoids in human serum and plasma. The MMQAP 

provides participants with measurement comparability assessment through use of interlaboratory 

studies, Standard Reference Materials (SRMs) and control materials, and methods development and 

validation. Serum-based samples with assigned values for the target analytes (retinol, alphatocopherol, gamma/beta-tocopherol, trans- and total beta-carotene, and total ascorbic acid) and 

performance-evaluation standards are distributed by NIST to laboratories for analysis. 

Participants use the methodology of their choice to determine analyte content in the control and 

study materials. Participants provide their data to NIST, where it is compiled and evaluated for 

trueness relative to the NIST value, within-laboratory precision, and concordance within the 

participant community. NIST provides the participants with a technical summary report concerning 

their performance for each exercise and suggestions for methods development and refinement. 

Participants who have concerns regarding their laboratory’s performance are encouraged to consult 

with the MMQAP coordinators. 

All MMQAP interlaboratory studies consist of individual units of batch-prepared samples that are 

distributed to each participant. For historical reasons these studies are referred to as “Round 

Robins”. The MMQAP program and the nature of its studies are described elsewhere. [1,2] 

Round Robin LXXI: Fat-Soluble Vitamins and Carotenoids in Human Serum 

Participants in the MMQAP Fat-Soluble Vitamins and Carotenoids in Human Serum Round Robin 

LXXI comparability study (hereafter referred to as RR71) received five liquid-frozen human serum 

test samples for analysis. Unless multiple vials were previously requested, participants received one 

vial of each serum. These sera were shipped on dry ice to participants mid-January 2012. The 

communication materials included in the sample shipment are provided in Appendix A. 

Participants are requested to report values for all fat-soluble vitamin-related analytes that are of 

interest to their organizations. Not all participants report values for the target analytes, and many 

participants report values for non-target analytes. 

The final report delivered to every participant in RR71 consists of three documents: 

 A cover letter for the current study, a brief description of the other two documents, and a 

discussion of our analysis of the overall results that may be of broad interest. This cover 

letter is reproduced as Appendix B. 

 The “All-Lab Report” that lists all of the reported measurement results, a number of 

consensus statistics for analytes reported by more than one participant, and the mean median 

and pooled SD from any prior distributions of the serum. This report also provides a 

numerical “score card” for each participant’s measurement comparability for the more 

commonly reported analytes. This All-Lab Report is reproduced as Appendix C. 

 1 
 An “Individualized Report” that graphically analyzes each participant’s results for all 

analytes reported by at least five participants. This report also provides a graphical summary 

of their measurement comparability. The graphical tools used in the Individualized Report 

are described in detail elsewhere [3]. An example Individualized Report is reproduced as 

Appendix D. 

Round Robin 36: Vitamin C in Human Serum 

Participants in the MMQAP Vitamin C in Human Serum Round Robin 36 comparability study 

(hereafter referred to as RR36) received four frozen serum test samples, one frozen control serum, 

and a solid ascorbic acid control material for analysis. Unless multiple vials were previously 

requested, participants received one vial of each material. These sample materials were shipped on 

dry ice to participants mid-January 2012. The communication materials included in the sample 

shipment are provided in Appendix E. 

The test and control serum materials were prepared by adding equal volumes of 10 % 

metaphosphoric acid (MPA) to human serum that had been spiked with ascorbic acid. While these 

samples contain some dehydroascorbic acid, its content is variable. Therefore, the participants 

report only total ascorbic acid (TAA, ascorbic acid plus dehydroascorbic acid). Participants are also 

encouraged to prepare calibration solutions from the supplied solid control to enable calibrating their 

serum measurements to the same reference standard. 

The final report delivered to every participant in RR36 consists of three documents: 

 A cover letter for the current study, a brief description of the other two documents, and a 

discussion of our analysis of overall results that may be of broad interest. This cover letter is 

reproduced as Appendix F. 

 The “All-Lab Report” that summarizes all of the reported measurement results and provides 

several consensus statistics. This All-Lab Report is reproduced as Appendix G. 

 An “Individualized Report” that graphically analyzes each participant’s results for TAA, 

including a graphical summary of their measurement comparability. The graphical tools 

used in the Individualized Report are described in detail elsewhere [3]. An example 

Individualized Report is reproduced as Appendix H. 

 2 
 3 

References 

1 Duewer DL, Brown Thomas J, Kline MC, MacCrehan WA, Schaffer R, Sharpless KE, May WE, 

Crowell JA. NIST/NCI Micronutrients Measurement Quality Assurance Program: Measurement 

Repeatabilities and Reproducibilities for Fat-Soluble Vitamin-Related Compounds in Human 

Sera. Anal Chem 1997;69(7):1406-1413. 

2 Margolis SA, Duewer DL. Measurement Of Ascorbic Acid in Human Plasma and Serum: 

Stability, Intralaboratory Repeatability, and Interlaboratory Reproducibility. Clin Chem 

1996;42(8):1257-1262. 

3 Duewer DL, Kline MC, Sharpless KE, Brown Thomas J, Gary KT, Sowell AL. Micronutrients 

Measurement Quality Assurance Program: Helping Participants Use Interlaboratory Comparison 

Exercise Results to Improve Their Long-Term Measurement Performance. Anal Chem 

1999;71(9):1870-1878. 
Appendix A. Shipping Package Inserts for RR71 

The following three items were included in each package shipped to an RR71 participant: 

 Cover letter 

 Datasheet 

 Packing List and Shipment Receipt Confirmation Form 

The cover letter and datasheet were enclosed in a sealed waterproof bag along with the samples 

themselves. The packing list was placed at the top of the shipping box, between the cardboard 

covering and the foam insulation. 

A1
January 2, 2012 

Dear Colleague: 

UNITED STATES DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Gaithersburg, Maryland 20899-

Enclosed are samples for the first fat-soluble vitamins and carotenoids in serum study (Round Robin 

LXXI) for the 2012 NIST Micronutrients Measurement Quality Assurance Program. The set of samples 

(Sera 382- 386) consists of one vial each of five liquid-frozen serum samples for analysis along with a 

form for reporting your results. These samples should be stored in the dark at or below -20 °C upon 

receipt. When reporting your results, please submit one value for each analyte for a given serum sample. 

If a value obtained is below your limit of quantification, please indicate this result on the form by using 

NQ (Not Quantified). Results are due to NIST by Apri116, 2012. Results received more than two weeks 

after the due date may not be included in the summary report for this round robin study. The feedback 

report concerning the study will be distributed in May 2012. 

Samples should be allowed to stand at room temperature under subdued light until thawed. We 

recommend that sample mixing be facilitated with 3 to 5 min agitation in an ultrasonic bath or at least 15 

min at room temperature with intermittent swirling. (CAUTION: Vigorous shaking will cause foaming 

and possibly interfere with accurate measurement. The rubber stopper contains phthalate esters that may 

leach into the sample upon intermittent con.tact of the liquid sample with the stopper. These esters absorb 

strongly in the UV region and elute near retinol in most LC systems creating analytical problems.) 

Water should not be added to the liquid-frozen samples. 

For consistency, we request that laboratories use the following absorptivities ( dL/g • em): retinol, 1843 at 

325 nm (ethanol); retinyl palmitate, 975 at 325 nm (ethanol); a -tocopherol, 75.8 at 292 nm (ethanol); ytocopherol, 91.4 at 298 nm (ethanol); a-carotene, 2800 at 444 nm (hexane); 13-carotene, 2560 at 450 nm 

(ethanol), 2592 at 452 nm (hexane); and lycopene, 3450 at 472 nm (hexane). 

Please report your results for Round Robin LXXI by e-mail to david.duewer@nist.gov or fax to 301-977-

0685. If you have questions or comments regarding this study, please call me at (301) 975-3120 or e-mail 

me atjbthomas@nist. 

NISI 

A2
Participant #: ________ Date: _____________

Analyte 382 383 384 385 386 Units*

total retinol 

trans-retinol

retinyl palmitate

-tocopherol

-tocopherol

-tocopherol

total -carotene

trans--carotene

total cis--carotene

total -carotene

total lycopene

trans-lycopene

total -cryptoxanthin

total -cryptoxanthin

total lutein

total zeaxanthin

total lutein&zeaxanthin

 total coenzyme Q10

ubiquinol (QH2)

ubiquinone (Qox)

phylloquinone (K1)

25-hydroxyvitamin D

Phytoene

Phytofluene

* we prefer g/mL

Were the samples frozen when received? Yes | No

Comments:

Round Robin LXXI: Human Sera

NIST Micronutrients Measurement Quality Assurance Program

Mail: M2QAP

 NIST, Stop 8392

 Gaithersburg, MD 20899-8392

Fax: 301-977-0685

Email: David.Duewer@NIST.gov

Please return results by

16-Apr-2012

A3
Participant #: ________ Date: _____________

This box contains: one vial each of the following five FSV M2QAP sera

Serum Form Reconstitute? Vial/Cap

#382 Liquid frozen No 2 mL clear, forest green cap

#383 Liquid frozen No 2 mL amber, gold cap

#384 Liquid frozen No 2 mL amber, purple cap

#385 Liquid frozen No 2 mL clear, black cap

#386 Liquid frozen No 2 mL amber, blue cap

Please 1) Open the pack immediately

2) Check that it contains all of the above samples

3) Check if the vials are intact

4) Store the sera at -20  ̊C or below until analysis

5) Complete the following information

6) Fax the completed form to us at 301-977-0685

(or email requested information to david.duewer@nist.gov)

1) Date this shipment arrived: ___________________________

2) Are all five sera vials intact? Yes | No

If "No", which one(s) were damaged?

3) Was there any dry-ice left in cooler? Yes | No

4) Did the samples arrive frozen? Yes | No

5) At what temperature are you storing the serum samples? _______  ̊C

6) When do you anticipate analyzing these samples? ________________________

Your prompt return of this information is appreciated.

The M2

QAP Gang

Packing List and Shipment Receipt Confirmation Form

NIST Micronutrients Measurement Quality Assurance Program

Fat-Soluble Vitamins Round Robin LXXI

Mail: M2QAP

 NIST, Stop 8392

 Gaithersburg, MD 20899-8392

Fax: 301-977-0685

Email: David.Duewer@NIST.gov

A4
Appendix B. Final Report for RR71 

The following two pages are the final report as provided to all participants: 

 Cover letter. 

