ASTM D-1946 and ASTM D-1945 Permanent Gases and Hydrocarbons
ASTM D-1946 and ASTM D-1945 are methods for measuring permanent gases in refinery samples using gas chromatography (GC) and a thermal conductivity detector (TCD). The TCD is used for measuring percentage levels of compounds so the method can be use to measure nitrogen, oxygen, methane, carbon dioxide, and carbon monoxide in ambient air and gas samples in the range of 0.05 to 100%. The EPA source test method is called EPA 3C. The method also covers measuring light hydrocarbons. The method also can be used with a combination of TCD and flame ionization detection (FID). Copies of the methods are available only on the ASTM website.
Word about Method Detection Limits (MDL)
Defining Detection Limits
Detection Limits are used to specify the lowest concentration of a compound that can be measured reliably by the analytical method. There are several definitions for the detection limits used by laboratories so it is important to understand the differences, so that the objectives of your project are met. On this web site, the term detection limit is used as a general term to collectively describe the more specific terms such as the Method Detection Limit (MDL), Lower Quantitation Limit (LQL), Reporting Limit (RL), and Method Reporting Limit (MRL), and Practical Quantitation Limit (PQL).