CENTRO DE METROLOGIA QUIMICA

1

CENTRO DE METROLOGIA QUIMICA

CALCULATION

OF

UNCERTAINTIES

FOR THE REPORT OF

ANALYSES

IN SIM.8.P1.2

(CHLORINATED PESTICIDES IN

HEXANE)

3

ANALYTICAL MEASUREMENT

• HEXACHLOROBENZENE

• gamma-HCH (g-BHC, LINDANE)

• HEPTACHLOR

• HEPTACHLOR EPOXIDE

• 2,4'-DDE

• CIS-CHLORDANE (ALPHA-CHLORDANE)

• TRANS-NONACHLOR

• DIELDRIN

• 4,4'-DDE

• 2,4'-DDD

• 2,4'-DDT

• 4,4'-DDT

• MIREX

Gas ChromatographPerkin-Elmer Model 8000 series 2 with Electron Capture Detector and manual injector

Column Phase, BP- 5 Col. Length, 50.00 mCol. i.d., 0.33 mm

Col. film thickness, 0.50 µm

4

ANALYTICAL MEASUREMENT

• NIST-SRM 2261 was used for the preparation of calibration standards.

• The quantification method used was bracketing using the method of internal standard.

• Sample of SIM.QM-P1 was selected as control

5

ANALYTICAL MEASUREMENT

GENERAL SCHEME OF ANALYTICAL MEASUREMENT

Gravimetric Preparation of standards, samples and

controls

Gravimetric Preparation of dilution

Verification of the standards through the calibration curve

Determination by bracketing using the method of internal standard

Statistical evaluation of the results and uncertainty calculation

6

GRAVIMETRIC PREPARATION OF STANDARDS

A m p o u le s S M R 2 2 6 1

s o l. IN T 1 s o l . IN T 3

S ta n d a rd B ra c k lo w

S ta n d a rd

B ra c k h ig h

IS – s o l. IN T

IS s o l id

7

BRACKETING SCHEME

120

58

40

20

8

4,4 ‘ -DDE

HCB, g-HCH, HEPTACLOR EPOXI, MIREX, 2’4-DDT, 4’4-DDT

DIELDRIN

HEPTACLOR (s/d), cis-CLORDANO, trans-

NONACLOR, 2’4-DDD, 2’4-DDE

ng/g

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THE UNCERTAINTY ESTIMATION PROCESS

SPECIFY MODEL ASSOCIATED TO THEMEASUREMENT

IDENTIFY UNCERTAINTY SOURCES

QUANTIFY UNCERTAINTY COMPONENTS

CONVERT TO STANDARD UNCERTAINTY

CALCULATE THE COMBINED UNCERTAINTY

OBTAIN EXPANDED UNCERTAINTY

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BRACKETING AND INTERNAL STANDARD

(AL/AIS)

(AH/AIS)

CL/CISCH/CIS

(AS/AIS)

CS/CIS

Sample concentration is calculated trough the equation:

SIClowstdC

SIAlowstdA

SIA

highstdA

SIAlowstdA

SIA

sampleA

SIClowstdC

SIC

highstdC

SIC

sampleC.

..

.*

..

SIAlow

A

SIA

sampleA

SIClow

C

SIC

sampleC

SIAlowA

SIA

highA

SIClowC

SIC

highC

10

Csample

IDENTYFYING UNCERTAINTY SOURCES

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

m

Cal. balanceCal.weights

Rep.

CIS

purity

Rep.

AREA S,STD,ISf d

Rep.

Cal. weights

Cal. balance

11

Csample

QUANTIFYING UNCERTAINTY SOURCES

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

12

UNCERTAINTY OF THE STANDARDS

2

concent

2

sol

solw

2

std

stdw

concent

u

w

u

w

uCuC

2

weights

2

rep

2

balanceweights uu2uu

solutionweight

stdConcstdweightC std.

13

UNCERTAINTY OF THE STANDARDS

balancetheof nCalibratio

weightingtheityrepeatibil

weightsthencalibratio

2

weights

2

rep

2

balanceweights uu2uu

2

conc

cu2

solw

solwu2

stdw

stdwuCcu

..

14

solutionweight

standardConcstdweightC gug

..)/

3

Uu valuecertC

.

15

0.6%

GRAVIMETRIC PREPARATION OF STANDARDSAmpoules SMR 2261

sol. INT 1 sol. INT 3

StandardBrack low

StandardBrack high

IS – sol. INT

IS solid

0.5%

0.6%

0.6%

0.6%

16

Csample

IDENTYFYING UNCERTAINTY SOURCES

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

m

Cal. balanceCal.weights

Rep.

CIS

purity

17

Csample

IDENTYFYING UNCERTAINTY SOURCES

CIS

Purity m

Cal. balanceCal.weights

Rep.

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

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PURITY OF THE INTERNAL STANDARD

The purity of IS is quoted by the supplier as 99.0 % . The quoted uncertainty is taken as a rectangular distribution

19

Rep.

AREA S,STD,IS

QUANTIFYING UNCERTAINTY SOURCES

Csample

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

m

Cal. balanceCal.weights

Rep.

