Column Installation and Care

Column. The capillary column must be correctly installed into the inlet, a procedure that is inlet and instrument dependant. In general, the column end is placed a specified distance into the inlet, beyond a fitting at the bottom end of the inlet. Each instrument vendor provides specific instructions on column installation that should be followed carefully. It is especially important to ensure that the seal between the inlet and column is leak-free and not contaminated. 

Stop the flow rate, install one GPC 100-A column in the instrument and return the flow rate to 1.0 mL/min. (Read the column use instructions carefully.) ... 

The discharge side components are elbow, pipe and spool. It is very important to maintain the two sides, namely column side and discharge side pipes, parallel. Care should be taken during installation of the pump at the site to ensure that the weight of delivery side piping is mounted independently of the pump so that it does not induce stress on the bottom bearings of the pump. 

The price of a column ( 200- 800) may be viewed as relatively small compared to the initial, the routine, and preventive-maintenance costs of the instrument. In fact, a laboratory may find that the cost of a set of air and hydrogen gas cylinders of research grade purity for FID operation is far greater than the price of a single conventional capillary column Consequently, the column should be carefully selected for an application, handled with care following the suggestions of its manufacturer, and installed as recommended in the user s instrument manual to derive maximum performance from a gas chromatographic system. 

Making the proper connections, especially in the installation of a capillary column, is critical to the good practice of gas chromatography and to avoiding problems. The two most important considerations are that the capillary column be properly cut and that the column end be inserted the correct distance into the inlet. Proper column-cutting techniques are reviewed in the literature provided by the column manufacturers, and the inlet manufacturer provides the proper installation procedure. Note that these procedures may vary from manufacturer to manufacturer, so they should be studied carefully prior to installing a column. 

Install the column in the chromatographic oven and connect one column end to the sample inlet system. Turn on the source of carrier gas and set the flow controller (or pressure regulator) to the flow rate to be used in the analyas. Increase the column temperature to the maximum value to be used in the analysis and maintain this temperature for 30 min. Cool the column temperature to room temperature and connect the remaining column end to the detector. Care must be taken that the column terminates as close as possible to the tip of the FID jet. The temperature of the column between the column oven and the detector jet must be maintained above the maximum column temperature. 

The plastic plates and terminals are fitted into cast housings inside concrete columns or in built-up areas, in cable junction boxes installed at walls. Belowground test points should be installed in built-up areas only in exceptional circumstances. In this case watertight, flush-mounted test stations are installed under a street-level covering and can be kept dry only by the most careful construction. 

Another approach is to fabricate and install a precisely defined packing structure, which is carefully placed to fill the column. An example of a structured packing is shown in Fig. 8. Both types of packing are most commonly made from stainless steel. The surface area per unit volume is a key variable. Large surface area packings have lower efficiencies, higher capacities, lower pressure drops, and lower costs than small surface area packings. 

LEAKAGE AND WEEP HOLES. To ensure a minimum of liquid leakage from one tray to another, bubble-cap risers should be fitted firmly or sealed into the trays, and an effective seal is necessary around the tray supports. In large columns, the trays are often made in sections for ease of installation. Each of these sections must be installed carefully to minimize leakage. 

The elements of structured pecking are installed in layers in the column, with care being taken that the edjoining elements of adjacent layers are oriented such that the liquid flow direction is reversed and that gas is redistributed, For the simple pilot plant element shown in Fig. 5.8-4, edjncenl layers are usually totaled by 90°. 

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