GC is a high-resolution method for separating volatile and semi-volatile compounds. The gas mixtures are separated based on the differences in component distribution between a stationary phase (e.g. inner coating of a capillary) and a mobile phase (purge gas, e.g. helium). Since this gas separation in the GC column takes a certain amount of time – the duration of which depends upon sample characteristics, column flow rate, column length, and stationary and mobile phase – it is not possible to couple directly into the GC with a continuous online sample gas flow.