 An information sheet that: 

o describes the contents of the “All-Lab” report, 

o describes the content of the “Individualized” report, 

o describes the nature of the test samples and details their previous distributions, if any, and 

o summarizes aspects of the study that we believe may be of interest to the participants. 

B1
May 10, 2012 

Dear Colleague: 

UNITED STATES DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Gaithersburg, Maryland 20899-

Enclosed is the summary report of the results for round robin LXXI (RR71) of the 2012 NIST 

Micronutrients Measurement Quality Assurance Program (MMQAP) for the fat-soluble vitamins and 

carotenoids in human serum. Included in this report are: 1) a summary of data and measurement 

comparability scores for all laboratories, 2) a detailed graphical analysis of your results; and 3) a 

graphical summary of your measurement comparability. 

Your overall measurement comparability is summarized in the "Score Card" summary, page 6 of the AllLab Report. Combined results rated 1 to 3 are within 1 to 3 standard deviations of the assigned value, 

respectively; those rated 4 are >3 standard deviations from the assigned value. Similar information is 

presented graphically in the "target plots" that are the last page of your Individualized Report. If you 

have concerns regarding your laboratory's performance, please contact us for consultation. 

Samples for the second fat-soluble vitamins and carotenoids in serum interlaboratory exercise (RR72) of 

the 2012 MMQAP will be shipped starting June 25,2012. Please contact us immediately if this 

schedule is problematic for your laboratory. 

If you have questions or concerns regarding this report, please contact David Duewer at 301-975-3935; email: david.duewer@nist.gov or me at 301-975-3120; e-mail: jbthomas@nist.gov; or fax: 301-977-0685. 

Analytical Chemistry Division 

Material Measurement Laboratory 

Enclosures 

cc: L.C. Sander 

David L. Duewer, Ph.D. 

Research Chemometrician 

Analytical Chemistry Division 

Material Measurement Laboratory 

NISI 

B2
The NIST MMQAP Round Robin LXXI (RR71) report consists of: 

Page All-Lab Report 

1-4 A listing of all results and statistics for analytes reported by more than one participant. 

5 A listing of the analytes reported by only one participant and a legend for the list of results 

and statistics. 

6 The text Comparability Summary (“Score Card”) of measurement performance. 

Page Individualized Report 

1 Your values, the number of labs reporting values, and our assigned values. 

2 to 

n 

“Four Plot” summaries of your current and past measurement performance, one page for 

each analyte you report that is also reported by at least eight other participants. 

n+1 The graphical Comparability Summary (target plot) of measurement performance. 

Samples. Five samples were distributed in RR71. 

Serum Description Prior Distributions 

382 Fresh-frozen, native, multi-donor serum prepared in 

2011. This material was designed to have relatively 

high contents of α- and β-carotene. 

New material 

383 Fresh-frozen, native, single-donor serum prepared in 

2011. This material was designed to have low contents 

of α- and β-carotene and lycopene but a high content of 

β-cryptoxanthin. 

New material 

384 Fresh-frozen, native, single-donor serum prepared in 

2011. This material was designed to have rather similar 

analyte contents as the #383 materials but with 

moderate contents of α-carotene and lycopene and a 

low content of β-cryptoxanthin. 

New material 

385 Fresh-frozen, native, multi-donor serum prepared in 

2011. This serum was prepared as a 31:26 mixture of 

the #383:#384 materials. 

New material 

386 Fresh-frozen, native, multi-donor, prepared in 2009. 

This is Level II of SRM 968e. 

#358:RR66-9/09, #364:RR67-3/10, 

#374:RR69-3/11 

Results 

1) SRM 968e Stability. There was no significant change in the median level or measurement variability 

of any measurand in the SRM 968e Level II material. 

2) Analyte additivity. The reported content of serum #385 is well predicted for most analytes by the 

reported contents for its two constituent materials, sera #383 and #384 and the 31:26 mixing ratio. 

However, the -carotene and -cryptoxanthin contents in #384 are slightly higher than expected. 

Since #383 was relatively higher in α-carotene than #384 but lower in β-cryptoxanthin, we’re still 

puzzling over this result. 

B3
Appendix C. All-Lab Report for RR71 

The following six pages are the “All-Lab Report” as provided to all participants, with two 

exceptions: 

 the participant identifiers (Lab) have been altered. 

 the order in which the participant results are listed has been altered. 

The data summary in the “All-Lab Report” has been altered to ensure confidentiality of 

identification codes assigned to laboratories. The only attributed results are those reported by NIST. 

The NIST results are not used in the assessment of the consensus summary results of the study. 

C1
Round Robin LXXI Laboratory Results

Lab 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386

FSV-BG 0.474 0.469 0.475 0.467 0.512 0.052 0.035 0.046 0.032 0.033 11.7 6.75 7.84 7.00 10.15 1.50 1.87 1.96 1.85 1.45

FSV-BA 0.478 0.487 0.484 0.488 0.523 0.072 0.024 0.035 0.029 0.072 11.9 7.16 8.06 7.56 10.67 1.41 1.78 1.83 1.80 1.41FSV-BB 0.432 0.467 0.472 0.465 0.505 0.070 0.007 0.002 0.006 0.024 11.2 7.15 7.70 7.26 10.12 1.39 1.74 1.82 1.77 1.40

FSV-BC 0.472 0.459 0.493 0.490 0.537FSV-BD 0.418 0.450 0.435 0.434 0.480 10.5 7.30 7.20 7.60 10.10

FSV-BE 0.528 0.503 0.509 0.549 0.544 9.7 5.05 6.23 6.05 8.12

FSV-BF 0.450 0.490 0.470 0.470 0.500 11.0 6.40 7.70 7.00 10.10

FSV-BJ 0.472 0.447 0.453 0.449 0.487 12.2 6.89 7.77 7.00 10.20 1.34 1.71 1.80 1.69 1.39

FSV-BK 0.457 0.448 0.453 0.459 0.459 10.2 6.62 7.68 7.05 9.87

FSV-BL 0.460 0.460 0.460 0.460 0.490 10.3 7.75 8.61 8.18 11.63

FSV-BM 0.526 0.453 0.473 0.519 0.567 13.7 8.10 9.29 9.21 12.59

FSV-BN 0.464 0.479 0.482 0.484 0.532 10.0 6.76 7.53 7.15 10.14

FSV-BO 0.384 0.387 0.387 0.387 0.433 10.4 6.46 7.45 6.72 9.95 1.16 1.45 1.50 1.43 1.18

FSV-BP 0.426 0.475 0.501 0.499 0.541 12.7 7.78 8.57 8.18 11.85

FSV-BQ 0.430 0.460 0.440 0.440 0.490 12.0 7.00 8.00 7.00 11.00

FSV-BR 0.480 0.470 0.480 0.460 0.550 13.9 8.50 9.50 8.90 12.60

FSV-BS ≥0.508 ≥0.501 ≥0.573 ≥0.488 ≥0.534 0.508 0.501 0.573 0.488 0.534

FSV-BT 0.477 0.445 0.466 0.466 0.501 11.6 7.39 7.83 7.48 10.33 1.39 1.73 1.84 1.76 1.46

FSV-BU 0.476 0.462 0.340 0.518 0.493 11.0 7.86 8.26 7.98 11.04 1.18 2.07 1.70 1.78 1.46

FSV-BV 0.511 0.575 0.571 0.584 0.578 12.9 7.70 8.85 8.37 11.60 1.47 1.95 2.02 1.95 1.49

FSV-BW 0.450 0.430 0.460 0.450 0.480 0.071 0.019 0.018 0.014 0.035 11.7 7.19 8.46 7.75 11.04 1.34 1.76 1.80 1.85 1.46

FSV-CC 0.452 0.428 0.452 0.473 0.503 0.444 0.425 0.444 0.466 0.496 10.8 6.80 8.15 7.51 10.45FSV-CD 0.429 0.473 0.503 0.511 0.539 0.076 nq 0.018 nq 0.027 11.0 7.81 9.46 8.62 11.52 1.36 1.90 2.14 2.00 1.65

FSV-CE 0.380 0.430 0.510 0.480 0.480 13.1 7.00 5.20 5.84 11.10

FSV-CG 0.518 0.507 0.505 0.515 0.539 11.6 6.98 7.88 7.50 10.00 1.52 1.57 1.67 1.65 1.36

FSV-CI 0.453 0.450 0.451 0.477 0.515 0.056 0.011 0.019 0.014 0.034 10.5 6.66 7.58 6.77 9.59 1.30 1.77 1.87 1.74 1.43

FSV-CZ 0.390 0.310 0.310 0.390 0.440 11.3 7.53 8.55 8.02 11.16 1.09 1.52 1.64 1.57 1.18

FSV-DD 0.420 0.420 0.430 0.460 0.470

FSV-DV 0.502 0.524 0.516 0.508 0.551 10.5 6.80 8.00 7.10 9.70

FSV-EE

FSV-EZ 0.486 0.413 0.412 0.426 0.452 0.060 ≤0.02 ≤0.02 ≤0.02 0.020 11.2 6.50 7.71 7.53 10.25 1.30 1.58 1.69 1.75 1.35

FSV-FK 0.449 0.449 0.460 0.489 0.500 12.5 7.60 8.50 8.00 10.90

FSV-FZ 0.465 0.499 0.494 0.481 0.548 11.9 7.81 8.59 7.63 11.56 1.50 1.98 2.04 1.78 1.59

N 31 31 31 31 31 2 2 2 2 2 7 5 6 5 7 29 29 29 29 29 15 15 15 15 15

Min 0.380 0.310 0.310 0.387 0.433 0.444 0.425 0.444 0.466 0.496 0.052 0.007 0.002 0.006 0.020 9.7 5.05 5.20 5.84 8.12 1.09 1.45 1.50 1.43 1.18

Median 0.460 0.460 0.470 0.473 0.503 0.476 0.463 0.509 0.477 0.515 0.070 0.019 0.019 0.014 0.033 11.3 7.15 8.00 7.51 10.45 1.36 1.76 1.82 1.77 1.43

Max 0.528 0.575 0.571 0.584 0.578 0.508 0.501 0.573 0.488 0.534 0.076 0.035 0.046 0.032 0.072 13.9 8.50 9.50 9.21 12.60 1.52 2.07 2.14 2.00 1.65

