CCQM-K12.1: Subsequent Key Comparison on the...

1

CCQM-K12.1: Subsequent Key Comparison on the Determination of

Creatinine in Serum

Final Report

September 2006

Lian Hua Shi, Byung-Joo Kim, Hwa-Shim Lee, and Sang-Ryoul Park

Korea Research Institute of Standards and Science (KRISS)

Daejeon, Korea

Miryan Balderas Escamilla and Melina Pérez Urquiza

Centro Nacional de Metrología (CENAM)

Querétaro, México

Hisashi Kato

National Metrology Institute of Japan (NMIJ)

Tsukuba, Japan

Can Quan and Hongmei Li

National Research Center for Certified Reference Materials (NRCCRM)

Beijing, China

INTRODUCTION

The accuracy and traceability of routine clinical diagnostic tests has become a matter of

great concern. Inconsistency in test results due to the lack of high quality measurement

standards implemented in clinical practices often leads to confusion in making medical

decisions as well as unnecessary and costly repeats of tests. This problem has been

legally addressed by the European Union to implement of an In-vitro Diagnostic (IVD)

Directive. Other parts of the world are likely to follow the EU in requiring greater

traceability for IVD products. Upon this change, CIPM, IFCC, and several other related

international organizations have organized the Joint Committee on Traceability in

Laboratory Medicine (JCTM) to help implementation of measurement standards in the

field of laboratory medicine [1]. National metrology institutes (NMIs) are to take great

2

responsibility in development and dissemination of measurement standards of higher

order. Therefore, Key Comparisons of substances of great diagnostic values have been

actively organized and carried out under CCQM.

Creatinine is an important diagnostic marker for renal function, and is frequently

measured in various clinical situations. Routine clinical tests mostly based on enzymatic

reactions, however, are often subject to interferences from various materials coexisting

with creatinine in samples. Therefore, the accuracy of clinical tests is still of great

concern. CCQM Organic Analysis Working Group (OAWG) had performed a key

comparison of determination of creatinine in human serum (CCQM-K12) in which five

NMIs had participated. The results are available from the BIPM KCDB [2].

There were other NMIs that needed to demonstrate their measurement capability

through a form of KC. Reflecting upon the current situation, the chair of OAWG

arranged for a subsequent Key Comparison (CCQM-K12.1). Under the guidance of

OAWG, KRISS who demonstrated its measurement capability in CCQM-K11

coordinated the Subsequent Key Comparison.

CENAM (Mexico), NMIJ (Japan), and NRCCRM (China) participated in the

Subsequent Key Comparison, and two sets of test materials representing normal and

elevated creatinine levels in human serum were sent. Results were received from

CENAM and NRCCRM. NMIJ withdrew from the Key Comparison because of some

technical difficulties in measurement. Returned data were presented in OAWG fall

meeting of 2005 with minimum data processing, and no significant comments on the

results of the Subsequent Key Comparison were made by OAWG. In the draft

document of the final report, modifications of initially reported expanded uncertainties

were made as NRCCRM and KRISS found needs for correction in their assessments. As

not allowed, no modification was made in the initially reported mean values. The draft

document of the final report was submitted and discussed during the CCQM OAWG

meeting in April 2006.

The draft of the final report was submitted to the 2006 April meeting of OAWG,

OAWG decided to place the originally reported expanded uncertainties by participants

as the final values. This recommendation has been reflected in the revised report.

Corrections of some miscalculations in the previous draft repro were also made.

3

SUMMARY OF ORIGINAL CCQM-K12 STUDY

A Key Comparison on the determination of creatinine in human serum, CCQM-K12

was conducted in 2002 with National Institute of Standards and Technology (NIST) as

the coordinating laboratory. Five laboratories participated in this Key Comparison:

Country Institution

EU Institute of Reference Materials and Measurements, IRMM

Germany Physikalisch-Technische Bundesanstalt, PTB

Korea Korea Research Institute of Standards and Science, KRISS

The Netherlands NMi Van Swinden Laboratorium, NMi

UK Laboratory of the Government Chemist, LGC

USA National Institute of Standards and Technology, NIST (Pilot Lab)

The details of the study outcome can be found at the BIPM website [2]. The conclusion

of the study was that the participating NMIs could successfully measure serum

creatinine at normal and elevated levels, using ID/MS-based methods, with

interlaboratory expanded uncertainties of less than 0.8%. The essential part of the

results of CCQM-K11 is presented in Table 1.