CIS

purity

20

The uncertainties associated with the variability of the area were estimated by making replicate measurements of samples and bracketing standards. These uncertainties are estimated through the following equation:

n

reparea

su

UNCERTAINTY STANDARD OF THE SIGNAL

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UNCERTAINTY STANDARD OF THE SIGNAL

L o w s t d H i g h s t d S a m p l e

H C B A s t d A I S A s t d A I S A A I S

A m p . 1 1 5 , 9 8 1 7 , 0 5 4 4 , 9 2 1 7 , 7 8 2 2 , 7 2 1 6 , 6 3

A m p . 2 1 6 , 9 1 1 7 , 8 3 4 3 , 7 2 1 7 , 5 8 2 1 , 5 9 1 5 , 4 4

A m p . 3 1 5 , 1 7 1 6 , 5 0 4 8 , 1 0 1 8 , 6 6 1 9 , 2 4 1 3 , 9 6

H C B A l o w / A I S A h i g h / A I S A s a m p l e / A I S

A m p . 1 0 , 9 4 2 , 5 2 1 , 3 7

A m p . 2 0 , 9 5 2 , 4 9 1 , 4 0

A m p . 3 0 , 9 2 2 , 5 8 1 , 3 8

a v e r a g e 0 , 9 3 2 , 5 3 1 , 3 8S t a n d a r d d e v i a t i o n 0 , 0 1 0 , 0 5 0 , 0 2

u s t a n d a r d 0 , 0 0 8 0 , 0 2 7 0 , 0 2 7

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QUANTIFYING UNCERTAINTY SOURCES

Csample

m

Cal. balance

Cal.weightsRep.

Cstd

SMR

m

Cal. balanceCal.weights

Rep.

CIS

purity

Rep.

AREA S,STD,IS

dilution factor

Rep.

Cal. weights

Cal. balance

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CALCULATING THE CONCENTRATION

HCB Value (x)Standard uncertainty

u(x)

C low 20.71 0.059

C high 57.97 0.160

C IS (low ) 129.7 0.959

C IS (high ) 129.5 0.958

C IS (sample) 132.1 0.983

Dilution factor 1.10 0.00012

A low / A IS 0.93 0.008

A high / A IS 2.53 0.027

A sample/ A IS 1.38 0.027

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HCB: COMBINED UNCERTAINTYHCB A sample/ A low / A high / C low C high C IS low C IS high C IS fd

A IS A IS A IS samplevalue 1,38 0,93 2,53 20,71 57,97 129,70 129,5 132,1 1,10

uncertainty 0,009 0,008 0,027 0,059 0,160 0,96 0,96 0,98 0,00012

A sample/ A IS 1,38 1,39 1,38 1,38 1,38 1,38 1,38 1,38 1,38 1,38

A low / A IS 0,93 0,93 0,94 0,93 0,93 0,93 0,93 0,93 0,93 0,93

A high / A IS 2,53 2,53 2,53 2,56 2,53 2,53 2,53 2,53 2,53 2,53

C low 20,71 20,71 20,71 20,71 20,77 20,71 20,71 20,71 20,71 20,71

C high 57,97 57,97 57,97 57,97 57,97 58,13 57,97 57,97 57,97 57,97

C IS (low ) 129,7 129,70 129,70 129,70 129,70 129,70 130,66 129,70 129,70 129,70

C IS (high ) 129,5 129,49 129,49 129,49 129,49 129,49 129,49 130,45 129,49 129,49

C IS (sample) 132,1 132,15 132,15 132,15 132,15 132,15 132,15 132,15 133,13 132,15

fd 1,10 1,10 1,10 1,10 1,10 1,10 1,10 1,10 1,10 1,10

C sample 34,9 35,16 34,76 34,73 34,97 34,97 34,80 34,79 35,18 34,93

0,23 -0,16 -0,19 0,05 0,05 -0,12 -0,13 0,26 0,00

0,22 0,05 0,03 0,04 0,00 0,00 0,02 0,02 0,07 0,00

uncertainty(u) 0,47 49% 34% 41% 10% 11% 26% 28% 55% 1%

Incert. Exp. (U) 0,94RU (%) 2,70

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UNCERTAINTY CONTRIBUTIONS

Uncertainties in Determination of HCB

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50

A sample/ A IS

A low / A IS

A high / A IS

C low

C high

C IS (low )

C IS (high )

C IS (sample)

C sample

u (y,xi)

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CONCENTRATION AND UNCERTAINTY VALUES FOR THE SAMPLE SIM.8.P1.2

Meanng/g

Ung/g

RU%

Hexachlorobenzene 34.9 0.9 3gamma-HCH(g-BHC,lindane)

25.1 1.5 6

Heptachlor 17.2 1.6 9

Heptachlor epoxide 45.0 1.5 3

2,4'-DDE 53.8 4.2 8cis-Chlordane(alpha-chlordane)

85.6 3.0 3

trans-Nonachlor 75.3 4.4 6

Dieldrin 139 7.3 5

4,4'-DDE 513 28.9 6

2,4'-DDD 73.7 4.8 6

2,4'-DDT 25.4 1.2 5

4,4'-DDT 44.4 2.1 5

Mirex 26.7 0.7 3