SD 0.030 0.022 0.034 0.024 0.043 0.009 0.012 0.012 0.012 0.009 1.2 0.67 0.68 0.76 0.86 0.09 0.21 0.19 0.11 0.06

CV 6 5 7 5 8 12 62 66 86 26 11 9 9 10 8 7 12 11 6 4

Npast 32 7 8 33 19

Medianpast 0.510 0.481 0.024 10.25 1.40

SDpast 0.044 0.050 0.009 0.76 0.13

NIST 0.476 0.478 0.474 0.479 0.499 11.3 7.37 7.60 7.31 10.36 1.41 1.78 1.80 1.84 1.42

NAV 0.468 0.469 0.472 0.476 0.501 0.070 0.019 0.019 0.014 0.033 11.3 7.26 7.80 7.41 10.40 1.39 1.77 1.81 1.81 1.42

NAU 0.039 0.039 0.038 0.038 0.043 0.020 0.012 0.012 0.012 0.013 1.2 0.69 0.74 0.77 0.86 0.16 0.21 0.19 0.20 0.16

Total Retinol, μg/mL trans-Retinol, μg/mL Retinyl Palmitate, μg/mL α-Tocopherol, μg/mL γ/β-Tocopherol, μg/mL

All Lab Report Page 1 / 6

C2
Round Robin LXXI Laboratory Results

Lab

FSV-BG

FSV-BAFSV-BB

FSV-BCFSV-BD

FSV-BE

FSV-BF

FSV-BJ

FSV-BK

FSV-BL

FSV-BM

FSV-BN

FSV-BO

FSV-BP

FSV-BQ

FSV-BR

FSV-BS

FSV-BT

FSV-BU

FSV-BV

FSV-BW

FSV-CCFSV-CD

FSV-CE

FSV-CG

FSV-CI

FSV-CZ

FSV-DD

FSV-DV

FSV-EE

FSV-EZFSV-FK

FSV-FZ

N

Min

Median

Max

SDCV

Npast

Medianpast

SDpast

NIST

NAV

NAU

382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386

0.65 0.045 0.058 0.052 0.247 0.34 0.014 0.036 0.024 0.033

0.098 0.068 0.080 0.074 0.055 0.76 0.049 0.060 0.058 0.284 0.72 0.046 0.056 0.054 0.265 0.040 0.003 0.003 0.004 0.019 0.42 0.011 0.037 0.023 0.0360.064 0.057 0.058 0.059 0.043 0.89 0.041 0.087 0.056 0.192 0.55 0.032 0.052 0.038 0.166 0.036 0.002 0.004 0.002 0.008 0.31 0.007 0.032 0.016 0.018

0.77 0.052 0.064 0.068 0.2410.59 0.027 0.039 0.027 0.2560.53 0.037 0.027 0.036 0.183 0.46 nq 0.026 0.028 nq0.57 0.044 0.061 0.051 0.250 0.38 0.012 0.045 0.027 0.047

0.53 0.047 0.065 0.059 0.239 0.28 0.009 0.038 0.025 0.0310.52 0.089 0.121 0.160 0.247 0.32 0.023 0.017 0.024 0.057

≥0.486 ≥0.07 ≥0.074 ≥0.084 ≥0.201 0.49 0.070 0.074 0.084 0.201 0.24 0.022 0.036 0.032 0.036

0.011 0.010 0.010 0.010 0.011 0.72 0.050 0.078 0.064 0.263 0.63 0.044 0.068 0.056 0.234 0.033 0.003 0.004 0.003 0.011 0.22 0.010 0.032 0.020 0.028

0.67 0.054 0.065 0.057 0.217 0.43 0.015 0.046 0.030 0.027

0.72 0.049 0.064 0.055 0.265 0.63 0.012 0.050 0.029 0.0360.57 0.032 0.046 0.046 0.226 0.44 0.011 0.035 0.023 0.0220.44 0.144 0.153 0.151 0.253 0.28 0.004 0.029 0.019 0.0190.70 0.040 0.020 0.030 0.220

0.593 0.503 0.302 0.435 0.343 0.73 0.047 0.062 0.055 0.242 0.67 0.043 0.056 0.052 0.220 0.053 nq nq nq 0.019 0.51 0.016 0.045 0.032 0.040

0.76 0.058 0.066 0.055 0.297 0.46 0.013 0.041 0.027 0.039

0.56 0.040 0.050 0.050 0.1900.60 ≤0.059 ≤0.059 ≤0.059 0.206

4 4 4 4 4 19 18 18 18 19 5 5 5 5 5 4 3 3 3 4 15 14 15 15 14

0.011 0.010 0.010 0.010 0.011 0.44 0.027 0.020 0.027 0.183 0.49 0.032 0.052 0.038 0.166 0.033 0.002 0.003 0.002 0.008 0.22 0.004 0.017 0.016 0.0180.081 0.063 0.069 0.067 0.049 0.65 0.047 0.063 0.055 0.242 0.63 0.044 0.056 0.054 0.220 0.038 0.003 0.004 0.003 0.015 0.38 0.012 0.036 0.025 0.0340.593 0.503 0.302 0.435 0.343 0.89 0.144 0.153 0.160 0.297 0.72 0.070 0.074 0.084 0.265 0.053 0.003 0.004 0.004 0.019 0.63 0.023 0.050 0.032 0.0570.065 0.043 0.052 0.048 0.032 0.12 0.009 0.013 0.007 0.031 0.13 0.004 0.007 0.004 0.029 0.005 0.006 0.12 0.004 0.007 0.004 0.009

80 68 75 72 66 19 20 21 12 13 20 8 12 7 13 14 38 30 34 20 18 26

5 22 8 618

0.081 0.239 0.215 0.013 0.031

0.020 0.032 0.025 0.003 0.012

0.68 0.053 0.057 0.061 0.251 0.37 0.010 0.033 0.022 0.028

0.081 0.063 0.069 0.067 0.049 0.67 0.050 0.060 0.058 0.246 0.63 0.044 0.056 0.054 0.220 0.038 0.003 0.004 0.003 0.015 0.38 0.011 0.035 0.024 0.031

0.12 0.011 0.014 0.012 0.037 0.13 0.009 0.009 0.009 0.029 0.12 0.005 0.012 0.009 0.012

δ-Tocopherol, μg/mL Total β-Carotene, μg/mL trans-β-Carotene, μg/mL Total cis-β-Carotene, μg/mL Total α-Carotene, μg/mL

All Lab Report Page 2 / 6

C3
Round Robin LXXI Laboratory Results

Lab

FSV-BG

FSV-BAFSV-BB

FSV-BCFSV-BD

FSV-BE

FSV-BF

FSV-BJ

FSV-BK

FSV-BL

FSV-BM

FSV-BN

FSV-BO

FSV-BP

FSV-BQ

FSV-BR

FSV-BS

FSV-BT

FSV-BU

FSV-BV

FSV-BW

FSV-CCFSV-CD

FSV-CE

FSV-CG

FSV-CI

FSV-CZ

FSV-DD

FSV-DV

FSV-EE

FSV-EZFSV-FK

FSV-FZ

N

Min

Median

Max

SDCV

Npast

Medianpast

SDpast

NIST

NAV

NAU

382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386

0.287 0.180 0.329 0.245 0.61 0.146 0.092 0.173 0.128 0.328 0.067 0.203 0.027 0.116 0.0590.251 0.151 0.246 0.220 0.52 0.131 0.074 0.128 0.110 0.282 0.083 0.202 0.028 0.131 0.084 0.029 0.032 0.016 0.027 0.0460.247 0.132 0.264 0.192 0.43 0.118 0.070 0.134 0.098 0.253 0.061 0.146 0.022 0.090 0.050 0.018 0.018 0.011 0.015 0.0190.278 0.135 0.250 0.178 0.55 0.064 0.107 nq 0.061 nq

0.062 0.178 0.029 0.112 0.059

0.180 0.153 0.267 0.237 0.46 0.044 0.148 0.012 0.085 0.0340.389 0.257 0.472 0.432 1.22 0.065 0.138 0.034 0.010 0.0730.101 0.065 0.114 0.108 0.27 0.028 0.065 0.108 0.076 0.180 0.065 0.161 0.053 0.129 0.0750.273 0.182 0.338 0.260 0.60 0.132 0.099 0.189 0.146 0.356 0.043 0.081 0.018 0.054 0.038 0.013 0.010 0.011 0.010 0.0170.283 0.171 0.327 0.232 0.56 0.062 0.164 0.016 0.083 0.0430.347 0.195 0.368 0.281 0.68 0.068 0.217 0.019 0.120 0.0520.242 0.171 0.325 0.224 0.65 0.057 0.147 0.017 0.099 0.0500.337 0.248 0.344 0.306 0.63 0.104 0.237 0.039 0.156 0.095 0.029 0.035 0.021 0.028 0.0410.369 0.209 0.340 0.275 0.59 0.165 0.096 0.162 0.128 0.298 0.111 0.208 0.038 0.130 0.079

13 13 13 13 13 6 6 6 6 6 14 14 13 14 13 4 4 4 4 4

0.101 0.065 0.114 0.108 0.27 0.028 0.065 0.108 0.076 0.180 0.043 0.081 0.012 0.010 0.034 0.013 0.010 0.011 0.010 0.0170.278 0.171 0.327 0.237 0.59 0.132 0.083 0.148 0.119 0.290 0.065 0.163 0.027 0.106 0.059 0.023 0.025 0.013 0.021 0.0300.389 0.257 0.472 0.432 1.22 0.165 0.099 0.189 0.146 0.356 0.111 0.237 0.053 0.156 0.095 0.029 0.035 0.021 0.028 0.0460.053 0.036 0.060 0.056 0.08 0.021 0.019 0.033 0.022 0.055 0.005 0.048 0.014 0.034 0.023 0.008 0.013 0.004 0.010 0.018