CONDUCT OF THIS STUDY (CCQM-K12.1; CCQM-K12-Subsequent)

Participants

The following five countries participated in this study:

Country Institution

China National Research Centre for Certified Reference Materials, NRCCRM

Japan National Metrology Institute of Japan, NMIJ (data not returned)

Korea KRISS (Coordinating Laboratory)

Mexico National Center of Metrology, CENAM

NMIJ had received test materials, but experienced a technical difficulty in measurement,

and decide not to return data. KRISS is the only laboratory participated in CCQM-K12

and had demonstrated capability for accurate measurement of creatinie in human serum.

Therefore, KRISS, the coordinating laboratory was to provide a link to CCQM-K12 for

the results of this study.

4

Methods Used for the CCQM-K12-Subsequent Comparison

NIMJ measured creatinine in serum by ID-LC-MS method. The reproducibility of

measurements was very poor to report the results. NMIJ scientists detected unknown

peaks at m/z 114, and peak areas increased by the time spent on the defrosted the serum

sample in the refrigerator. For this problem, NMIJ decided to withdraw from this

Subsequent Key Comparison. No other laboratories reported a similar problem.

All participants including NMIJ used LC/ID-MS. KRISS used ultra-filtration with 3000

Da cut-off filters for removal of proteins. Other laboratories precipitated proteins with

acetonitrile or ethanol. KRISS used NIST SRM 914a as the high purity creatinie for

preparation of standard solutions. CENAM and NRCCRM used commercial chemical

products from Aldrich and Fluka, respectively. CENAM determined the purity of the

high purity creatinine by itself. NRCCRM took of 1 % of estimated uncertainty in purity

determination. CENAM and KRISS validated their measurement procedures with the

reference materials of CRM DMR-963a and NIST SRM 909b, respectively. Table below is

the summary of the methods used by each laboratory.

Laboratory Sample prep. &

Derivatization

Measurement Calibration

material

Validation

CENAM Acetonitrile precip.,

no derive.

LC/ID-MS Aldrich* CRM DMR-

963a

KRISS Ultra-filtration

(3000 Da), no derive.

LC/ID-MS NIST SRM 914a NIST SRM 909b

NMIJ NA (suffered from

poor reproducibility

NA

(LC/ID-MS)

NA NA

NRCCRM Ethanol precip.,

no derive.

LC/ID-MS Fluka, > 99%

* Purity was determined by CENAM.

Materials Used for the CCQM-K12-Subsequent Comparison

Candidate certified reference materials of human serum prepared by KRISS were used

as test materials in this study. The test materials were natural human serum to which no

preservative was added. Only antiseptic filtering and/or fortification were applied.

5

Homogeneities of creatinine were estimated 0.65 % and 0.75% RSD for Test Material

01B and Test Material 02B, respectively as presented in the figures below. Target

ranges were given as follows:

01B 02B

Creatinine 4 - 7 mg/kg 20 – 40 mg/kg

0 2 4 6 8 10

0.90

0.95

1.00

1.05

1.10

RSD = 0.65 %

De

via

tio

n

Vial Number

0 2 4 6 8 10

0.90

0.95

1.00

1.05

1.10

RSD = 0.75 %

De

via

tio

n

Vial Number

0 2 4 6 8 10

0.90

0.95

1.00

1.05

1.10

RSD = 0.65 %

De

via

tio

n

Vial Number

0 2 4 6 8 10

0.90

0.95

1.00

1.05

1.10

RSD = 0.75 %

De

via

tio

n

Vial Number

Results of homogeneity test of the test materials for creatinine measurement.

The test materials were to be kept frozen (either at -20 oC or at -70

oC ). However, no

visible sign of degradation was observed during storage at room temperature for several

weeks as far as the seals were intact. Each test material consisted of 4 vials of 3 mL of

human serum. For the set of 4 vials, one is for practice and/or for better determining the

target concentration whereas the rest 3 vials are for measurement. The test materials

were sent as packed with a sufficient amount of dry ice to keep them frozen for several

days. However, test materials sent to NRCCRM were exposed to ambient temperature

for about two weeks because of trouble at custom offices. Stability of creatinine in this

storage condition was not performed. Because of the absence of any assuring delivery

mean, NRCCRM performed the measurements without replacement of originally

received test materials.

