| Regardless of how you use specialty gas
| |
| | at the bottom of the traceability
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| mixtures to calibrate a
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| | hierarchy. A GMIS introduces more
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| laboratoryinstrument or monitor, the most
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| | uncertainty because more steps are
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| important thing you can do to ensure the
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| | involved and because NIST is not involved
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| accuracy of your measurements is to
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| | in either their analysis or
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| ensure the accuracy of your gas mixture.
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| | certification. The gas supplier is
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| Gas mixture accuracy, in turn, is largely
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| | responsible for assigning the
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| dependent upon its analytical
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| | concentration and accuracy, based solely
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| traceability to a reference material. For
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| | on their analysis.
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| analytical traceability to exist, there
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| | Gas mixtures that are produced using
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| must be an unbroken link of comparison
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| | GMISs do not provide direct
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| between the measured value of the gas
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| | NIST-traceability, and so may not be
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| mixture and a reference that is
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| | suitable for some applications. For
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| recognized in the national or
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| | example, the EPA requires that a
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| international measurement system as being
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| | Continuous Emission Monitor be calibrated
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| a true value. Thus, analytical
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| | using a protocol that is at least as
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| traceability is the link between the
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| | accurate to within ±2%. Use of a
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| analyzed concentration and the true
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| | protocol that was prepared using a GMIS
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| concentration of a gas mixture. The
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| | may not guarantee such accuracy.
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| National Institute of Standards and
| |
| | When selecting any specialty gas mixture,
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| Technology (NIST) provides Standard
| |
| | be sure you know what type of standard
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| Reference Materials (SRMs) for this
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| | the mixture you are purchasing will be
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| purpose. Another such metrological
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| | analyzed against. To ensure accuracy,
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| organization, the Netherlands Measurement
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| | insist on traceability to an SRM, PRM or
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| Institute (NMi), provides Primary
| |
| | NTRM. Also remember that, as in the case
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| Reference Materials (PRMs).
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| | of emission monitoring, traceability and
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| Analytical traceability is achieved by
| |
| | subsequent accuracy may be governed by
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| laboratory analysis of a mixture using an
| |
| | law.
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| instrument that has been directly
| |
| | You can ensure the integrity of your
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| calibrated using either an SRM or a PRM.
| |
| | laboratory calibrations by obtaining gas
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| A mixture analyzed in this manner is said
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| | mixtures from reliable companies such as
|
| to be "directly traceable." SRMs and PRMs
| |
| | Scott Specialty Gas, which has been the
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| are at the top of the traceability
| |
| | leading supplier of precursor standards
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| hierarchy and add the least amount of
| |
| | for NIST SRMs for more than 25 years,
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| uncertainty to a mixture analysis because
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| | Praxair, the second largest supplier of
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| they are individually analyzed and
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| | industrial and specialty gases to
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| certified by NIST or NMi laboratories.
| |
| | chemical companies worldwide, and Airgas,
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| Since 1995, NIST and NMi have maintained
| |
| | which offers an extensive line of high
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| an equivalence agreement in those cases
| |
| | purity specialty gases as well as a full
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| where comparative analyses have been
| |
| | range of specialty gas equipment
|
| completed by the two labs. Because of
| |
| | specifically designed for use with
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| this NIST/NMi equivalency, traceability
| |
| | highest purity gases and high tolerance
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| to a PRM is considered the legal
| |
| | gas mixtures. Your dedication to accurate
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| equivalent of an SRM.
| |
| | calibrations will be rewarded many times
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| Direct analytical traceability can also
| |
| | over in the precision of your
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| be established using what are known as
| |
| | measurements, and thus the quality of
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| NIST Traceable Reference Materials
| |
| | your products, which can only make your
|
| (NTRMs). NTRMs are produced by gas
| |
| | customers smile.
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| suppliers and then batch analyzed and
| |
| | For more information about EPA protocol
|
| audited by NIST against the same internal
| |
| | gas accuracy, download a copy of Accuracy
|
| standards as SRMs. NTRM values are
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| | Counts from
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| assigned by NIST and offer nearly the
| |
| | This article is provided by Scott
|
| same accuracy confidence level as SRMs
| |
| | Specialty Gases. Scott Specialty Gases, a
|
| and PRMs in most cases.
| |
| | leading global manufacturer of specialty
|
| The high cost of producing SRMs and PRMs
| |
| | gases located in Plumsteadville, PA. More
|
| make it economical for some specialty gas
| |
| | information on the company can be found
|
| suppliers to blend intermediate standards
| |
| | at
|
| called Gas Manufacturer Intermediate
| |
| | This article is copyrighted by Scott
|
| Standards (GMISs). Though they are
| |
| | Gases.
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| analyzed against existing SRMs, they are
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| |
|
