Types of Liners and their Selection

A GC inlet liner plays an important role in transfer of the injected sample into the GC column. It provides an inert surface for conversion of the injected liquid sample to vapour and transfer to the column without any change in its characteristics.

李ners are available in different design configurations with or without deactivation and with optional packings. The choice of a liner is based on the sample type and type of injection technique adopted. The topic covers the suitability of different liners for different injection techniques.

Selection Based on Type of Injection

分裂注射

当分析物浓度高并且不需要低水平检测时，采用分裂注射。这样的注射以较高的流速进行，并通过分裂通风孔导致样品的一部分进行。样品蒸气在衬里上的时间更少。这样的衬里需要快速汽化。选择玻璃羊毛填充的衬里，因为它们提供了增加的表面积，并且在注射过程中擦除了注射针，以提高重复性。分析活性样品（例如农药）时，应优选打开包装的衬里。在这种情况下，玻璃羊毛堆积可以导致o形成故障产品。

无分裂的注射

Splitless injections are useful for trace level analysis. Preferably use a deactivated liner and use of deactivated glass wool will improve analytical performance. The wool helps concentrate the sample from where it can vaporize. Further it prolongs useful life of a column by preventing nonvolatile sample components from reaching the column. The position of glass wool can assist in improvement of sample transfer. Injection reproducibility is improved by transfer of the injected sample into the glass wool as the needle tip is wiped every time on removal. Displacement of glass wool plug can be restricted by positioning it between baffles inside the liner.

清洁后可以重复使用打开的衬里，但清洁过程可以导致表面活动增加并导致性能不佳。

Direct Injection

Direct injection is used when trace level determinations are required and then there is a possibility of degradation of active sample components. The sample is injected directly into a hot inlet to allow the entire sample to be vaporized into the GC column. Such liners usually come with a press-fit connection at the bottom which fits and makes leak free contact with the column. Such liners have a hole drilled either at bottom or top. Semi-volatile compounds are analyzed with bottom hole liners and for aqueous solvent samples top hole liners give improved results.

Programmable Temperature Vaporization (PTV) Injections

将样品注入冷入口，然后进行加热程序，从而导致组件蒸发以引入色谱柱。PTV衬里的内径较小，并带有挡板，以将样品的湍流和快速传热引入柱。

In summary the choice of a liner is dependent on the injection technique selected. Liners with deactivated surfaces and deactivated glass wool packing can be used safely for most applications involving active components. However, for very sensitive compounds use liners without glass wool packings. For gaseous samples where there is no need for vaporization the liner is required to efficiently transfer the sample to the column. A narrow bore liner of 1.0 mm id is recommended for introduction of the sample as a sharp band into the column.