6

Measurement Protocol and Calculation of Uncertainty

As requested, all participants except NMIJ produced two independent results from each

vial of a test material. Three vials of a test material were distributed. Therefore, 6

measurements were resulted from each test material. The results were to be reported on

an absolute basis (corrected for chemical purity of the calibration material used by the

participant) together with the expanded uncertainty. Space was provided at the end of

the data reporting sheets for inclusion of a full uncertainty budget, including definition

of terms and assessment of which components made significant contributions.

Linking the Subsequent Key Comparison to the Original Key Comparison

The results of CCQM-K12-Subsequent were initially treated as if an independent Key

Comparison was carried out (Table 2-1 & 2-2). Then, liking them to the results of the

original Key Comparison was made by applying proportionality factors obtained

through comparison of KRISS results from both Key Comparisons. KRISS results from

the Subsequent Key Comparison were assumed to have the same fractions of deviation

from KCRVs (virtual values) as determined in the original Key Comparison. From this

assumption, KCRVs of the Subsequent Comparison were assigned as noted as assigned

KCRVs in Table 3. Although concentrations of creatinine were not exactly matched, the

results of Test Material 01B of CCQM-K12.1 were related to the results of Material I of

CCQM-K12 as a normal creatinine level whereas Test Material 02B of CCQM-K12.1

was related to Material II of CCQM-12 as an elevated creatinine level.

Calculation of the assigned KCRVs is shown below.

Assignment of the KCRV for Test Material 01B of CCQM-K12.1:

Assigned KCRV = 5.939 mg/kg x (8.217/8.186) = 5.961 mg/kg

8.217 mg/kg: KCRV for Material I of CCQM-K12;

8.186 mg/kg: KRISS result for Material I of CCQM-K12;

5.939 mg/kg: KRISS result for Test Material 01B of CCQM-K12.1

Assignment of the KCRV for Test Material 02B of K12.1:

Assigned KCRV = 27.361 mg/kg x (18.645/18.539) = 27.517 mg/kg

18.645 mg/kg: KCRV for Material II of CCQM-K12;

18.539 mg/kg: KRISS result for Material II of CCQM-K12;

27.361 mg/kg: KRISS result for Test Material 02B of CCQM-K12.1

7

Expanded uncertainties were also linked to the results of original Key Comparison in

the same manner as applied for calculation of deviations of from KCRVs. Calculation

of adjusted uncertainties are shown below.

Adjustment of expanded uncertainties for Test Material 01B

Adjusted Uncertainties = Reported uncertainties x (1.9/0.92)

1.9 %: KRISS Rel. Uncertainty (%) for Material I of CCQM-K12;

0.92 %: KRISS Rel. Uncertainty (%) for Test Material 01B of CCQ-K12.1

Adjustment of expanded uncertainties for Test Material 02B

Adjusted Uncertainties = Reported uncertainties x (1.7/0.86)

1.7 %: KRISS Rel. Uncertainty (%) for Material II of CCQM-K12;

0.86 %: KRISS Rel. Uncertainty (%) for Test Material 02B of CCQ-K12.1

During the CCQM meeting in April 2006, Organic Analysis Working Group decided to

accept the originally reported expanded uncertainty by each participating laboratory as

the final values of the expanded uncertainty. Therefore, the values calculated above for

linking to the original study were not taken as the final values.

RESULTS

Results for the CCQM-K12-Subsequent Comparison are summarized in Table 2. The

uncertainty bars in the figures represent expanded uncertainties as reported by the

participating laboratories. Uncertainties in the results of NRCCRM were changed from

the values reported in OAWG fall meeting 2005 as requested by NRCCRM. KRISS

also refined its uncertainty budgeting procedure and made modifications of originally

reported uncertainties. Evaluation of uncertainty reported by each laboratory is

summarized in Table 5. The results of linking the results of this Subsequent Key

Comparison to the original Key Comparison are presented in Table 3. As decided by

OAWG, the uncertainties originally reported by participants were placed as the final

values regardless the results of linking to the results of CCQM K-11.

