8.6 Humidifying the make-up flow

• An increase in humidity is used to increase separation of analyte peaks in the DF matrices produced by the Lonestar.
• One way of doing this is to take the make-up flow from another source, for example an Owlstone Humidity Generator (OHG).
• Very important: As the make-up flow enters the At-Line Sampling Module after the particulate filter, it is very important that the air is clean (<0.1 ppm methane) and free of particulates.
• Another way of humidifying the make-up flow is to pass the flow through the headspace of a vessel containing deionised water. See Figure 23 for an illustration of this. The final humidity of the air flow will depend on several factors, including the air flow rate and the temperature of the water.

Humidifying make-up flow by passing it through water headspace