Wolfgang Garche Saxony-Anhalt Environmental Protection Agency

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

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

5. Traceable reference standard SO2: 1,2 ppb Comparison measurement: 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. Span gas Bypass 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 Zero gas

8. Ozone-Generator ZERO SPAN P Ozone measurement by direct UV-photometry: Optical path length L UV Measurement Detector 253,7 nm Hg-lamp p, T Pump Pressure and temperature sensors 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. Ozone-Generator ZERO SPAN Use of an ozone monitor as UV-reference meter: (O3 41 M-LCD, O3 42 M) Optical bench I0 : 00985432 I : 00985432 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 methodcan be used for the certification of ozone test gases! Optical bench

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

11. Many Thanks for your Attention!