19 21 18 24 14 16 23 22 19 19 8 29 52 32 40 36 50 27 47 59

17 8 17 4

0.62 0.294 0.052 0.0250.09 0.046 0.014 0.007

0.282 0.170 0.331 0.253 0.51 0.069 0.205 0.025 0.095 0.0450.280 0.171 0.329 0.245 0.55 0.132 0.083 0.148 0.119 0.290 0.067 0.184 0.026 0.100 0.052 0.023 0.025 0.013 0.021 0.0300.064 0.043 0.073 0.057 0.13 0.023 0.019 0.033 0.022 0.055 0.016 0.056 0.014 0.035 0.025

Total Lycopene, μg/mL trans-Lycopene, μg/mL Total β-Cryptoxanthin, μg/mL Total α-Cryptoxanthin, μg/mL

All Lab Report Page 3 / 6

C4
Round Robin LXXI Laboratory Results

Lab

FSV-BG

FSV-BAFSV-BB

FSV-BCFSV-BD

FSV-BE

FSV-BF

FSV-BJ

FSV-BK

FSV-BL

FSV-BM

FSV-BN

FSV-BO

FSV-BP

FSV-BQ

FSV-BR

FSV-BS

FSV-BT

FSV-BU

FSV-BV

FSV-BW

FSV-CCFSV-CD

FSV-CE

FSV-CG

FSV-CI

FSV-CZ

FSV-DD

FSV-DV

FSV-EE

FSV-EZFSV-FK

FSV-FZ

N

Min

Median

Max

SDCV

Npast

Medianpast

SDpast

NIST

NAV

NAU

382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386 382 383 384 385 386

0.162 0.115 0.112 0.110 0.1320.207 0.164 0.134 0.154 0.186

0.171 0.127 0.134 0.128 0.136 0.053 0.086 0.048 0.068 0.088 0.224 0.213 0.182 0.196 0.224

0.670 1.06 0.920 0.970 0.940 3.955 0.267 0.409 0.330 0.879

0.138 0.082 0.068 0.069 0.089 0.752 1.00 0.884 0.936 0.959

0.154 0.187 0.117 0.139 0.139

0.135 0.111 0.084 0.102 0.110 0.039 0.014 0.026 0.020 0.021 0.175 0.126 0.110 0.122 0.131 0.732 1.11 0.961 1.014 1.064

0.289 0.136 0.184 0.196 0.1860.074 0.075 0.057 0.084 0.0630.117 0.088 0.075 0.086 0.089 0.655 1.08 0.965 1.051 1.0120.158 0.110 0.092 0.096 0.116 0.810 1.12 0.965 1.010 0.9750.152 0.145 0.097 0.117 0.1340.109 0.078 0.065 0.084 0.078 0.769 0.91 0.722 0.993 0.8920.173 0.140 0.103 0.138 0.1440.225 0.176 0.139 0.163 0.171

0.108 0.073 0.063 0.069 0.078 0.011 0.035 0.008 0.024 0.026 0.119 0.108 0.071 0.093 0.104 0.690 1.06 0.920 0.990 0.930 1.862 0.099 0.190 0.129 0.351

0.780 1.20 1.160 1.230 1.1700.677 1.13 0.955 0.968 0.941

4 4 4 4 4 3 3 3 3 3 14 14 14 14 14 9 9 9 9 9 2 2 2 2 2

0.108 0.073 0.063 0.069 0.078 0.011 0.014 0.008 0.020 0.021 0.074 0.075 0.057 0.084 0.063 0.655 0.91 0.722 0.936 0.892 1.862 0.099 0.190 0.129 0.3510.137 0.097 0.076 0.086 0.100 0.039 0.035 0.026 0.024 0.026 0.160 0.131 0.107 0.120 0.133 0.732 1.08 0.955 0.993 0.959 2.909 0.183 0.300 0.230 0.6150.171 0.127 0.134 0.128 0.136 0.053 0.086 0.048 0.068 0.088 0.289 0.213 0.184 0.196 0.224 0.810 1.20 1.160 1.230 1.170 3.955 0.267 0.409 0.330 0.8790.022 0.028 0.016 0.024 0.024 0.062 0.041 0.044 0.044 0.050 0.071 0.06 0.052 0.034 0.043

16 29 20 29 24 39 32 41 37 37 10 5 5 3 4

9 8 18 8

0.087 0.030 0.125 0.9600.018 0.013 0.029 0.072

nq 0.110 0.075 0.084 0.102 0.042 0.030 0.045 0.029 0.032 nq 0.140 0.120 0.113 0.134

0.137 0.103 0.075 0.085 0.101 0.040 0.032 0.036 0.027 0.029 0.160 0.136 0.113 0.116 0.134 0.732 1.08 0.955 0.993 0.959

0.030 0.016 0.024 0.024 0.011 0.010 0.016 0.008 0.009 0.062 0.042 0.045 0.045 0.050 0.073 0.11 0.096 0.099 0.096

Phylloquinone (K1), ng/mL Total Lutein&Zeaxanthin, μg/mL Coenzyme Q10, μg/mL Total Lutein, μg/mL Total Zeaxanthin, μg/mL

All Lab Report Page 4 / 6

C5
Round Robin LXXI Laboratory Results

Analytes Reported By One Laboratory

Analyte Lab 382 383 384 385 386

25-hydroxyvitamin D, μg/mL FSV-BN 0.0153 0.0046 0.0037 0.0027 0.0104

Phytofluene, μg/mL FSV-BS 0.093 0.101 0.104 0.094 0.132

Phytoene, μg/mL FSV-BS 0.108 nd nd nd 0.122

Term Legend

N Number of (non-NIST) quantitative values reported for this analyte

Min Minimum (non-NIST) quantitative value reported

Median Median (non-NIST) quantitative value reported

Max Maximum (non-NIST) quantitative value reported

SD Adjusted median absolute deviation from the median of the non-NIST results

CV Coefficient of Variation for (non-NIST) results: 100*SD/Median

Npast Mean of N(s) from past RR(s)

Medianpast Mean of Median(s) from past RR(s)

SDpast Pooled SD from past RR(s)

NIST Mean of NIST results

NAV NIST Assigned Value

 = (Median + NIST)/2 for analytes reported by NIST

 = Median for analytes reported by ≥ 5 labs but not NIST

NAU NIST Assigned Uncertainty: √(S2 + Sbtw2

)

 S is the maximum of (0.05*NAV, SD, SDpast, eSD) and Sbtw is the standard

 deviation between Median and NIST. The expected long-term SD, eSD,

 is defined in: Duewer et al., Anal Chem 1997;69(7):1406-1413.

nd Not detected (i.e., no detectable peak for analyte)

nq Detected but not quantitatively determined

≤x Concentration at or below the limit of quantification, x

≥x Concentration greater than or equal to x

italics Not explicitly reported but calculated by NIST from reported values

All Lab Report

C6

Page 5 / 6
Round Robin LXXI Laboratory Results

Lab TR aT g/bT bC aC TLy TbX L&Z Label Definition

FSV-BG 1 1 1 1 1 1 1 1 Lab Participant code

FSV-BA 1 1 1 1 1 1 1 1 TR Total Retinol

FSV-BB 1 1 1 2 1 1 1 2 aT -Tocopherol

FSV-BC 1 g/bT -Tocopherol

FSV-BD 1 1 bC Total -Carotene

FSV-BE 2 3 1 aC Total -Carotene

FSV-BF 1 1 2 TLy Total Lycopene

FSV-BJ 1 1 1 2 1 1 2 TbX Total -Cryptoxanthin

FSV-BK 1 1 L&Z Total Lutein & Zeaxanthin

FSV-BL 1 2

FSV-BM 2 2 n number of participants providing quantitative data

FSV-BN 1 1 1 1 1 1 % 1 Percent of CS = 1 (within 1 SD of medians)

FSV-BO 2 1 2 1 1 1 1 1 % 2 Percent of CS = 2 (within 2 SD of medians)

FSV-BP 1 2 4 2 4 2 2 % 3 Percent of CS = 3 (within 3 SD of medians)

FSV-BQ 1 1 % 4 Percent of CS = 4 (3 or more SD from medians)

FSV-BR 1 3

FSV-BS 2 2 2 3 1 2

FSV-BT 1 1 1 1 1 1 2 1

FSV-BU 2 1 1 1 1 1 1 1

FSV-BV 3 2 1 1 2 1 1 1

FSV-BW 1 1 1 1 1 1 1 2

FSV-CC 1 1

FSV-CD 1 2 2 4 2 2 2 1

FSV-CE 2 3 2

FSV-CG 2 1 1 1 1 1 2 1

FSV-CI 1 1 1 1 1 1

FSV-CZ 3 1 2 1

FSV-DD 1

FSV-DV 2 1

FSV-EZ 2 1 1 1

FSV-FK 1 1

FSV-FZ 1 1 1

NIST 1 1 1 1 1 1 1 1

n 33 30 16 21 16 14 15 15

TR aT g/bT bC aC TLy TbX L&Z

% 1 67 73 81 67 75 79 67 73

% 2 27 17 19 24 25 7 33 27

% 3 6 10 0 0 0 7 0 0

% 4 0 0 0 10 0 7 0 0

Comparability Summary

“Comparability Score” 

The Comparability Score (CS) summarizes your measurement 

performance for a given analyte relative to the consensus 

medians in this study. CS is the average distance (in units of 

standard deviation) of your measurement performance 

characteristics from the consensus performance. CS is 

calculated when the number of quantitative values you reported, 

Nyou, is at least two and at least six participants reported 

quantitative values for the analyte. 

We define CS as follows: 

CS = 



 



 



 



  22 MINIMUM 4,INTEGER APC1

C = Concordance = 

you

N

1i i

i i

N

NAU

You Median you





AP = Apparent Precision = 1N

NAU

You Median

you

N

1i

2

i

i i

you

















  

NAU = NIST Assigned Uncertainty 

For further details, please see 

Duewer DL, Kline MC, Sharpless KE, Brown Thomas J, Gary 

KT. Micronutrients Measurement Quality Assurance 

Program: Helping participants use interlaboratory comparison 

exercise results to improve their long-term measurement 

performance. Anal Chem 1999;71(9):1870-8.

