LOGOS - NOAA Global Monitoring Laboratory
Source: https://gml.noaa.gov/hats/flask/flasks.html
Archived: 2026-04-23 17:33
LOGOS - NOAA Global Monitoring Laboratory
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Global Monitoring Laboratory
HATS Flask Sampling Program: A brief history and current status
HATS has been analyzing air samples collected in flasks since 1977. Originally set up under the auspices of the Geophysical Monitoring for Climatic Change (GMCC) division of NOAA's Air Resources Laboratory (NOAA/ARL), this program initially involved the analysis of flask samples from only five remote sites in both hemispheres: Point Barrow,
Originally, air was collected weekly in pairs in 300-ml electropolished, stainless-steel flasks (from Whitey with Nupro SS-4H metal bellows valves) filled to 1.5 atm with a metal bellows pump to minimize contamination of CFC's by plastics or other elastomers. All samples were analyzed for N
2
O, CFC-11, and CFC-12 in the Boulder labs on a Hewlett Packard 5710A, electron-capture gas chromatograph (GC/ECD) equipped with a Porasil A column.
In late 1991, HATS began analyzing flask samples for hydrochlorofluorocarbons (HCFC's), hydrofluorocarbons (HFC's), and other halogenated trace gases by gas chromatography with detection by mass spectrometry (GC/MS, the M1 instrument. Chromatographic analysis is performed on a 60m DB-5 column with cryotrapping of the air samples). To allow for this additional analysis, larger electropolished stainless-steel flasks (2.4-L flasks Max Planck Institut für Chemie, Mainz, and 3-L flasks from Lab Commerce, USA) were circulated to the sample sites. These flasks were found to store a number of trace gases more reliably than the smaller 850 ml flasks and enabled, along with the development of the GC/MS instrument, reliable measurements of a number of additional gases by the mid-1990s.
In 1997, the M1 GCMS was fully automated to allow the analysis of flasks and standards through the night. This involved remaking the sample handling box with new devices for automatically controlling flow from a manifold of different flasks and standards. Peak integration was also automated through a custom program running in Excel. These changes increased the efficiency and precision of the measurements and enabled many more flasks to be analyzed in the program.
By early 2000s, glass flasks were also circulated to some HATS sampling sites. These glass flasks are identical to those used by the NOAA carbon cycle group (they have glass pistons and Teflon o-ring seals). Glass flasks are circulated to a subset of sites for three main reasons. First, they allow reliable measurements of a number of gases that degrade when stored in stainless steel flasks, particularly at dry locations and when the delay between sampling and analysis is long. For example, reliable flask measurements of methyl bromide, bromoform, methyl iodide, carbonyl sulfide, and other gases are only possible at the South Pole from glass flasks. Secondly, glass flasks allow us to determine if results for many gases are independent of flask type (e.g., at CGO and SPO). At some sites, however, only glass flasks are used (PSA, SUM, WIS, and, initially, WLG). Finally, glass flasks allow sampling at new sites for much lower start-up costs than if stainless steel flasks were used. This has been an important factor in us being able to increase the number of sampling sites in our network has in recent years. The main downside of using glass flasks is that they prevent reliable measurements of specific compounds owing to contamination, probably related to the Teflon o-rings and the chemicals they came in contact with during manufacture. In the 1980s this contamination was observed for CFC-113; since then we have observed enhanced levels of HCFC-141b, and C
2
Cl
4
in glass flasks.
In mid-2006 measurements from LEAPS were stopped. Continuity of measurements was provided for three halons by the GCMS (M1) analysis of flasks. While two of the halons could be measured readily by the GCMS in its existing configuration, it was possible for H-1301 during 2006 and 2007 only by reanalyzing flasks with a short plug of ascarite in the sample stream (not the typical configuration). Ascarite removed CO
2
from the sample air stream and allowed quantitative analysis of more volatile gases free from the multiple matrix effects (in the transfer of condensed sample to the column, and in the mass spectrometer.
Skip to main content
An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov
website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or
https://
means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Global Monitoring Laboratory
HATS Flask Sampling Program: A brief history and current status
HATS has been analyzing air samples collected in flasks since 1977. Originally set up under the auspices of the Geophysical Monitoring for Climatic Change (GMCC) division of NOAA's Air Resources Laboratory (NOAA/ARL), this program initially involved the analysis of flask samples from only five remote sites in both hemispheres: Point Barrow,
Originally, air was collected weekly in pairs in 300-ml electropolished, stainless-steel flasks (from Whitey with Nupro SS-4H metal bellows valves) filled to 1.5 atm with a metal bellows pump to minimize contamination of CFC's by plastics or other elastomers. All samples were analyzed for N
2
O, CFC-11, and CFC-12 in the Boulder labs on a Hewlett Packard 5710A, electron-capture gas chromatograph (GC/ECD) equipped with a Porasil A column.
In late 1991, HATS began analyzing flask samples for hydrochlorofluorocarbons (HCFC's), hydrofluorocarbons (HFC's), and other halogenated trace gases by gas chromatography with detection by mass spectrometry (GC/MS, the M1 instrument. Chromatographic analysis is performed on a 60m DB-5 column with cryotrapping of the air samples). To allow for this additional analysis, larger electropolished stainless-steel flasks (2.4-L flasks Max Planck Institut für Chemie, Mainz, and 3-L flasks from Lab Commerce, USA) were circulated to the sample sites. These flasks were found to store a number of trace gases more reliably than the smaller 850 ml flasks and enabled, along with the development of the GC/MS instrument, reliable measurements of a number of additional gases by the mid-1990s.
In 1997, the M1 GCMS was fully automated to allow the analysis of flasks and standards through the night. This involved remaking the sample handling box with new devices for automatically controlling flow from a manifold of different flasks and standards. Peak integration was also automated through a custom program running in Excel. These changes increased the efficiency and precision of the measurements and enabled many more flasks to be analyzed in the program.
By early 2000s, glass flasks were also circulated to some HATS sampling sites. These glass flasks are identical to those used by the NOAA carbon cycle group (they have glass pistons and Teflon o-ring seals). Glass flasks are circulated to a subset of sites for three main reasons. First, they allow reliable measurements of a number of gases that degrade when stored in stainless steel flasks, particularly at dry locations and when the delay between sampling and analysis is long. For example, reliable flask measurements of methyl bromide, bromoform, methyl iodide, carbonyl sulfide, and other gases are only possible at the South Pole from glass flasks. Secondly, glass flasks allow us to determine if results for many gases are independent of flask type (e.g., at CGO and SPO). At some sites, however, only glass flasks are used (PSA, SUM, WIS, and, initially, WLG). Finally, glass flasks allow sampling at new sites for much lower start-up costs than if stainless steel flasks were used. This has been an important factor in us being able to increase the number of sampling sites in our network has in recent years. The main downside of using glass flasks is that they prevent reliable measurements of specific compounds owing to contamination, probably related to the Teflon o-rings and the chemicals they came in contact with during manufacture. In the 1980s this contamination was observed for CFC-113; since then we have observed enhanced levels of HCFC-141b, and C
2
Cl
4
in glass flasks.
In mid-2006 measurements from LEAPS were stopped. Continuity of measurements was provided for three halons by the GCMS (M1) analysis of flasks. While two of the halons could be measured readily by the GCMS in its existing configuration, it was possible for H-1301 during 2006 and 2007 only by reanalyzing flasks with a short plug of ascarite in the sample stream (not the typical configuration). Ascarite removed CO
2
from the sample air stream and allowed quantitative analysis of more volatile gases free from the multiple matrix effects (in the transfer of condensed sample to the column, and in the mass spectrometer.