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EUROMET/METCHEM comparison PCB congeners in organic solution F. Ulberth
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PCBs Belong to 12 POPs (UNEP) Minimisation and phase-out programmes:
Basel Convention OSPAR Convention: close to zero concentrations in the marine environment Convention on the protection of the marine environment of the Baltic Sea Area UNECE POPs Protocol to the Convention on long- range transboundary air pollution: to reduce the emissions of POPs Stockholm Convention (POPs Convention)
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Background - EU Community strategy for dioxins, furans and polychlorinated biphenyls (COM(2001) 593 final) Measurement methods and standards: …in order to obtain comparable, consistent, reliableand high quality measurement results it is necessary toimplement a high quality measurement standard at Community level.
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Suite of congeners studied
IUPAC Congener PCB 28 2,4,4’- Trichlorobiphenyl 52 2,2’,5,5’- Tetrachlorobiphenyl 101 2,2’,4,5,5’- Pentachlorobiphenyl 118 2,3’,4,4’,5- Pentachlorobiphenyl 138 2,2’,3,4,4’,5’- Hexachlorobiphenyl 153 2,2’,4,4’,5,5’- Hexachlorobiphenyl 180 2,2’,3,4,4’,5,5’- Heptachlorobiphenyl
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Sample distribution 30 Nov 04 by courier service
four ampoules of IRMM solution ( ng/g each) four ampoules of LGC solution ( ng/g each, in addition 8 other congeners) Electronic reporting sheet Reporting requirements: independent duplicates from three ampoules (in ng/g), uncertainty estimate, details of analysis Deadline: 15 Jan 05
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Participants and techniques
Institute Technique IS Calibration Uncertainty budget IRMM (EC) GC-MS labelled crystalline Yes LGC (UK) IMGC (IT) external BCR solution BAM (DE) NIST solution LNE (FR) VNIIM (RU) LGC Promochem UKRCSM (UA) SUPELCO solution No VITUKI (HU) JORDFORSK (NO) internal EHRENSTORFER solution
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Capillary columns HP-5MS + DB-35MS (60 m x 0.25 mm)
DB-XLB (30 m x 0.25 mm) HT-8 (50 m x 0.22 mm) poly(5%diphenyl/95%dimethyl)siloxane (30 m x mm) DB-17MS (60 m x 0.25 mm) VF-5ms (30 m x 0.25 mm) HT-8 (40 m x 0.18 mm) RTX5MSi (30 m x 0.25 mm)
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IRMM solution – PCB28
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LGC solution – PCB28
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IRMM solution – PCB52
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LGC solution – PCB52
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IRMM solution – PCB101
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LGC solution – PCB101
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IRMM solution – PCB118
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LGC solution – PCB118
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IRMM solution – PCB138
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LGC solution – PCB138
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IRMM solution – PCB153
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LGC solution – PCB153
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IRMM solution – PCB180
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LGC solution – PCB180
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%-Deviation from known IRMM values
LGC BAM LNE UKCR SM Jord- forsk VITUKI VNIIM PCB 28 -5.9 2.0 0.0 -12.5 -44.3 -21.0 -20.2 -6.0 PCB 52 -3.0 1.8 -0.4 -8.1 -24.6 -17.2 -17.1 -9.5 PCB 101 -4.7 0.1 -2.6 -10.8 -25.0 -18.1 -14.2 PCB 118 -3.8 2.1 -6.4 -57.1 -30.7 -16.0 -16.7 PCB 138 -1.4 2.9 1.4 -29.2 -28.8 -10.2 -11.6 PCB 153 0.8 0.6 -8.7 -18.3 -9.8 -12.7 -8.4 PCB 180 1.9 1.5 -1.6 -15.7 -22.2 -22.6 -12.6 -6.9
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Reported uncertainties vs repeatability IRMM solution
LGC BAM LNE VNIIM 2*sd U PCB 28 1.7 2.1 0.5 0.6 0.7 0.8 1.4 0.4 0.9 PCB 52 1.8 2.4 1.0 2.0 3.1 PCB 101 2.3 3.4 1.9 2.2 3.7 PCB 118 3.2 1.1 2.6 6.4 1.2 5.3 PCB 138 3.9 1.3 2.5 PCB 153 1.5 PCB 180 0.2 U – expanded uncertainty (95 %)