8

DISCUSSION

KRISS is the only laboratory participated in the original CCQM-K12 Key Comparison

[2]. KRISS, the coordinating laboratory, was to provide a link for this Subsequent Key

Comparison to the original Key Comparison. KRISS proved its capability for accurate

measurement of creatinine in human serum in the original Key Comparison study. In

addition, KRISS validated its measurement procedure by performing simultaneous

measurement of NIST SRM 909b as shown below.

NMIJ had experienced poor reproducibility problem and decided not to submit the

results. NMIJ scientists informed that they found an unknown peak of m/z 114, of

which area increased in a time course. If this phenomenon was responsible to the poor

reproducibility of measurement of creatinine, it may be related with cross conversion

between creatine and creatinine as described in the final report of CCQM-K11 [2].

NMIJ would have to solve this problem. No other participating laboratories reported a

similar problem.

50.389 ± 0.887KRISS measurement

50.317 ± 0.571Certified value

mg/kgLevel 2



mg/kgLevel 1

NIST SRM 909b

(freeze dry serum)



mg/kgLevel 2



mg/kgLevel 1

NIST SRM 909b

(freeze dry serum)

NRCCRM reported relatively smaller mean values for both test materials. Especially for

Test Material 01B, scattering of data was noticeable (See a figure below). One possible

reason for this scattering and underestimations would be degradation of creatinine due

to exposure of test materials to ambient temperature for about two weeks. Stability of

creatinine in serum media against a long term exposure to ambient temperature was not

tested yet. Inhomogeneity of the test materials is ruled out from the possible causes of

poor agreements of the reported results. Homogeneity of the test materials was proved

9

by the results of the homogeneity test shown above as well as high precision of reported

results of this study except NRCCRM’s results for Test Material 01B.

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

6.1

Cre

atinin

e (

mg

/kg

)

25.0

25.5

26.0

26.5

27.0

27.5

28.0

28.5

Cre

atin

ine (

mg

/kg

)

CE

NA

M

KR

ISS

NR

CC

RM

CE

NA

M

KR

ISS

NR

CC

RM

Test Material 01B Test Material 02B

Mean values reported by CENAM were relatively close to KRISS values. However,

deviations were slightly greater than the expanded uncertainties.

In overall, the results of the Subsequent Key Comparison were poorer than the outcome

of the original Key Comparison in both deviations and uncertainties. The lack of

performing a pilot study prior to participating in this Subsequent Key Comparison

might be the major reason for the poor outcome.

10

CONCLUSIONS

Probably because of lacking of participation in an adequate pilot study, the deviations

and uncertainties of CCQM-12-Subsequent Key Comparison were substantially larger

than the average results of the original Key Comparison. CENAM’s results were

relatively close to the KCRVs, and would be within the expanded uncertainties if the

values calculated for linking to the original study were taken. Nevertheless, CENAM

might need to improve the level of accuracy to the levels other NMIs demonstrated in

the original Key Comparison. NRCCRM might have encountered partially degraded test

materials as they reported substantially underestimating results. The test materials were

stored at ambient temperature for about two weeks at a customs office. If not done yet,

it will be helpful for NRCCRM to validate its measurement procedure using reliable

reference materials. NMIJ withdrew from the Subsequent Key Comparison due to a

technical difficulty. As proved in this study, having sufficient experience through a Pilot

Study prior to participating in a Key Comparison is valuable to demonstrate satisfactory

equivalence through a Key Comparison.

REFERENCES

[1] http://www.bipm.org/en/committees/jc/jctlm/

[2] http://kcdb.bipm.org/AppendixB/appbresults/ccqm-k12/ccqm-k12_final_report.pdf

http://kcdb.bipm.org/AppendixB/appbresults/ccqm-k12/ccqm-k12_final_report.pdf

11

Table 1-1. Results of CCQM-K12 Creatinine in Human Serum: Material I

units: mg/kg

Participant Mean Standard Un

certainty

Degrees of f

reedom

k Expanded

uncertainty

IRMM 8.360 0.1060 60 2.000 0.212

KRISS 8.186 0.0796 69 1.995 0.159

LGC 8.193 0.0080 60 2.000 0.016

NIST 8.277 0.0319 3.9 3.182 0.102

PTB 8.211 0.0289 60 2.000 0.058

Mean 8.217 excluding IRMM

Range (%) 2.12

Std dev of mean 0.0208

Degrees of Freedom 3

K factor 3.182

U 0.063

U(rel) % 0.81

KCRV 8.217 mg/kg 0.066 mg/kg

Table 1-2. Results of CCQM-K12 Creatinine in Human Serum: Material II

units: mg/kg

Participant Mean Standard Un

certainty

Degrees of f

reedom

k Expanded

uncertainty

IRMM 18.720 0.2396 60 2.000 0.479

KRISS 18.539 0.1627 503 1.965 0.320

LGC 18.614 0.0316 60 2.000 0.063

NIST 18.708 0.0722 3.9 3.182 0.230

PTB 18.718 0.0650 34.7 2.032 0.132

Mean 18.645 excluding IRMM

Range (%) 0.97



K factor: 3.182

U 0.14

U (rel) % 0.72


12

Table 2-1. Results of CCQM-K12.1 Creatinie in Human Serum: Test

Material 01B

Units: mg/kg

Participant Mean Comb. Std.

Uncertainty

Degrees of

freedom

k Expended

uncertainty

CENAM 5.745 0.031 1000 1.96 0.061

KRISS 5.939 0.027 31 2.04 0.055

NMIJ N/A N/A N/A N/A N/A

NRCCRM 5.58 0.12 60 2.00 0.24

Mean 5.754

Range (%) 6.3



K factor 4.30 (95% confidence level)

U 0.77

Relative U (%) 13


(treated as an independent study)

CE

NA

M

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

Cre

atin

ine

(mg/

kg)

KR

ISS

NR

CC

RM

CE

NA

M

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

Cre

atin

ine

(mg/

kg)

KR

ISS

NR

CC

RM

CE

NA

M

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

Cre

atin

ine

(mg/

kg)

KR

ISS

NR

CC

RM

13

Table 2-2. Results of CCQM-K12.1 Creatinine in Human Serum: Test

Material 02B

Units: mg/kg

Participant Mean Comb. Std.

Uncertainty

Degrees of

freedom

k Expanded

uncertainty

CENAM 28.26 0.13 1.96 0.25

KRISS 27.36 0.12 31 2.04 0.23

NMIJ N/A N/A N/A N/A N/A

NRCCRM 25.61 0.12 2.00 0.23

NMIJ data were excluded in the following calculations.

Mean 27.08

Range (%) 9.8



K factor 4.30 (95% confidence level)

U 5.8

Relative U (%) 21


(treated as an independent study)

26

27

28

Cre

atin

ine

(m

g/k

g)

CE

NA

M

KR

ISS

NR

CC

RM

26

27

28

Cre

atin

ine

(m

g/k

g)

CE

NA

M

KR

ISS

NR

CC

RM

14

Table 3-1. Link to the original study: Test Material 01B (normal creatinine

level)

Units: mg/kg; Linked KCRV = 5.961 (See Page 6, 7)

Participant Mean of

K12.1

Difference

from

KCRV

% Difference

from KCRV

% Rel.

uncertainty,K12.1

(Linked to K12)***

Finalized

rel.

uncertainty

(%)

CENAM 5.745 -0.22 -3.6 1.1 (2.24) 1.1

KRISS 5.939 -0.022 -0.37 0.92 (1.94) 0.92

NRCCRM 5.579 -0.38 -6.4 4.3 (9.03) 4.3

IRMM 1.7* 2.5

**

LGC -0.29* 0.20

**

NIST 0.73* 1.2

**

PTB -0.073* 0.71

**

* % difference in CCQM-K12;

** relative expanded uncertainty in CCQM-K12;

*** % relative uncertainty

calculated as linked to the results of CCQM-K12 assuming the uncertainty of KRISS was exactly

maintained.

