U.S. EPA Ground Level Ozone Targets Released
New US EPA Ground Level Ozone Targets Released
If you’ve ever purchased high-end audio equipment, you’ve
most likely seen several columns of specification with a long lineup of
numerical values. IN some cases, bigger is better, in others, smaller numbers mean
improved quality. Along with total audio bandwidth, one of the most important
values is the Signal to Noise Ratio (SNR).
SNR, as is implicit in its name, evaluates an amplified broadcast signal
or recorded snore signal against the background noise that the equipment itself
creates. In this case, the bigger the SNR, the reduced amount of distortion,
and thus the greater the sound output is to a live performance. SNRs have
always been necessary to measure
instrumentation output as well. Currently, with growing demand on the detection
limits of gas chromatography and mass spectrometry, getting rid of response noise
has become more vital than it ever has been before. Now is the time to attempt
to reduce or eliminate the sources of this noise wherever possible.
In past weeks, the U.S. EPA released its new ground level
ozone target of 70 parts per million (ppm). Reaching this threshold limit will
call for a significant increase in atmospheric testing for volatile organic
compounds (VOC) in several areas that had not previously required monitoring.
Depending on the demographic area, air sampling for sixty or more contaminants
will be administered , with special highly-accurate multi-component mixtures of
these volatile chemicals used to determine a baseline. Two different mixtures
are available, with the concentrations of these components falling into two
ranges, either a high range around 1 ppm or a lower range mixture of components
at 100 parts per billion (ppb).
As you might imagine, carrier gases now become an essential
component of any plan to boost SNR. And because these gases are not supplied by
the instrument provider, they can frequently be critiqued the most when
questions surface. Where once “commodity type” specialty gas grades like “Zero,”
“Pre-Purified,” or “Ultra-High Purity,” could be acceptable for component
detection as low as 500-1000 ppm, Continuous Emmissions Monitoring (CEM) now
requires something better. In this case, better means certified lower levels of
impurities, with analytical certification of their actual concentration, along
with proper cylinder preparation to reduce wall off-gassing, and to minimize
atmospheric contamination while under vacuum. Discharging of these gases also necessitates
the right pressure pressure reduction device , again lowering contamination of
the system through routine cleaning and assembly, and the proper choice of
materials that will not react with the sample stream.
So what to do? Insist on carrier gases that reduce
distortion and provide as flat a baseline as is practical for the application.
If analytical requirements mandate accuracy below 10 parts per million, utilize
the best available carrier gases. Look
for secondary purification as part of the packaging process, either by
absorption media or cryogenic distillation. Inquire about cylinder preparation,
as the gas is only as good as the container its held in. Also ask about record
keeping and the accuracy of the reference standards, again because a low level
oxygen impurity report means nothing if the instrument isn’t properly
calibrated, or the calibration gas has no traceability to a defined standard.
Gases such as PurityPlus® Grade 6.0
Helium and Ultra Zero Air, with full certificates of analysis, can feasibly
satisfy the needs of an increasingly precise world. Try them, you’ll be well
October 14, 2015