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Abstract

For an intercomparison programme among 29 continuous SO-2 analyzers in the EC, cylinders of air - SO-2-mixtures were used as comparison standards. Two or three samples of two batches for each participating Member State were measured successively by the Central Laboratory (CL) of the JRC Ispra, calibrating with the TCM reference method of the Directive, and by one or more National Laboratories (NL) using their own calibration methods. Regular checks of the mixtures carried out by the CL showed an exponential decay of SO-2 concentrations. In the two batches (respectively 190 ppb and 40 ppb levels) mean losses of 0.48% and 3.7% per month were found with coefficients of variation of 28% and 48%. The CL values were corrected from the SO-2 decays and a statistical analysis was performed between NL and CLm, CLm being the corrected CL concentrations at the measuring month of NL. 68% of the 186 NL-CLm crosschecks showed comparability ( +-6.3%) versus the CL reference standard. This standard, a calibration curve plotted with 5 permeation tubes, showed differences lower than 2.5% versus the TCM method. Considering separately (LI) and network instruments (NI), the range of comparability included 73% NI and only 40% LI crosschecks. Out of this range a bad linearity of conductimetric and coulometric instruments was noticed.

Additional information

Authors: PAYRISSAT M, JRC ISPRA ESTAB. (ITALY);RAU H, JRC ISPRA ESTAB. (ITALY);SERRINI G JRC ISPRA ESTAB. (ITALY), JRC ISPRA ESTAB. (ITALY)
Bibliographic Reference: 4TH EUROPEAN SYMPOSIUM ON PHYSICO-CHEMICAL BEHAVIOUR OF ATMOSPHERIC POLLUTANTS, STRESA (ITALY), SEPT. 23-25, 1986 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32846 ORA
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