Guard column and Pre-column inline filter are commonly used in LC experiments. But a lot of users are confused about the two products as they look similar. How to distinguish? What’s the difference? Follow us and you will get answers. 

The difference between Guard column and Pre-column Inline Filter

Both are connected in front of the column and can prevent solid particles from blocking the frit of the column.

However, there is a difference between the two. There is a frit inside the in-line filter with a certain pore size, which can only filter out some impurities larger than the pore. During cleaning, remove the frit, and ultrasonic it with water and methanol for 10min respectively, then it can be normally used.

Guard column cartridge is placed in the guard column holder and most of the cartridges can be replaced as needed. There is packing material inside the cartridge and same packing material with analytical column is recommended. Guard column can not only filter solid impurities, but also adsorb some strong polarity, strong acid or strong alkaline substances.

How to choose guard column?

How to choose the guard column scientifically without affecting the separation? First of all,  choose the guard column cartridge which has the same packing material with analytical column as we talked above. A 1cm long guard column provides adequate protection for most of the analysis. The longer the guard column cartridge is, the more packing material it contains, the more protective it will be, but the retention time of samples will increase correspondingly. Therefore, the principle of selecting the guard column is as follows: Under the premise of satisfying the requirements of separation analysis, choose the shorter guard column as far as possible, and choose the packing material with smaller retention to the samples as far as possible.

Classification of guard columns and in-line filters

At present, there are two main types of guard column and inline filter in the market: direct connection type and independent type.

The direct-connected type can be installed directly to the analytical column without additional pipelines or joints, which is much easier to use and its dead volume outside the column is smaller. While the independent type need joints and pipelines to connect to analytical column. Users can also choose the proper length of guard column and packing material according to different samples.

In addition, when selecting guard columns and in-line filters, we need to pay attention to whether the cartridge or frit can be replaced on this holder. Replaceable guard column and in-line filter holders can save costs.

Welch has a rich line of online filters and protection columns

If you have any problem or require further information, please contact

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