All Lab Report

C7

Page 6 / 6
Appendix D. Representative Individualized Report for RR71 

Each participant in RR71 received an “Individualized Report” reflecting their reported results. Each 

report included a detailed analysis for analytes that were assayed by at least five participants. The 

following analytes met this criterion in RR71: 

 Total Retinol 

 Retinyl Palmitate 

 Total α-Carotene 

 α-Tocopherol 

 γ/β-Tocopherol 

 Total β-Cryptoxanthin 

 Total β-Carotene 

 Trans-β-Carotene 

 Total Lutein & Zeaxanthin 

 Total Lycopene 

 Trans-Lycopene 

 Coenzyme Q10 

The following ten pages are the “Individualized Report” for the analytes evaluated at NIST. 

D1
 Set 34 of 34

Individualized Round Robin LXXI Report: NIST1

Summary

Serum 382 Serum 383 Serum 384 Serum 385 Serum 386

Analyte You NAV n You NAV n You NAV n You NAV n You NAV n

Total Retinol 0.476 0.469 31 0.478 0.469 31 0.474 0.471 31 0.479 0.474 31 0.499 0.500 31

α-Tocopherol 11.31 11.45 29 7.37 7.26 29 7.60 7.77 29 7.31 7.41 29 10.36 10.43 29

γ/β-Tocopherol 1.413 1.389 15 1.783 1.767 15 1.803 1.807 15 1.839 1.804 15 1.416 1.419 15

Total β-Carotene 0.683 0.675 19 0.053 0.050 18 0.057 0.060 18 0.061 0.058 18 0.251 0.246 19Total α-Carotene 0.373 0.395 15 0.010 0.011 14 0.033 0.035 15 0.022 0.024 15 0.028 0.031 14

Total Lycopene 0.282 0.278 13 0.170 0.171 13 0.331 0.329 13 0.253 0.244 13 0.511 0.543 13

Total β-Cryptoxanthin 0.069 0.067 14 0.205 0.180 14 0.025 0.023 13 0.095 0.095 14 0.045 0.048 13

Total Lutein nq 0.137 4 0.110 0.103 4 0.075 0.075 4 0.084 0.085 4 0.102 0.101 4

Total Zeaxanthin 0.042 0.040 3 0.030 0.032 3 0.045 0.036 3 0.029 0.027 3 0.032 0.029 3

Total Lutein&Zeaxanthin nq 0.160 14 0.140 0.131 14 0.120 0.112 14 0.113 0.113 14 0.134 0.133 14

You : Your reported values for the listed analytes (micrograms/milliliter)

NAV : NIST Assigned Values, here equal to this RR's median

n : Number of non-NIST laboratories reporting quantitative values for this analyte in this serum

nq : Detected, but not quantitatively determined

Please check our records against your records. Send corrections and/or updates to...

Micronutrients Measurement Quality Assurance ProgramNational Institute of Standards and Technology Tel: (301) 975-3935

100 Bureau Drive Stop 8392 Fax: (301) 977-0685Gaithersburg, MD 20899-8392 USA Email: david.duewer@nist.gov

Individualized Report ILR_RR71_NIST1.XLS, Page 1 / 10

D2
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total Retinol, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 2 / 10

D3
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

α-Tocopherol, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 3 / 10

D4
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

γ/β-Tocopherol, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 4 / 10

D5
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total β-Carotene, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 5 / 10

D6
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total α-Carotene, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 6 / 10

D7
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total Lycopene, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 7 / 10

D8
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total β-Cryptoxanthin, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 8/ 10

D9
 Set 34 of 34

Individualized RR LXXI Report: NIST1

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Serum Comments History

#382 Fresh-frozen, native, multi-donor New

#383 Fresh-frozen, native, single-donor New

#384 Fresh-frozen, native, single-donor New

#385 Mixture of (310 mL #383) and (260 mL #384) New

#386 Fresh-frozen, native, multi-donor: SRM 968e II 66#358, 67#364, 69#374

Total Lutein&Zeaxanthin, μg/mL

382383385384358364374386

[Analyte], μg/mL Apparent Precision, SD

Concordance, SD

Median [Analyte], μg/mL

Your [Analyte], μg/mL

Long-term Precision, SD

Apparent Precision, SD

You, this RR

 You, past RRs Others, this RR

Expectation

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

You, ≥x, this RR

You, ≥x, past RRs

Individualized Report ILR_RR71_NIST1.XLS, Page 9 / 10

D10
 Set 34 of 34

Total Retinol α-Tocopherol Total β-Carotene Total Lycopene

Retinyl palmitate γ/β-Tocopherol trans-β-Carotene trans-Lycopene

Total α-Carotene Total β-Cryptoxanthin Total Lutein&Zeaxanthin Coenzyme Q10

Individualized Round Robin LXXI Report: NIST1

Graphical Comparability Summary

Individualized Report ILR_RR71_NIST1.XLS, Page 10 / 10

D11
Appendix E. Shipping Package Inserts for RR36 

The following five items were included in each package shipped to an RR36 participant: 

 Cover letter 

 Protocol for Preparation and Analysis of the Ascorbic Acid Solid Control Material 

 Preparation and Validation of Ascorbic Acid Solid Control Material Datasheet 

 Analysis of Control Materials and Test Samples Datasheet 

 Packing List and Shipment Receipt Confirmation Form 

The cover letter, preparation protocol, and the two datasheets were enclosed in a sealed waterproof 

bag along with the samples themselves. The packing list was placed at the top of the shipping box, 

between the cardboard covering and the foam insulation. 

E1
January 2, 2012 

Dear Colleague: 

UNITED STATES DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Gaithersburg, Maryland 20899-

The samples within this package constitute Vitamin C Round Robin 36 (RR36) ofthe 2012 Micronutrients 

Measurement Quality Assurance Program. RR36 consists offour vials offrozen serum test samples (#361, #362 

#363, and #364), one vial of frozen conh·ol serum (CS #2), and one vial of ascorbic acid solid conh·ol material 

(Control). Please follow the attached protocols when you prepare and analyze these samples. If you cannot 

prepare the solid control solutions gravimetrically, please prepare equivalent solutions volumetrically and report 

the exact volumes used. (Routine 0.5 g gravimetric measurements are generally 10-fold more accurate than routine 

0.5 mL volumetric measurements.) 

Please use the control serum to validate the performance of your measurement system before you analyze the test 

samples. The target value for CS #2 is 28.05 J.lmoi/L of sample; the ::::95% confidence interval for the target value 

is 27.56 to f8.54 J.lmoi/L of sample. 

Please be aware that sample contact with any oxidant-contaminated surface (vials, glassware, etc.) may degrade 

your measurement system's performance (SA Margolis and E Park, "Stability of Ascorbic Acid in Solutions in 

Autosampler Vials", Clinical Chemishy 2001, 47(8), 1463-1464). You should suspect such degradation if you · 

observe unusually large variation in replicate analyses. 

Please report your results (using the attached form) for RR36 by e-mail to david.duewer@nist.gov or fax to . 

301-977-0685 by April16, 2012. If you have questions or comments regarding this study, please call me at 

(301) 975-3120 or e-mail me iJbthomas@nist.gov. 

~ncerely, i ~ ]U U i 'OJYilGj 

anice Brown Thomas 

ogram Coordinator/Research Chemist 

alytical Chemistry Division 

Chemical Science and Technology Laboratory 

Enclosures: Protocols, Preparation and Analysis of Control Materials and Analysis of Test Samples 

RR36 Report Form for Ascorbic Acid Solid Control Material Preparation 

RR36 Report Form for Control Material and Test Sample Analyses 

E2

NISI 
Micronutrient Measurement Quality Assurance Program for 

Vitamin C 

Please Read Through Completely BEFORE Analyzing Samples

Protocol for Preparation and Analysis of the Ascorbic Acid Solid Control Material

The ascorbic acid solid control material (in the amber vial) should be prepared and used in the 

following manner: 

1) Prepare at least 500 mL of 5% mass fraction metaphosphoric acid (MPA) in distilled water. This 

solution will be referred to as the “Diluent” below. 

2) Weigh 0.20 to 0.22 g of the ascorbic acid solid control material to 0.0001 g (if possible), dissolve 

it in the Diluent in a 100 mL volumetric flask, and dilute with the Diluent to the 100 mL mark. 

Weigh the amount of Diluent added to 0.1 g. Record the weights. The resulting material will be 

referred to as the “Stock Solution” below. 

3) Prepare three dilute solutions of the Stock Solution as follows: 

Dilute Solution 1: Weigh 0.500 mL of the Stock Solution to 0.0001 g into a 100 mL volumetric 

flask; dilute with Diluent to the 100 mL mark. Record the weight. 

Dilute Solution 2: Weigh 0.250 mL of the Stock Solution to 0.0001 g into a 100 mL volumetric 

flask; dilute with Diluent to the 100 mL mark. Record the weight. 

Dilute Solution 3: Weigh 0.125 mL of the Stock Solution to 0.0001 g into a 100 mL volumetric 

flask; dilute with Diluent to the 100 mL mark. Record the weight. 

4) Calculate and record the total ascorbic acid concentrations, [TAA], in these Dilute Solutions. 

If you follow the above gravimetric preparation directions, the [TAA] in μmol/L is calculated: 

     

  Solution Stock in AA g   Solution Stock in Diluent g

Solution Dilute in Solution Stock g Solution Stock in AA g Lmol/g 56785 [TAA]DS



    

For example, if you prepared the Stock Solution with 0.2000 g of solid ascorbic acid and 103.0 g 

of Diluent, then 0.5 mL of the Stock Solution should weigh (0.2+103)/200 = 0.52 g and 

[TAA]DS1 = (0.52 g)(0.2 g)·(56785 μmol/g·L)/(0.2 + 103 g) = 57.2 μmol/L. Likewise, 0.25 mL 

of the Stock Solution should weigh 0.26 g and [TAA]DS2 = 29.4 μmol/L and 0.125 mL should 

weigh 0.13 g and [TAA]DS3 = 14.2 μmol/L. 

5) Measure the ultraviolet absorbance spectrum of Dilute Solution 1 against the Diluent as the 

blank using paired 1 cm path length cuvettes. Record the absorbance at (242, 243, 244, & 245)

nm. Record the maximum absorbance (Amax) within this region. Record the wavelength (λmax) 

at which this maximum occurs. 

The extinction coefficient (E1%) of ascorbic acid at λmax (using a cell with a 1 cm path length) of 

Dilute Solution #1 can be calculated: 

E3
     

  Solution Stock in AA g1 Solution Dilute in Solution Stock g 

Solution Stock in Diluent g Solution Stock in AA gA )

cmg

dL (E1% max



   

If your spectrophotometer is properly calibrated, λmax should be between 243 and 244 nm and 

E1% should be 550 ± 30 dL/g·cm. If they are not, you should recalibrate the wavelength and/or 

absorbance axes of your spectrophotometer and repeat the measurements. 

6) Measure and record the concentration of total ascorbic acid in all three dilute solutions and in the 

5% MPA Diluent in duplicate using exactly the same method that you will use for the serum 

control materials and test samples, including any enzymatic treatment. We recommend that you 

analyze these solutions in the following order: Diluent, Dilute Solution 1, Dilute Solution 2, 

Dilute Solution 3, Dilute Solution 3, Dilute Solution 2, Dilute Solution 1, Diluent. 

a) Compare the values of the duplicate measurements. Are you satisfied that your measurement 

precision is adequate?

b) Compare the measured with the calculated [TAA] values. This is most conveniently done by 

plotting the measured values on the y-axis of a scatterplot against the calculated values on 

the x-axis. The line through the four {calculated, measured} data pairs should go through the 

origin with a slope of 1.0. Are you satisfied with the agreement between the measured and 

calculated values?

Do not analyze the serum control materials or test samples until you are satisfied that your 

system is performing properly! 

7) Once you have confirmed that your system is properly calibrated, analyze the serum control 

CS #2 (see protocol below). The target values for this materials is 28.1 ±1.0 μmol/L of sample.

If your measured values are not close to this value, please review your sample preparation 

procedure and whether you followed exactly the same measurement protocol the solutions 

prepared from the solid control material as you used for these serum controls. If the protocols 

differ, please repeat from Step 6 using the proper protocol. If the proper protocol was used, your 

measurement system may not be suitable for MPA-preserved samples; please contact us at 301-

975-3120 or jbthomas@NIST.gov. 

Do not analyze the test samples until you are satisfied that your system is performing properly 

and is suitable for the analysis of MPA-preserved serum! 

Protocol for Analysis of the Serum Control Materials and Test Samples 

The serum control material and test samples are in sealed ampoules. They were prepared by adding 

equal volumes of 10% MPA to spiked human serum. We have checked the samples for stability and 

homogeneity. Only the total ascorbic acid is stable. While these samples contain some 

dehydroascorbic acid, its content is variable. Therefore, only total ascorbic acid should be reported. 

 The serum control material and test samples should be defrosted by warming at 20 °C for not more 

than 10 min otherwise some irreversible degradation may occur. 

Each serum test sample contains between 0.0 and 80.0 μmol of total ascorbic acid/L of solution. 

The total ascorbic acid in each ampoule should be measured in duplicate. Please report your results 

in μmol/(L of the sample solution) rather than μmol/(L of serum NIST used to prepare the sample). 

E4
Participant #: Date: 

Please return by April 16, 2012

MMQAP Fax: 301-977-0685 

100 Bureau Drive, Stop 8392 Email: david.duewer@nist.gov 

Gaithersburg, MD 20899-8392 

Vitamin C Round Robin 36 

NIST Micronutrient Measurement Quality Assurance Program

Preparation and Validation of Ascorbic Acid Solid Control Material 

STOCK SOLUTION

Mass of ascorbic acid in the Stock Solution..................................................__________ g 

Mass of 5% MPA Diluent added to the 100 mL volumetric flask ................__________ g 

DILUTE SOLUTION 1 

Mass of added stock solution (0.5 mL)..........................................................__________ g 

Mass of 5% MPA Diluent added to the 100 mL volumetric flask ................__________ g 

Absorbance of Dilute Solution 1 at 242 nm ..................................................__________ AU 

Absorbance of Dilute Solution 1 at 243 nm ..................................................__________ AU 

Absorbance of Dilute Solution 1 at 244 nm ..................................................__________ AU 

Absorbance of Dilute Solution 1 at 245 nm ..................................................__________ AU 

Absorbance of Dilute Solution absorbance maximum ..................................__________ AU 

Wavelength of maximum absorbance............................................................__________ nm 

Calculated E1% ...............................................................................................__________ dL/g·cm 

Calculated [TAA]DS1......................................................................................__________ μmol/L 

DILUTE SOLUTION 2 

Mass of added stock solution (0.25 mL)........................................................__________ g 

Mass of 5% MPA Diluent added to the 100 mL volumetric flask ................__________ g 

Calculated [TAA]DS2......................................................................................__________ μmol/L 

DILUTE SOLUTION 3 

Mass of added stock solution (0.125 mL)......................................................__________ g 

Mass of 5% MPA Diluent added to the 100 mL volumetric flask ................__________ g 

Calculated [TAA]DS3......................................................................................__________ μmol/L 

E5
Participant #: Date: 

Please return by April 16, 2012

MMQAP Fax: 301-977-0685 

100 Bureau Drive, Stop 8392 Email: david.duewer@nist.gov 

Gaithersburg, MD 20899-8392 

Vitamin C Round Robin 36 

NIST Micronutrient Measurement Quality Assurance Program

Analysis of Control Materials and Test Samples 

Sample Replicate 1 Replicate 2 Units 

Dilute Solution 1 μmol/L of Dilute Solution

Dilute Solution 2 μmol/L of Dilute Solution

Dilute Solution 3 μmol/L of Dilute Solution

5% MPA Diluent μmol/L of Diluent 

CS #2 μmol/L of Sample 

Target: 28.05 μmol/L 

(27.56 μmol/L to 28.54 μmol/L;

95 % confidence interval)

Serum Test Sample #361 μmol/L of Sample 

Serum Test Sample #362 μmol/L of Sample 

Serum Test Sample #363 μmol/L of Sample 

Serum Test Sample #364 μmol/L of Sample 

Were samples frozen upon receipt? Yes | No 

Analysis method: HPLC-EC | HPLC-Fluor DAB | HPLC-OPD | HPLC-UV | AO-OPD | Other 

If “Other”, please describe: 

COMMENTS: 

E6
Participant #: ________ Date: _____________

This box contains one vial each of the following six VitC M2QAP samples:

Label Form

VitC #361 Liquid frozen (1:1 serum:10% MPA) SRM970 Lv1

VitC #362 Liquid frozen (1:1 serum:10% MPA) New1 (5)

VitC #363 Liquid frozen (1:1 serum:10% MPA) New4 (31)

VitC #364 Liquid frozen (1:1 serum:10% MPA) New5 (46)

CS #2 Liquid frozen (1:1 serum:10% MPA) SRM970 Lv2

Control Solid AA

Please 1) Open the pack immediately

2) Check that it contains one vial each of the above samples

3) Check if the samples arrived frozen

4) Store the samples at -20  ̊C or below until analysis

5) Complete the following information

6) Fax the completed form to us at 301-977-0685

(or email requested information to david.duewer@nist.gov)

1) Date this shipment arrived: ___________________________

2) Are all of the vials intact? Yes | No

If "No", which one(s) were damaged?

3) Was there any dry-ice left in cooler? Yes | No

4) Did the samples arrive frozen? Yes | No

5) At what temperature are you storing the samples? _______  ̊C

6) When do you anticipate analyzing these samples? ________________________

Your prompt return of this information is appreciated.

The M2

QAP Gang

Packing List and Shipment Receipt Confirmation Form

NIST Micronutrients Measurement Quality Assurance Program

Vitamin C Round Robin 36

Mail: M2QAP

 NIST, Stop 6392

 Gaithersburg, MD 20899-6392

Fax: 301-977-0685

Email: David.Duewer@NIST.gov

E7
Appendix F. Final Report for RR36 

The following five pages are the final report as provided to all participants: 

 Cover letter. 

 An information sheet that: 

o describes the contents of the “All-Lab” report, 

o describes the content of the “Individualized” report, 

o describes the nature of the test samples and details their previous distributions, if any, and 

o summarizes aspects of the study that we believe may be of interest to the participants. 

F1
May 10,2012 

Dear Colleague: 

UNITED STATES DEPARTMENT OF COMMERCE 

National Institute of Standards and Technology 

Gaithersburg, Maryland 20899-

Enclosed is the summary report of the results for Round Robin 36 (RR36) for the measurement of total 

ascorbic acid (T AA, ascorbic acid plus dehydroascorbic acid) in human serum. Included in this report 

are a summary of data for all laboratories and an individualized summary of your laboratory's 

measurement performance. The robust median is used to estimate the consensus value for all samples, 

the "adjusted median absolute deviation from the median" (MADe) is used to estimate the expected 

standard deviation, and we estimate the coefficient of variation (CV) as 100xMADe/median. 

RR36 consisted of four test samples (S36:1, S36:2, S36:3, and S36:4), one serum control material 

(CS#2), and one solid control material for preparation ofTAA control solutions. Details regarding the 

samples can be found in the enclosed report. 

If you have concerns regarding your laboratory's performance, we suggest that you obtain and analyze a 

unit of Standard Reference Material (SRM) 970 Vitamin C in Frozen Human Serum. SRM 970 can be 

purchased from the NIST SRM Program at www.nist.gov/srm; phone: 301-975-6776; fax: 301-948-3730. 

If your measured values do not agree with the certified values, we suggest that you contact us for 

consultation. 

Samples for the second vitamin C round robin (RR37) of the 2012 MMQAP will be shipped starting 

June 25,2012. Please contact us immediately if this schedule is problematic for your laboratory. 

If you have questions or concerns regarding this report, please contact David Duewer at 301-975-3935; email: david.duewer@nist.gov or me at 301-975-3120; e-mail: jbthomas@nist.gov; or fax: 301-977-0685. 

ea ice Brown Tho 

Re arch Chemist 

alytical Chemistry Division 

Material Measurement Laboratory 

Enclosures 

cc: L. C. Sander 

David L. Duewer, Ph.D. 

Research Chemometrician 

Analytical Chemistry Division 

Material Measurement Laboratory 

F2
The NIST MMQAP Vitamin C Round Robin 36 (RR36) report consists of: 

Page “Individualized” Report 

1 Summary of your reported values for the nominal 55 mmol/L solution you prepared from the 

ascorbic acid solid control sample, the serum control sample, and the four serum test 

samples. 

