Syringe injection is the most common and arguably the most reproducible method of headspace sampling. It is illustrated in the figure below.

The syringe is heated and agitated in an oven for a pre-defined period of time (step 1). The heated syringe then removes an aliquot of the headspace, (step 2) and injects it directly into the GC (step 3).

• Syringe Injection
• Balanced Pressure
• Pressurised Loop

Each of these will be looked at in turn in the following pages.

Step 1 Sample reaches equilibrium	Step 2 Sample is extracted from the headspace	Step 3 Sample is injected

The syringe must be heated above the temperature of the oven to avoid the risk of condensation and hence carry-over from one sample to the next. After injection, the syringe is flushed with nitrogen or other inert gas.

Advantages of a Syringe Injection System

There are several advantages of this type of system:

• Very high level of reproducibility
• Low carry-over
• Fast transfer of sample to GC
• Precise control of sample syringe for sample size and injection speed
• Easy to clean syringe
• GC injection port is always free for manual samples

Many syringe autosamplers can be retrofitted onto existing GC systems. The Manual Headspace Sampler is GC-independent and is a simple syringe injectiion system.