RSK 175 Testing for Methane, Ethane and Ethylene
Butane by RSK-175 is now also available!!
Teklab is an environmental testing laboratory that provides specialty analysis such as Method RSK 175 for dissolved gases in groundwater (or other aqueous) samples. Natural Attenuation Parameters such as Dissolved Methane, Ethane, Ethylene and Butane are measured in groundwater to monitor the effectiveness of remediation activities. As such, these dissolved gases are frequently generated from the degradation of more complex organics compounds during the remediation process. Please refer to the list of the permanent gases that we can test for.
The measurement of dissolved gases such as Methane, Ethane, and Ethylene in ground water is important in determining whether intrinsic bioremediation is occurring in a fuel or solvent-contaminated aquifer. A simple procedure is described for the collection and subsequent analysis of ground water samples for these analytes. A helium headspace is generated above a water-filled bottle. Gases that are dissolved in the water partition between the gas and liquid phases and equilibrate rapidly. An aliquot of this headspace is analyzed by gas chromatography to determine the gases concentration in this phase. The concentration of the gas dissolved in the water can then be calculated based on its partitioning properties, as indicated by its Henry’s Law constant.
Ethylene (C2H4) is a key chemical for producing a huge range of chemicals, polymers and plastics. Much of the world’s C2H4 demand is met via the Naphtha cracking of crude oil process. According to the Gulf Petrochemicals Association, around, 183 million tons of ethylene was produced worldwide in 2019. The CO2 emission cost of the process has been estimated at up to 2kg per kilogram of ethylene produced. The basic principle then is to covert methane into a methyl radical by removing a hydrogen atom through oxidation, and allowing the methyl radical to combine to form ethane, or preferably directly to ethylene by working in a high temperature environment.
Our RSK 175 procedure was developed from the journal article “Analysis of Dissolved Methane, Ethane and Ethylene in Ground Water by Standard Gas Chromatographic Technique” published in the Journal of Chromatographic Science, volume 36 in May 1998, and the RSKSOP-175 SOP that was prepared for the use of the Ground Water Ecosystems Restoration Division of the USEPA.
A summary of the procedure follows:
Aqueous samples are collected in 40 ml VOA vials. A 4.0 ml headspace is created in the vial. The vial is then shaken then equilibrium is established between the water and the headspace. A known amount of the headspace is injected onto a GC capillary column where the gaseous target analytes are separated then detected by a flame ionization detector. The concentration of the dissolved gas in the original sample can then be determined by using the Henry’s law constant (H) for the target analyte, the concentration of the gas in the headspace, the bottle volume, the sample temperature and the amount of headspace injected.
We realize that there are a lot of unique organic compounds in existence and local regulatory agencies may require testing for compounds that are not on the standard EPA or SW846 lists. When those situations arise, we can (and do) perform validation studies to see if your particular compound can be extracted and analyzed using those reference methods and thus meet NELAP accreditation standards.
We recommend that you contact a NELAP accredited environmental testing laboratory even if your organic compound of concern is not “routinely” analyzed or in an EPA approved testing method.