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Reported uncertainties vs repeatability LGC solution
IRMM LGC BAM LNE IMGC VNIIM 2*sd U PCB 28 17.7 37.5 5.2 6.3 58.7 59.0 54.4 31.8 --*) -- 7.0 13.9 PCB 52 9.7 27.6 4.2 6.8 51.7 53.8 47.1 45.3 44.4 83.0 6.6 11.4 PCB 101 19.2 40.5 5.8 11.1 28.3 31.0 24.6 39.3 70.9 14.7 PCB 118 15.7 33.8 4.4 9.9 56.7 90.2 18.3 28.1 134.2 80.6 9.6 20.9 PCB 138 14.5 35.3 9.2 34.5 36.6 32.6 31.5 105.6 69.0 15.9 PCB 153 14.1 31.3 3.1 8.2 26.9 27.2 27.9 38.8 12.2 18.6 PCB 180 21.6 36.8 5.7 12.8 30.6 33.2 71.4 79.0 71.6 8.8 21.4 U – expanded uncertainty (95 %) *) co-eluting substances
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IRMM uncertainty budget
expanded uncertainty k coverage factor (k=2) c average concentration of the analyte u(cst) uncertainty of standards used (purity, mass) RSDRF relative standard deviation of response factor determined n number of standards used for RF determination RSDresult relative standard deviation of results (analyte concentration)
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LGC uncertainty budget
Measurement equation wi: mass fraction of PCB in sample X wZ: mass fraction of PCB in primary standard Z mY: mass of spike Y added to the sample X to prepare the blend B (=X+Y) mX: mass of sample X added to the spike Y to prepare the blend B (=X+Y) mZc: mass of primary standard solution Z added to the spike Y to make calibration blend Bc (=Y+ Z) mYc: mass of spike Y added to the spike Y primary standard solution Z to make calibration blend Bc (=Y+ Z) R’B: measured isotope amount ratio of sample blend (X+Y) R’Bc: measured isotope amount ratio of calibration blend (Bc=Z+Y) wi: mass fraction of the individual measurement results : average of the 6 individual mass fractions n: number of individual values averaged (here n = 6)
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BAM uncertainty budget
Major contributions to the combined uncertainty of the mean: precision of the method concentration of the calibration solution standard deviation of the six replicates taken as method precision (includes precision associated weighing the sample, spiking and calibration etc) expanded uncertainty of NIST SRM-1493 divided by 2 standard deviation of replicate measurements and standard uncertainty of the calibration standard combined (the 1/sqr(n) reduction was not applied) coverage factor k=2 for expanded uncertainty
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LNE uncertainty budget
Uncertainty estimation (GUM compliant) using WINCERT software taking into account: Masses Uncertainty concentration of SRM used for calibration Uncertainty of compound purity Ratio measurement in sample Ratio measurement in standard Fidelity
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IMGC uncertainty budget
Contributions to combined standard uncertainty: calibration curve repeatability of readings of sample measurements calibration curves determined by Weighted Least Squares
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VNIIM uncertainty budget
Contributions to combined standard uncertainty RSD of calibration solution standard uncertainty of gravimetric preparation of standard solution standard uncertainty of gravimetric preparation of sample solution RSD of response factor RSD of the mean of the six individual results
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Conclusions Agreement of results among participants not fully satisfactory Agreement of individual results with gravimetric preparation values not fully satisfactory Not all participants provided uncertainty budgets Harmonisation of uncertainty budgets necessary
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Outlook Option 1: Repeat comparison on new set of PCBs in organic solution Option 2: Repeat comparison on new set of PCBs in organic solution plus common quality control sample (either “old” IRMM or LGC solution) Option 3: Repeat comparison on new set of PCBs in organic solution plus (i) common quality control sample (either “old” IRMM or LGC solution) and (ii) extract of real sample (soil / sludge)
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