-12

-10

-8

-6

-4

-2

0

2

4

6

% D

iffe

ren

ce f

rom

KC

RV

CE

NA

M

KR

ISS

NR

CC

RM

PT

B

NIS

T

LG

C

KR

ISS

IRM

M

CCQM-K12 CCQM-K12.1

-12

-10

-8

-6

-4

-2

0

2

4

6

% D

iffe

ren

ce f

rom

KC

RV

CE

NA

M

KR

ISS

NR

CC

RM

PT

B

NIS

T

LG

C

KR

ISS

IRM

M

CCQM-K12 CCQM-K12.1

15

Table 3-2. Link to the original study: Test Material 02B (elevated

creatinine level)

Units: mg/kg; Linked KCRV = 27.517 (See Page 6, 7)

Participant Mean of

K12.1

Difference

from

KCRV

% Difference

from KCRV

% Rel.

uncertainty,K12.1

(Linked to K12)***

Finalized

rel.

uncertainty

(%)

CENAM 28.26 0.74 2.7 0.91 (1.8) 0.91

KRISS 27.36 -0.16 -0.57 0.85 (1.7) 0.85

NRCCRM 25.6 -1.9 -6.9 0.85 (1.7) 0.85

IRMM 0.40* 2.6

**

LGC -0.17* 0.34

**

NIST 0.34* 1.2

**

PTB 0.39* 0.71

**

* % difference in CCQM-K12;

** relative expanded uncertainty in CCQM-K12;

*** % relative uncertainty

calculated as linked to the results of CCQM-K12 assuming the uncertainty of KRISS was exactly

maintained.

-10

-8

-6

-4

-2

0

2

4

6

% D

iffe

ren

ce f

rom

KC

RV

CE

NA

M

KR

ISS

NR

CC

RM

PT

B

NIS

T

LG

C

KR

ISS

IRM

M

CCQM-K12 CCQM-K12.1

-10

-8

-6

-4

-2

0

2

4

6

% D

iffe

ren

ce f

rom

KC

RV

CE

NA

M

KR

ISS

NR

CC

RM

PT

B

NIS

T

LG

C

KR

ISS

IRM

M

CCQM-K12 CCQM-K12.1

16

Table 4-1-A. Uncertainty Reports: Test Material 01B (CENAM)

Uncertainty Budget (Sources of uncertainty, their type, evaluation and magnitude) 01B

Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( ) (mg

g-1

)

Degrees

of

freedom

(i)

Type Source of

data

Method

precision

Between batch

precision for

the method as a

whole (major

source)

5.7454 0.0064 ˜ 1 5 A Replicate

analysis of

sample

across tree

samples

Calibration

solution

Concentration

of the

calibration

solution

(corrected for

purity) (major

source)

5.9462 0.0013 ˜ 1 5 A Gravimetric

preparation

Weight of

sample

Balance

linearity (minor

source)

0.6354 0.00004 large B Balance

calibration

certificate

Weight of

calibration

compound

Balance

linearity (minor

source)


calibration

certificate

ARsample Area Ratio

sample

1.0544 0.0026 ˜ 1 5 A Replicate

analysis of

sample

across tree

samples

ARstd Area Ratio

standard

1.0997 0.0058 ˜ 1 2 A Replicate

analysis

17

Table 4-1-B. Uncertainty Reports: Test Material 02B (CENAM)

Uncertainty Budget (Sources of uncertainty, their type, evaluation and magnitude) 02B

Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( ) (mg

g-1

)

Degrees

of

freedom

(i)

Type Source of

data

Method

precision

Between batch

precision for

the method as

a whole (major

source)

28.2563 0.0658 ˜ 1 5 A Replicate

analysis of

sample

across tree

samples

Calibration

solution

Concentration

of the

calibration

solution

(corrected for

purity) (major

source)

27.6171 0.0062 ˜ 1 5 A Gravimetric

preparation

Weight of

sample

Balance

linearity

(minor source)


calibration

certificate

Weight of

calibration

compound

Balance

linearity

(minor source)


calibration

certificate

ARsample Area Ratio

sample

1.0130 0.0084 ˜ 1 5 A Replicate

analysis of

sample

across tree

samples

ARstd Area Ratio

standard

0.9927 0.0027 ˜ 1 2 A Replicate

analysis of

sample

across tree

samples

18

Table 4-2-A. Uncertainty Reports: Test Material 01B (KRISS)

