BS/EN 16909-2017 pdf download.Ambient air – Measurement of elemental carbon ( EC ) and organic carbon ( OC ) collected on filters.
The field and laboratory blank values (covered in Clause 10) generally show that a certain amount of organic substance is bound to the quartz fibre filter and may accumulate on a filter by mechanisms other than the active sampling. To reduce positive artefacts, samples shall be kept and handled away from any contamination sources. e.g. organic liquids or aerosols.
9.4 Analysis
Known factors which influence the analysis are summarized below:
— Carbonate carbon (CC) will interfere with the organic carbon and/or the elemental carbon fraction. If the filter punch subjected to analysis is still coloured after the analysis is finished, a significant inorganic material content (soil/crustal material) can be suspected, and therefore inorganic carbon interference is possible.
— Possible methods for assessing carbonate carbon are given in Annex C. No recommendations on how often the CC assessment has to be performed can currently be given. Policies for the frequency and timing of CC assessment are left to the responsible personnel. The results of the analysis shall not be subtracted from the EC and/or OC measurement values but recorded to allow the estimation of possible interferences.
— Light absorbing organic carbon can affect the laser correction as these species are removed from the filter or pyrolyzed during He mode, causing changes in transmittance.
— Certain elements (e.g. Na and K), which can be present either as contaminants in the filter or as part of the deposited material, have been shown to catalyse the removal of EC at lower temperatures, thus affecting the thermal evolution of EC. This interference may be reduced by choosing filters with low alkali metal contents.
— Oxygen donating species in the samples may interfere with the EC and OC analysis. Filters that remain coloured after the analysis may be an indication of the presence of FeOas such species.
10 Quality assurance/quality control (QA/QC)
10.1 QA/QC for sampling parameters
QA/QC for parameters such as sampled volume, size fraction, and losses of semi-volatiles shall be performed by following the relevant procedures specified in EN 12341:2014, and other procedures described in Clauses 7 and 8.
10.2 Field blank determination
— to check that the laboratory environment and laboratory procedures in use do not introduce significant OC and/or EC contamination, either from material collected onto the blank filters, or from contamination within the instrument.
These purposes will generally be addressed in parallel.
The requirement for initially assessing whether a specific filter type is suitable for EC and OC monitoring is described in 6.1.
Alongside the filter checks given In 6.1, the laboratory procedures and environment will be checked by analysing laboratory blanks. It is recommended that laboratory blanks are analysed at least once each working week, or when very high fIeld blank concentrations are found.
Details of the laboratory blank procedures are left to the responsible personnel. These procedures shall he recorded together with the analytical data for the laboratory blanks.
10.4 Calibration for TC
Because there are no traceable primary reference materials available for atmospheric EC and OC, calibration is currently limited to TC.
The principal calibration of the analytical system can be conducted via TC values provided by blank filter samples spiked with calibration solutions of pure organic compounds such as sucrose. Further information is given in Annex B and in the analytical instrument user’s manual. The instrument shall be regularly calibrated for TC at least once every 12 months and after any major maintenance or modification of the system.
The calibration shall be checked at least every measurement day (e.g. by analysis of a control filter — see 10.6.1 and/or sucrose spiked filter) with a quantity of TC relevant to the quantities In the field samples being analysed. The results shall be within ± 10 % or ± 0,5 pg C/cm2 of the expected value, whichever is greater. If not, the reasons have to be investigated (see Annex B) and the result of the investigation shall be recorded with the other analytical data.
10.5 Long term stability and repeatability
The long term stability of the analytical system shall be determined from control filter measurements (see 10.6.1) and from the spiked filter calibrations. A TC and OC long term stability of 10 % or ± 0,5 pg C/cm2. whichever is greater, difference from the initial mean of the first ten measurements can be viewed as sufficient. An EC long term stability of 15 % or ± 0,5 pg C/cm2 difference, whichever is greater, from the initial mean of the first ten measurements can be viewed as sufficient.
The repeatability is calculated as the relative standard deviation of ten measurements of the control filter being conducted during one day. An accepted value for repeatability is 5 % or ± 0,5 pg C/cm2 difference, whichever is greater. The instrument shall be regularly assessed for repeatability at least once every 12 months and after any major maintenance or modification of the system.BS/EN 16909-2017 pdf download.