Siloxanes are commonly found in both biogas and landfill gas. This family of organic compounds have a negative impact on machinery causing wear on internal parts with increased operating costs as a result.
This analysis is performed using procedures adapted from EPA Method TO-17, ISO Method 16017, and NIOSH Method 2549.
Air samples are collected into tedlar bag on-site and then, using a syringe, a 60ml aliquot is drawn through the TD tube (type SVI). Sampling kits and instructions are provided to the client.
|Typical sampling volumes
0.05 to 1L
|TD Tube||Volume = 0.05L for µg/m3
|RL Units||RL Units|
Octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5) are commonly reported from landfill gas samples. D4 and D5 are often observed in biogas, while trimethylsilanol is not as common.
The method permits sample collection with Thermal desorption tubes and Tedlar bags. The sample is collected into a tedlar bag and on-site an aliquot is drawn onto a TD tube with a syringe.
Some of the siloxane compounds are soluble in water (most notably Trimethylsilanol and D3). Therefore, high humidity (>90%) may hinder the overall siloxane recovery. Condensation inside the tubes may also reduce the performance of the sorbent resin, however the SVI tubes utilized by ALS for this perform well in the presence of significant moisture.
SVI tubes perform well down to -15 °C/ 5 °F
Holding time for samples in Tedlar for siloxanes testing is 72hrs, however collection on-site onto TD tube stabilizes the samples and extends the hold time to 14 days. Thermal desorption tubes are cost effective, and easy to ship.
TD tubes are stable for up to 14 days after sampling and may be stored at room temperature prior to analysis. Tedlar bags may be stored for 72 hours prior to analysis.
There is no specific target analyte list in ASTM D8230. The list reported varies among laboratories from 5 to 22 siloxane compounds.
ALS reports the following silxoanes:
(see table above)
ALS reports results in: