Fixed guards

Restek Rtx-IMS fused-silica open-tubular column (FSOT) with integral guard column, 30 m X 0.25-mm i.d. and 0.25-p.m film thickness Eppendorf fixed-volume pipets, 0.50-mL Eppendorf fixed-volume pipefs, 1.0-mL Eppendorf pipel lips, 1.0-mL Amber-glass boftles wifti Teflon-lined caps, 4-oz... 

For use with 25 cm x 4.6 mm analytical columns, guard columns and scavenger columns are often 4.6 mm internal diameter and 3-10 cm in length. They can be packed with microparticulate stationary phases or with porous layer beads. Porous layer beads are cheaper than microparticulates and are easier to pack, but they have lower capacities and will require changing more often. It is usually difficult to know how long a pre-column will last before it requires changing. In routine work, precolumns are usually repacked or replaced to a fixed schedule. 

ISO 14120, Safety of machinery — Guards — General requirements for the design and construction of fixed and movable guards... 

Every analysis performed on columns of this type (for example, carbohydrates, alcohols, organic acids, mixtures of these) can be improved with a column in the most suitable ionic form, even though solutions with compounds of differing types may impose the choice of a compromise. In analytical practice, however, it is not advisable to make an in-column conversion from one form to another, for the resin could shrink or even swell in relation to the type of cation linked. The effect of fixed-cation is made obvious when the compounds under analysis can coordinate with it, as in the case of carbohydrates. For example, the linkage of sugars with three adjacent hydroxyls may be more stable than those that have only two, with obvious effects in the resolution of the analytes. Finally, it is advisable to use a guard column to prolong the life of the... 

Remove fixing ring K23, transparent cap and rubber ring. Pull out tachometer and guide sleeve from the guard. Screw the tachometer out of the holder. The driving pin K20 can then be taken out in the same direction as the tachometer. 

Unicracking hydrodesulfurization (Unicracking/HDS) is a fixed-bed, catalytic process for hydrotreating of residua. In the process (Figure 9-30), the feedstock and hydrogen-rich recycle gas are preheated, mixed, and introduced into a guard... 

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