Traceability 1 Saxony-Anhalt EU Twinning RO 04/IB/EN/09 State Environmental Protection Agency...

Traceability

1 Saxony-Anhalt EU Twinning RO 04/IB/EN/09State Environmental Protection Agency Wolfgang Garche Bukarest

Wolfgang Garche

Saxony-Anhalt Environmental Protection AgencyDepartment Air Quality Monitoring, Information, Assessment

Ensuring of Traceability

Traceability


Definition of Traceability(International Vocabulary for Metrology)

Property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.

Why is traceability required?If decisions based on analytical results are made, these results must be “good” and “reliable”. A key property of such results is comparability, that means the ability to compare results without references to its origin.

Traceability


• an unbroken chain of comparisons going back to a standard acceptable to the parties, usually a national or international standard;

• the measurement uncertainty for each step in the traceability chain must be calculated according to defined methods and must be stated so that an overall uncertainty for the whole chain may be calculated;

• each step in the chain must be performed according to documented and generally acknowledged procedures; the results must equally be documented;

• the laboratories or bodies performing one or more steps in the chain must supply evidence for their technical competence (e.g. by demonstrating that they are accredited);

• the “appropriate” standards must be primary standards for the realization of the SI units (if applicable);

• calibrations must be repeated at appropriate intervals; the length of these intervals depends on a number of variables, (e.g. uncertainty required, frequency of use, way of use, stability of the equipment).

Traceability is characterized by a number of essential elements:

Traceability


RCLNMI NRL

National standards

Reference standards

Laboratory reference standards

comparisonmeasurements

comparisonmeasurements/

certification

BIMP

transfer standards

com

paris

onm

easu

rem

ents

comparisons on international level

Measuring site

analysers

calibration

Traceability chain:

comparisonmeasurements/

certification

Traceability


SO2: 1,2 ppb

Tra

ceab

lere

fere

nce

st

and

ard

calibration

Refu

Tes

t g

as

measurementsReference Analyser

Comparison measurement:

Ctest gas

Uncertainty should be stated in the certificate of the reference standard

2Ref

2Ref

2

2c

c

c

u

cN1

1s

c

uU(c)

a series of 1 to N measurements

Traceability


Reference analyser:

Selected analyser with good performance characteristics (should be type approved in compliance with the EN standards)

Only used for test gas measurements (never for measurements of ambient air)

Must be under control (daily zero and span check, periodical calibrations and checks, quality control charts)

Operation under defined ambient conditions Known measurement uncertainty

Traceability


permeation cell

Δt

ΔMP

determination of the permeation rate:

Measurement of the total gas flow (span gas flow + bypass flow):

V

PC Span

Zero gas

Span gas Bypass

Certification of span gases produced by permeation:

Traceability


UV 253,7 nm

Hg-lamp

Measurement Detector

Optical path length L

p

1013

273

T273

I

Iln

Lε

10ppmc 0

6

O3

][

Lambert-Beer‘s law

Absorption coefficient of O3 at 253,7 nm

= 308 atm-1cm-1 (273 K, 1013 hPa)

Ozone measurement by direct UV-photometry:

p, TPressure and temperature sensors

Ozone-Generator

ZERO SPAN

P Pump

Zero gas measurement of I0

Span gas measurement of I

Traceability


Use of an ozone monitor as UV-reference meter:

p, T

Optical bench

Ozone-Generator

ZERO SPAN

Optical bench

I0 : 00985432I : 00985432

Raw : 0,00Aver. : 0,00

Optical T° = 42,3°C Internal T° = 36,6°CT° LamP = 54,6°C

Flow rate =1888Pressure =1001mbI LamP = 32mA

p

T

I

I

LcO

1013

273

273ln

10 06

3

= absorption coefficient of O3 at 254

nm = 308 atm-1 cm-1 at 273 K and 1013 hPa

L= optical path length in cmT= gas temperature in °Cp= gas pressure in hPa

(O3 41 M-LCD, O3 42 M)

This method can be used for the certification of ozone test gases!

Traceability


CO: 1,0 ppm

SO2: 1,2 ppb

NO 1,2 ppbNOx: 1,2 ppbNO2 0,0 ppb

Zeroair

generator

NO

re

fere

nc

e s

tan

da

rd

SO

2 r

efe

ren

ce

sta

nd

ard

CO

re

fere

nc

e s

tan

da

rd

Ozone-Generator

ZERO SPAN

Reference Analysers

Data acquisition system

19500

20,3

T

998

P

UV-photometer

Needed equipment in order to ensure traceability:

(TE49PS + O3-analyser)

Traceability


Many Thanks

for your Attention!

Traceability 1 Saxony-Anhalt EU Twinning RO 04/IB/EN/09 State Environmental Protection Agency...

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