什么是卫兵栏目以及他们在HPLC分析中提供的好处？

The efficient operation ofHPLC systemis dependent on freedom of mobile phase and sample from chemical impurities or solid suspensions.Precautions in handling and use of HPLC mobile phasediscusses measures that should be adopted during preparation and use of mobile phase.Importance of sample filtrationdiscusses benefits of clean sample injections.

HPLC column is a critical component of the HPLC system which requirescareful handlingand protection. It is expensive to keep replacing columns frequently so your objective should be to maximize the useful life of the column so that every time you get the desired accuracy and consistency of results.

的色谱行为theHPLCcolumn begins to decline over use due to gradual accumulation of impurities and suspensions. Particles larger than 2μm present in mobile phase or sample start to deposit on the inlet frit of the column thereby disturbing uniformity of flow. Smaller particles result in increased backpressure so they begin to block the flow path in the stationary phase.

Nature of contaminants

• Highly retained compounds such as fatty acids in reverse phase separations
• Irreversibly retained compounds like residual proteins which were not removed completely at time of sample extraction.生物液中蛋白质的脱淡化化before HPLC analysis is strongly recommended.
• Particulate impurities can result from non filtration of samples, particulates released by wear of system components such as seals in the pump or injector.
• 用柱内的残留缓冲液干燥产生的结晶沉积物。使用或缓冲溶液后用HPLC级水洗涤柱防止这种盐沉积物形成。

什么是守卫栏？

A guard column is a protective column or cartridge installed between the injector and the analytical column. It serves to remove the impurities and suspended solids from reaching the analytical column. Typically it has a length of about 2 cm and internal diameter of 4.6 mm. Guard columns are packed with pelicullar particles of around 40 μm size to offer negligible pressure drop.

Desirable features of guard columns

• Guard column should have preferably the same packing as the analytical column to eliminate separation complications
• Internal ID of guard column should be comparable to analytical column to minimize back-pressure. Shorter guard column length is preferable but it should be long enough to prevent strongly retained compounds from reaching the main column
• 面向喷射器的玻璃料应通过去除约2毫米材料并用新鲜材料填充来除去清洁
• 与可再填充的防护柱相比，使用一次性墨盒式防护柱是方便且经济的使用。

需要定期改变防护栏，但通过观察色谱行为的变化，如背压，峰值扩大的增加，峰值的变化，中间变化是必要的。然而，可以基于样品的化学成分，存在高度保留或不可逆的保留组分，注射体积或注射次数来确定变化的频率。

Please share your experiences on use of guard columns and do leave your comments.