2 Graphical summary of your RR36 sample measurements. 

Page “All-Lab” Report 

1 A tabulation of results and summary statistics for total ascorbic acid [TAA] in the RR36 

samples and control/calibration solutions. 

Serum-Based Samples. One serum control and four test samples were distributed in RR36. 

CS#2 SRM 970 level 2, ampouled in mid-1998 

S36:1 Ampouled in late 2009, previously distributed as sample S34:4 (RR34, Spring 2010). This is 

the same material as S36:4. 

S36:2 Ampouled in late 2009, previously distributed as sample S32:3 (RR32, Fall 2009) and S35:3 

(RR35, Fall 2010) 

S36:3 SRM 970 level 2, ampouled in mid-1998, previously distributed as an “Unknown” in RRs 11 

to 15, 18, 20 22, 25, and 29 

S36:4 Ampouled in late 2009, previously distributed as sample S34:4 (RR34, Spring 2010). This is 

the same material as S36:1. 

Results. 

1) All participants who prepared the four 5% metaphosphoric acid (MPA) control/calibration solutions 

(the three “Dilute Solutions” and the “Diluent”) did so correctly. The criteria used to evaluate this 

success are: the density of the 5% MPA solution (≈1.03 g/mL), the observed wavelength maximum 

of “Dilute Solution #1” (≈244 nm), the observed absorbance at that maximum (≈0.58), and the 

calculated E1%#1” (≈560 dL/g·cm). 

2) The Measured = a+b*Gravimetric calibration parameters for the control/calibration solutions 

(columns 10 to 13 of the All-Lab Report) indicate that the measurement systems for all participants 

are linear (R2

 close to 1 and the root-mean-square (RMS) residual close to 0.0) and well calibrated 

(intercepts close to 0 and slopes close to 1). 

3) The Measured = p+q*Median regression parameters for samples S36:1 to S36:4 (columns 23 to 26 of 

the All-Lab Report) confirm the linearity of all measurement systems (R2

 close to 1 and RMS close to 

0.0). However, the intercepts and slopes indicate that there are systematic differences in the response 

of the various measurement procedures to the TAA in the 5% aqueous metaphosphoric acid (MPA) of 

the test samples. 

The consequences of these differences are directly visualized by comparing results for Samples S36:1 

and S36:4. Figure 1 is a Youden Plot, displaying the reported values for S36:1 against those for 

S36:4. These two samples are the same material – the only difference being that the S36:1 vials 

represent the beginning of the production run and the S36:4 vials represent the end of the run. 

Each solid blue dot in Figure 1 represents the average of the two replicate results for S36:1 and for 

S36:4 reported by one participant, with the thin blue “error bars” spanning the replicate range. The 

longer these lines, the less stable the participant's measurement process and/or the materials over the 

time course of the measurements. The difference between replicates is not a significant source of 

variation for the large majority of participants. 

F3
49

51

53

55

57

59

61

63

65

49 51 53 55 57 59 61 63 65

[Total AA] in S36:1, μmol/L

[Total AA] in S36:4, μmol/L

Median

Reported

95 % CI

Y = X

Figure 1: Youden Plot of the Reported Results for S36:1 and S36:4 

The black 45° line represents equality between measurements of the two samples. The red circle is an 

approximate 95 % confidence interval on the joint distribution of the within-sample averages, 

estimated using robust methods and assuming that all measurements are independent. The center of 

the circle is the median of all of the available TAA results for this material. The radius is defined 

from the adjusted median absolute differences from the median (MADe) of the same complete data 

set. The solid red diamond at the center of the 95 % CI circle marks the median of the average results 

for S36:1 and for S36:4. The medians are nearly equal, indicating that there is very little difference in 

TAA content between the vials taken from the beginning of the production run and those from the 

end. 

If there was significant between-vial variation in the amount of TAA across the production run and/or 

if the participants’ measurement processes were not stable over the course of the serum test sample 

measurements, then the blue dots would be expected to be distributed in a rather wide band around 

the equality line. Since nearly all of the blue dots lie quite close to the equality line, we conclude that 

1) the material is adequately homogenous and 2) all of the participants’ measurement processes are 

relatively stable. 

If all of the participants’ measurement processes provided closely concordant results for the 

S36:1/S36:4 material, then no more than one of the blue dots would be expected to be located outside 

of the red circle. Three of the ten dots are along the line but well outside the circle, two quite high 

and one quite low. The measurement processes that produced these results are thus internally 

consistent but are significantly biased relative to those used by the other participants. 

One reason for asking participants to prepare control/calibration solutions from the solid control 

material is to test whether use of a common calibration material would make results from the different 

measurement procedures more concordant. The information provided on the preparation and 

measurement of the control/calibration solutions provide that common reference –assuming that there 

are no significant differences in measurement system response to TAA in 5 % aqueous MPA and 

TAA in 1:1 mixtures of plasma and 10 % aqueous MPA. 

F4
Figure 2 displays the results of re-calibrating the reported results to each participant's individually 

prepared control solutions. This calibration was accomplished by projecting the as-reported results 

onto the least-squares fit of the control solution results as a linear function of their preparative values. 

The values for these intercept, a, and slope, b, parameters are listed in the All-Lab Report. The 

calibrated results are defined as: Calibrated = (Measured - a)/b. The open blue dots represent the 

control-solution calibrated results, with the blue lines connecting calibrated and the reported values. 

49

51

53

55

57

59

61

63

65

49 51 53 55 57 59 61 63 65

[Total AA] in S36:1 μmol/L

[Total AA] in S36:4, μmol/L

Reported

Calibrated to Contols

95 % CI

Y = X

A

Figure 2: Youden Plot of Control-Solution Calibrated Results for S36:1 and S36:4. 

While calibration to the control solutions does reduce the differences among the results nearest the 

center of the circle, it does little to reduce the larger differences between this central group and all of 

the others. Thus the differences in results among the measurement procedures cannot be explained 

just by differences in measurement system response to TAA in 5 % aqueous MPA. 

If the among-procedure differences arise from differences in response to 1:1 mixtures of plasma and 

10 % aqueous MPA, then linear calibration to the two components of SRM 970 would be expected to 

improve concordance. Only one of the two components (Level 2, aka CS#2) was distributed in RR36 

so this hypothesis cannot be directly tested using the S36:1 and S36:4 data. However, it can be 

indirectly tested using results from RR20 to RR25 where SRM 970 Level 1 (aka CS#1) and Level 2 

were both distributed. 

Figure 3 displays summary statistics for the 20 test samples distributed in these 6 RRs as a function of 

the mean values, with the bottom panel displaying SD as a function of analyte mean and the top panel 

displaying the same data as % CV (100·SD/Mean). The solid green diamonds represent the summary 

statistics estimated from the as-reported results, and the open pink diamonds represent the summaries 

after projecting the reported results onto the line connecting the results for the CS#1 and CS#2 serum 

controls. The green lines represent a best-fit model for the SD of the as-reported data; the pink lines 

represent a model for the serum control-transformed data. Between-participant variability is about 

halved by calibrating to SRM 970. 

F5
0

5

10

15

20

25

30

%CV [TAA], 100·SD/Mean

0

2

4

6

8

0 10 20 30 40 50 6

Mean [TAA], μmol/L

SD [TAA], μmol/L

0

As reported

Calibrated to serum controls

  2 2 0.131.6SD  Mean)

  2 2 0SD 95. 0.063  Mean)

Figure 2: Precision Functions for the Results from RR20 to RR25. 

Top) % CV as a function of Mean; Bottom) SD as a function of Mean 

The reduction in between-participant variability following calibration to the reported results for the 

SRM 970 materials used as serum control solutions strongly suggests that some measurement 

procedures react rather differently to TAA in 5 % aqueous MPA than to 1:1 solutions of plasma and 

10 % MPA. While such a difference does not necessarily indicate anything about the performance of 

a given measurement procedure for other sample matrices, it does suggest that there may be 

unexplained influences at work. 

If you are concerned about the accuracy of your measurement procedure for TAA in the 1:1 plasma 

and 10 % MPA matrix, we recommend the following diagnostic procedure: 1) calibrate your 

measurement procedure in your routine manner, 2) measure both levels of SRM 970 enough times so 

that the standard deviation of the mean, SD/√n, of the measurements is less than about 0.5 mmol/L, 3) 

compare your measurements with the certified 95 % level of confidence intervals: (7.75 to 9.07) 

mmol/L and (27.56 to 28.54) mmol/L. If your mean values are not both within the appropriate 

certified range, then it is unlikely that your measurement process provides accurate results for TAA in 

1:1 mixtures of plasma and 10 % aqueous MPA. 

F6
Appendix G. “All-Lab Report” for RR36 

The following single page is the “All-Lab Report” as provided to all participants, with two 

exceptions: 

 the participant identifiers (Lab) have been altered. 

 the order in which the participant results are listed has been altered. 

The data summary in the “All-Lab Report” has been altered to ensure confidentiality of 

identification codes assigned to laboratories. 

