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Characterization of CH3CCl3 Standards for Calibration in Environmental Monitoring

In 1996, CH3CCl3 scale with 4-5% additive in reagent was discovered. New standards were prepared with a new reagent in 2002, showing concentration-dependent differences from AGAGE at SMO and between NOAA MS and ECD. Standards prepared in 2003 improved characterization, with consistent responses. ECD and MS results are in agreement, enhancing CATS/Flask and CATS/AGAGE comparisons. Standards from SIO capillaries showed consistency, with one standard exhibiting a 3% lower response for unknown reasons.

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Characterization of CH3CCl3 Standards for Calibration in Environmental Monitoring

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  1. NOAA CH3CCl3 Scale • 1996 scale: discovered 4-5% additive in reagent • 2002 scale: prepared standards with new reagent • concentration-dependent offset from AGAGE at SMO • concentration-dependent difference between NOAA MS and ECD

  2. New standards prepared in 2003 SX-3518 20.7 ppt SX-3522 33.8 ppt SX-3519 40.8 ppt ALM-67682 60.5 ppt Standards prepared from SIO capillaries Primary Standards ALM-66844 616.6 ppb ALM-64461 607.7 ppb Consistent with each other. Response 1-2% lower than NOAA primaries (based on 80l GCMS analysis). Secondary Standards ALM-65174 38.6 ppt ALM-66027 78.4 ppt SX-3523 38.1 ppt

  3. Summary • New standards improve characterization of ECD response curve at low concentration. • ECD and MS results are consistent. • CATS/Flask and CATS/AGAGE comparison are improved. • Two of three standards made from SIO reagent are consistent with 2003 CMDL. • One shows 3% lower response (reason unknown).

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