Wednesday, October 17, 2018

An Improved Method for the Analysis of ppt Levels of Mercury in Ambient Air

Assignment Status:AssignedSession Title:ACS (American Chemical Society) Poster Session
Session Date03/17/2019Starting Time:( Slot # 25 )
SUNDAY POSTERS: 3:30pm-7:30pm Author(s) present 5:30pm-7:30pm Location: Pub Pittcon, Pennsylvania Convention Center, Philadelphia, PA

Authors: Driscoll and Maclachlan
A method for the analysis of ppb levels of mercury using a photoionization detector (PID) with a 10.6 eV lamp was described several years ago. The ionization potential for Hg is 10.43 eV, so it responds to the PID. A new gold film in the preconcentrator was used to collect and concentrate the Hg vapor from the air.

The system is purged at 200 degrees C to remove any water vapor and/ or VOC’s from the gold film. This also improves the selectivity of the PID since all VOC’s which would respond are removed. Then the gold film is rapidly heated to 550 degrees C to remove the Hg.
We have decreased the volume of the preconcentrator by more than an order of magnitude and changed the heating method. Instead of a cartridge heater we are using an RF heater. We are now able to heat the low mass concentrator at ten times the speed. This gives us a much sharper peak and a much faster cool down time. We have improved the detection limit for Hg from about 10 ppb to < 1 ppb and with a reasonable sampling time, we can achieve < 1 ng/m3 which is a typical number for ambient air.

Tuesday, October 16, 2018

Fast GC PID & FUV Detectors for Measurement of Greenhouse Gases in Livestock Barns

Assignment Status:AssignedSession Title:Analytical Agricultural Applications (Half Session)
Session Date03/17/2019Starting Time:03:05 PM ( Slot # 1 ) 

Authors: Driscoll and Maclachlan
Carbon dioxide, methane, and nitrous oxide are important greenhouse gases. In fact, methane is the second largest anthropogenic greenhouse gas (GHG), that contributes 14% of total anthropogenic GHG emissions estimated in 2004. Agricultural emissions of methane account for about 60% of the total methane from anthropogenic sources, of which 25% arises from fermentation in livestock. A considerable effort is underway to modify the diets of livestock to reduce methane emissions. A rapid analysis of these components is necessary to accurately measure these components. A considerable amount of ammonia is present and that should be measured.

One potential solution to this dilemma is to utilize fast GC columns with a low mass in a portable GC like the PID Analyzers Model GC312. What is a FAST GC column? There are several types: One approach involves using a 25m x 0.32 mm ID, 0.25┬Ám film thickness that is resistively heated and can be programmed at a much higher rate than conventional ovens. It can also be cooled faster since it has a very small thermal mass. This is the approach that we have taken. The detectors used would be a Far UV Absorbance detector (FUV) for carbon dioxide, methane and nitrous oxide and a PID for measuring ammonia. A complete analysis of these gases can be done in about 3 minutes. This method will provide better detection limits and more accurate results than conventional spectroscopic methods.

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