G1
Micronutrients Measurement Quality Assurance Program for Total Ascorbic Acid

"Round Robin" 36

MPA

Density

Lab Date Dil:1 Dil:2 Dil:3 Dil:1 Dil:2 Dil:3 MPA Inter Slope R2 RMS g/mL max Amax E1% CS#2 S36:1 S36:2 S36:3 S36:4 Inter Slope R2 RMS CS#2 S36:1 S36:2 S36:3 S36:4

VC-MA 02/02/12 57.9 28.7 14.8 60.6 29.2 14.9 0.0 -0.43 1.05 1.000 0.5 1.034 244. 0.5610 550.5 28.4 59.6 32.8 28.4 60.0 0.17 1.03 1.000 0.4 27.5 57.1 31.6 27.5 57.5

VC-MB 07/03/12 57.9 28.7 14.3 59.1 29.4 13.4 0.0 -0.42 1.03 0.999 0.7 1.029 243.5 0.5700 558.6 27.6 57.3 31.0 26.3 56.0 -0.62 0.99 0.998 0.9 27.3 56.2 30.6 26.0 54.9

VC-MC 12/04/12 59.1 29.5 14.8 59.4 29.9 14.9 0.0 0.08 1.00 1.000 0.1 1.028 243. 0.5854 562.0 28.3 65.7 35.7 30.6 66.0 -0.94 1.16 1.000 0.5 28.1 65.3 35.5 30.4 65.6

VC-MG 10/04/12 63.8 32.9 17.0 66.1 32.7 16.7 0.0 -0.65 1.04 0.999 0.9 1.028 243.6 0.6480 576.5 28.2 59.1 31.6 28.4 58.7 -0.11 1.02 1.000 0.3 27.8 57.5 31.0 28.0 57.2

VC-MH 17/04/12 56.1 27.9 13.9 57.7 28.6 14.5 0.0 0.02 1.03 1.000 0.1 1.029 243.6 0.5602 567.1 28.3 58.2 32.1 28.0 58.3 0.57 1.00 1.000 0.3 27.5 56.5 31.2 27.2 56.6

VC-MI 10/04/12 56.8 28.3 14.1 56.7 28.6 14.4 0.0 0.18 1.00 1.000 0.2 1.031 27.5 57.2 30.2 27.5 57.5 -0.83 1.01 0.999 0.5 27.4 57.2 30.1 27.4 57.6

VC-MJ 01/04/12 55.2 26.5 14.9 56.4 28.3 14.7 0.7 0.48 1.02 0.999 0.9 1.024 255a 0.340

a 349.9

a 30.9 66.3 39.3 31.4 65.8 2.96 1.09 0.991 2.0 29.9 64.8 38.2 30.4 64.3

VC-MN 02/04/12 58.4 28.8 14.2 63.3 31.1 14.7 0.0 -0.31 1.09 1.000 0.4 1.030 243.9 0.5886 572.5 27.8 51.1 29.2 24.3 50.0 1.69 0.85 0.996 1.1 25.8 47.3 27.1 22.6 46.3

VC-NF 05/04/12 55.9 28.2 14.0 56.5 28.7 14.2 0.0 0.06 1.01 1.000 0.1 1.033 244. 0.5410 549.3 28.4 53.6 28.8 27.5 54.5 1.28 0.91 0.997 1.0 28.1 53.0 28.5 27.1 53.9

VC-NM 07/03/12 54.9 27.6 14.1 56.4 30.5 14.3 0.0 0.34 1.03 0.998 1.3 1.032 242. 0.5440 562.2 25.4 56.1 30.1 27.2 53.6 1.47 0.92 0.995 1.3 24.2 53.9 28.9 26.0 51.6

10 10 10 10 10 10 10 10 8 8 8 10 10 10 10 10 10 10 10 10 10

57.6 28.7 14.6 59.2 29.7 14.7 0.1 1.030 243.4 0.5748 562.4 28.1 58.4 32.1 27.9 58.0 27.4 56.9 31.3 27.3 56.6

2.6 1.7 0.9 3.3 1.4 0.8 0.2 0.003 0.7 0.0342 9.6 1.4 4.7 3.2 2.0 5.0 1.5 5.3 3.3 2.2 5.6

54.9 26.53 13.9 56.4 28.32 13.4 0.0 1.024 242.0 0.5410 549.3 25.4 51.1 28.8 24.3 50.0 24.2 47.3 27.1 22.6 46.3

56.0 27.95 14.1 56.5 28.59 14.3 0.0 1.028 243.4 0.5562 556.6 27.7 56.3 30.1 27.3 54.9 27.3 54.5 29.2 26.3 54.257.3 28.50 14.2 58.4 29.32 14.6 0.0 1.029 243.6 0.5655 562.1 28.2 57.7 31.3 27.7 57.9 27.5 56.8 30.8 27.3 56.958.3 28.81 14.8 60.3 30.35 14.8 0.0 1.032 243.9 0.5862 568.5 28.4 59.4 32.6 28.4 59.7 28.0 57.4 31.5 27.8 57.563.8 32.91 17.0 66.1 32.68 16.7 0.7 1.034 244.0 0.6480 576.5 30.9 66.3 39.3 31.4 66.0 29.9 65.3 38.2 30.4 65.6

2.0 0.7 0.3 2.9 1.1 0.4 0.0 0.0 0.5 0.0307 11.4 0.5 2.6 2.0 1.0 4.0 0.6 2.6 2.1 1.4 3.7

3 32 5 43 0.24 0.20 5.4 2.0 2 4 6 4 7 25757

a)

%75

Grav, mol/L

Min

CV

%25

Median

%75

Max

SD

Dilute Solution 1 Control / Calibration Samples

Measured = a + b*Grav Measured, mol/L Spectrophotometry

SD

Calibrated, μmol/L Measured = p+q*Median Measured, μmol/L

N

SD

N

Samples

5% Trichloroacetic acid solution

Average

Max

eSD

Min

CV

%25

Median

Average

[Report]RR36_ALR-VC_Coded.xls

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Appendix H. Representative “Individualized Report” for RR36 

Each participant in RR36 received an “Individualized Report” reflecting their reported results. The 

following two pages are the “Individualized Report” for participant “VC-MA”. 

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MPA

Density

Date RR Method g/mL max Amax E1% Inter Slope R2 SEE

09/10/09 31 HPLC-EC 1.036 244.0 0.566 546.1 -0.1 1.02 1.000 0.20

02/24/10 32 HPLC-EC 1.035 242.0 0.566 545.1 0.3 1.03 1.000 0.46

09/27/10 33 HPLC-EC 1.037 244.0 0.560 540.5 0.4 1.08 1.000 0.43

02/28/11 34 HPLC-EC 1.039 244.0 0.575 555.2 0.6 1.14 1.000 0.78

08/24/11 35 HPLC-EC 1.039 242.0 0.568 547.7 0.0 1.03 1.000 0.24

02/02/12 36 HPLC-EC 1.035 244.0 0.561 550.5 -0.4 1.05 1.000 0.55

Mean 1.037 243.3 0.57 547.5 0.48

SD 0.002 1.0 0.01 5.0

CV 0.20 0.42 1.0 0.9

Date RR Sample Rep1 Rep2 Fadj Mean SDdup N Mean SDrepeat SDreprod

02/23/04 20 CS#2 25.8 26.2 1.0 26.0 0.3 12 28.4 0.4 1.6

09/13/04 21 CS#2 26.2 27.2 1.0 26.7 0.7

03/08/05 22 CS#2 29.0 29.0 1.0 29.0 0.0

10/17/05 23 CS#2 29.4 30.5 1.0 30.0 0.8

03/09/06 24 CS#2 29.2 29.1 1.0 29.2 0.1

08/28/06 25 CS#2 27.2 28.1 1.0 27.6 0.6

10/05/07 27 CS#2 28.1 27.4 1.0 27.7 0.5

08/11/08 29 CS#2 27.2 27.2 1.0 27.2 0.0

09/10/09 31 CS#2 31.8 32.2 1.0 32.0 0.3

02/24/10 32 CS#2 28.6 29.0 1.0 28.8 0.3

02/28/11 34 CS#2 28.3 27.6 1.0 27.9 0.5

02/02/12 36 CS#2 28.5 28.3 1.0 28.4 0.1

09/23/98 11 S11:2:A 50.7 47.7 0.5 24.6 1.1 11 26.6 0.5 1.9

04/02/99 12 S12:2:A 49.5 45.9 0.5 23.9 1.3

09/17/01 13 S13:2 27.6 27.7 1.0 27.7 0.1

09/27/01 14 S14:4 25.7 26.4 1.0 26.0 0.5

09/18/01 15 S15:2 25.4 25.6 1.0 25.5 0.2

03/20/03 18 S18:3 28.8 29.2 1.0 29.0 0.3

02/23/04 20 S20:4 25.9 25.2 1.0 25.5 0.5

03/08/05 22 S22:4 29.4 29.4 1.0 29.4 0.0

08/28/06 25 S25:2 27.6 27.4 1.0 27.5 0.1

08/11/08 29 S29:3 25.6 25.7 1.0 25.6 0.1

02/02/12 36 S36:3 28.3 28.5 1.0 28.4 0.1

02/24/10 32 S32:3 33.4 32.8 1.0 33.1 0.5 3 33.1 0.3 0.3

08/24/11 35 S35:3 33.4 33.4 1.0 33.4 0.1

02/02/12 36 S36:2 32.8 32.8 1.0 32.8 0.0

02/28/11 34 S34:4 58.1 58.4 1.0 58.3 0.2 3 59.3 0.2 0.9

02/02/12 36 S36:1 59.5 59.7 1.0 59.6 0.1

02/02/12 36 S36:4 59.7 60.2 1.0 60.0 0.3

Vitamin C "Round Robin" 36 Report: Participant VC-MA

[TAA] mmol/Lsample

Dilute Solution 1

Ymeas = Inter + Slope* Xgrav

Control/Calibration Solutions

Spectrophotometry

Pooled SEE

Email: david.duewer@nist.gov

Please check our records against your records. Send corrections and/or updates to...

Micronutrients Measurement Quality Assurance Program

National Institute of Standards and Technology

100 Bureau Drive Stop 6392

Gaithersburg, MD 20899-6392 USA

Fax: (301) 977-0685

5/8/2012 [ILR_RR36_Coded.XLS]Summary Page 1/2

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Vitamin C "Round Robin" 36 Report: Participant VC-MA

Total Ascorbic Acid, μmol/mL

For details of the construction and interpretation of these plots, see:

Duewer, Kline, Sharpless, Brown Thomas, Gary, Sowell. Anal Chem 1999;71(9):1870-8.

Sample

S36:1 VitC #361, previously distributed in RR 34. Same material as S36:4

S36:2 VitC #362, previously distributed in RRs 32, 35

S36:3 VitC #363, SRM 970 Lv II. Previously distributed in RRs 11 to 15, 18, 20, 22, 25, 29

S36:4 VitC #364, previously distributed in RR 34. Same material as S36:1

Comments

S11:2S12:2S13:2S14:4S15:2S18:3S20:4S22:4S25:2S29:3S36:3S32:3S35:3S36:2S34:4S36:1S36:4

[Total Ascorbic Acid], μmol/L

Apparent Precision, SD

Concordance, SD

Median [Total Ascorbic Acid], μmol/L

Your [Total Ascorbic Acid], μmol/L

 You, this RR

 You, past RRs

 NIST, RR 22

 Others, this RR

3rd Quartile (75%)

Median (50%)

1st Quartile (25%)

5/8/2012 [ILR_RR36_Coded.XLS]Pics Page 1/2

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