1. Ensuring of Traceability
Wolfgang Garche
Saxony-Anhalt Environmental Protection Agency
Department Air Quality Monitoring, Information, Assessment

2. 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.

3. Traceability is characterized by a number of essential elements:
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).

4. Laboratory reference standards
Traceability chain:
BIMP
comparisons on international level
NMI
NRL
RCL
Measuring site
National standards
Reference standards
Laboratory reference standards
analysers
comparison
measurements
comparison
measurements/
certification
comparison
measurements
transfer standards
comparison
measurements/
certification
calibration

5. Comparison measurement:
reference standard
Traceable
SO2: 1,2 ppb
Reference
Analyser
measurements
calibration
a series of 1 to N measurements
Test gas
Ctest gas
Uncertainty should be stated in the certificate of the reference standard

6. 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

7. Certification of span gases produced by permeation:
Measurement of the total gas flow (span gas flow + bypass flow):
determination of the permeation rate:
permeation
cell
Span gas
Bypass
Zero gas

8. Ozone measurement by direct UV-photometry:
Optical path length L UV
Measurement
Detector
253,7 nm
Hg-lamp
p, T
Pressure and temperature sensors P
Pump
Ozone-Generator
ZERO SPAN
Lambert-Beer‘s law
e - Absorption coefficient of O3 at 253,7 nm
= 308 atm-1cm-1 (273 K, 1013 hPa)
Zero gas  measurement of I0
Span gas  measurement of I

9. Use of an ozone monitor as UV-reference meter:
(O3 41 M-LCD, O3 42 M)
Optical bench
Ozone-Generator
ZERO SPAN
I :
I :
Raw : 0,00
Aver. : 0,00
Optical T° = 42,3°C
Internal T° = 36,6°C
T° LamP = 54,6°C
Flow rate =1888
Pressure =1001mb
I LamP = 32mA
 = absorption coefficient of O3 at 254 nm = 308 atm-1 cm-1 at 273 K and 1013 hPa
L= optical path length in cm
T= gas temperature in °C
p= gas pressure in hPa
p, T
This method can be used for the certification of ozone test gases!
Optical bench

10. Needed equipment in order to ensure traceability:
NO reference
standard
Reference Analysers
UV-photometer
NO 1,2 ppb
NOx: 1,2 ppb
NO2 0,0 ppb
19500
20,3 T
998 P
SO2 reference
standard
SO2: 1,2 ppb
CO reference
standard
CO: 1,0 ppm
Data acquisition
system
Zero
air
generator
Ozone-Generator
ZERO SPAN
(TE49PS + O3-analyser)

11. Many Thanks
for your Attention!