Uncertainty Budget (Sources of uncertainty, their type, evaluation and magnitude)

Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( )

Degrees of

freedom

(i)

Type Source of

data

Method

precision

Between batch

precision for the

method as a

whole (major

source)

5.9391

mg/kg

0.00745

mg/kg

~ 1 5 A Replicate

analysis of

sample

across tree

samples

Calibration

solution

Purity correction

(major source)

99.7% 0.3% ~ 1 large B Certified

value from

SRM

Provider

Weight of cal.

compound

2.2352

mg

0.002

mg

~ 1 large B Calibration

certificate

Weight of cal.

solution

26

g

0.00005

g


certificate

Standard

Solution

Accuracy in prep.

of std soln.

0.796871 0.00328 ~ 1 3 A Std dev of

R.F. of 4

std solns

u

(Mis_sol,std/Ms_sol,std)

1.0020073

0.0001421


certificate

Sample

solution

u

(Mis_sol,std/Ws)

0.2989 0.00010 ~ 1 large B Calibration

certificate

Random components were counted in method precision.

ARstd Repeatability

of determination

0.9870

0.00520

~ 1 4 A Replicate

analysis of

std. soln.

ARsample Counted in method precision

19

Table 4-2-B. Uncertainty Reports: Test Material 02B (KRISS)


Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( )

Degrees of

freedom

(i)

Type Source of

data

Method

precision

Between batch

precision for the

method as a

whole (major

source)

27.3615

mg/kg

0.036176

mg/kg

~ 1 5 A Replicate

analysis of

sample

across tree

samples

Calibration

solution

Purity correction

(major source)

99.7% 0.3% ~ 1 large B Certified

value from

SRM

Provider

Weight of cal.

compound

2.2352

mg

0.002

mg


certificate

Weight of cal.

solution

26

g

0.00005

g


certificate

Standard

Solution

Accuracy in prep.

of std soln.

0.796871 0.00328 ~ 1 3 A Std dev of

R.F. of 4

std solns

u

(Mis_sol,std/Ms_sol,std)

1.00201

0.00014


certificate

Sample

solution

u

(Mis_sol,std/Ws)

1.412078

0.000496


certificate

Random components were counted in method precision.

ARstd Repeatability

of determination

0.9870

0.00235

~ 1 4 A Replicate

analysis of

std. soln.

ARsample Counted in method precision

20

Table 4-3-A. Uncertainty Reports: Test Material 01B (NRCCRM)


Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( )

Degrees

of

freedom

(i)

Type Source of

data

Method

precision

Between

batch

precision for

the method as

a whole

(major

source)

5.579

mg/kg

0.0856

mg/kg

0.0856

mg/kg

5 A Replicate

analysis of

sample

across two

batches

Calibration

solution

Concentration

of the

calibration

solution

(corrected for

purity) (major

source)

5.514mg/kg 0.0032

mg/kg

0.059 mg/kg large B Supplier’s

specification

Weight of

sample

Balance

linearity

(minor

source)

0.48590g 0.000029 g -0.000599g large B Balance

calibration

certificate

Weight of

calibration

compound

Balance

linearity

(minor

source)

0.42290 mg 0.0058 mg 0.012 mg large B Balance

calibration

certificate

Other

Other

Other

Other

21

Table 4-3-B. Uncertainty Reports: Test Material 02B (NRCCRM)


Parameter Source of

uncertainty

xi u(xi)

f

xu x

i

i

( )

Degrees

of

freedom

(i)

Type Source of

data

Method

precision

Between

batch

precision for

the method as

a whole

(major

source)

25.613

mg/kg

0.115mg/kg 0.115mg/kg 5 A Replicate

analysis of

sample

across two

batches

Calibration

solution

Concentration

of the

calibration

solution

(corrected for

purity) (major

source)

25.705mg/kg 0.000205

mg/kg

0.0180mg/kg large B Supplier’s

specification

Weight of

sample

Balance

linearity

(minor

source)

0.49690g 0.000029g -0.001526

μg

large B Balance

calibration

certificate

Weight of

calibration

compound

Balance

linearity

(minor

source)

0.28110 mg 0.058 mg 0.005 mg large B Balance

calibration

certificate

Other

Other

Other

Other

Other

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