A precolumn filter placed between the sample injection valve and the HPLC column protects the column from particles originating in the sample and from pump and valve seal wear.
Precolumn filters are typically placed between the injection valve and the column, and because sample is present in the flow path it is important to keep volumes low. Therefore, precolumn filters typically feature smaller thru-holes, smaller frit diameters, and lower overall internal volumes than do inline filters.
Why use a precolumn filter when there is a frit at the head of the column itself? Changing the column frit is extremely difficult to do without disturbing the column packing. A precolumn filter provides relatively inexpensive insurance against column damage, and changing its frit is easy.
Upchurch Scientific® precolumn filters are available in two 'families' - MicroFilters and traditional analytical scale.
Upchurch Scientific® precolumn MicroFilters connect directly into microbore or analytical columns. Total theoretical void volume is only 0.5 µl, which includes frit volume. The PEEK™ tubing used has a 0.005" (125 µm) ID that virtually eliminates any mixing of the sample with the mobile phase. Two MicroFilters versions are available: one that connects ¹/₁₆ Ext.Ø tubing to columns with 10–32 threads, and another that uses MicroTight® tubing sleeves for 70 to 520 µm Ext.Ø capillary tubing. Choose from versions that come complete with 0.5 µm porosity stainless steel or PEEK™ frits. A 2 µm stainless steel replacement frit (53501-346) is also available.
Traditional precolumn filters are designed for standard HPLC or UHPLC and are either placed inline along the fluid pathway between the injection valve and the column (HPLC versions) or are connected directly into the 10 to 32 coned port of your column or other piece of hardware (VHP versions for UHPLC). The standard HPLC line includes both stainless steel and biocompatible flow path versions. The direct-connect VHP Precolumn Filters incorporate an adjustable-length tube and accommodate almost any port depth to virtually eliminate dead volume.