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Installation Instructions for the Model 961 GC Cryo-Trap on the HP 5890 Series GC


Site Preparation

Connecting Liquid Nitrogen

A low pressure (<50 psi) tank must be utilized to supply nitrogen in liquid phase to the remote liquid nitrogen valve. A minimum 1/4" o.d. stainless steel or copper line should supply the liquid nitrogen from the tank to the valve. The 1/4" copper line supplied with the Cryo-Trap should be used to carry the liquid nitrogen from the valve to the GC Cryo-Trap inside the GC oven. All of these lines and the liquid nitrogen valve should be insulated if possible. Foam pipe insulation or a similar material can be used to prevent water condensation and ice build-up. Installation of the lines will also greatly decrease the time required to cool the lines and valve when the LN2 valve is first opened.

Schematic of GC Cryo-Trap mounted inside GC Oven.

The GC-Cryo-Trap consists of three components; the Electronics Console, the Cryo-Trap Module and the remote LN2 valve. The Electronics Console is designed to sit on top of or in close proximity to the Gas Chromatograph (Fig. 2 and 3). The Cryo-Trap Module is designed to be mounted inside the GC oven just under the front injection port. A mounting bracket is clamped to the bottom of the injection port and the Cryo-Trap is then clamped to the mounting bracket. The only modification to the GC that is required is the removal of the GC injection port cover as explained below. The LN2 valve should be mounted as close as possible to the entrance of the LN2 line into the GC oven wall. You may wish to cut the 1/4" copper line if it is too long. No additional mounting screws or drilling of holes is required.

Figure # 6

Figure # 6 - Remove Protective covering over GC injection port inside GC oven.

Step 1

Begin by opening the GC oven door. The mounting bracket is to be mounted just under the injection port (Figure 6). Initial installation can best be accomplished with the GC column removed. However, installation can be accomplished with the column installed provided that extreme care is taken by the installer to avoid breaking the GC column. First, loosen the 2 screws (Figure 6) and remove the protective covering from beneath the injection port (Figure 7).

Figure # 7

Figure # 7 - Protective Cover removed from GC injection port.

Install the flat replacement protective cover supplied with the GC Cryo-Trap installation package (#900400) using the same two screws. (Figure 8)

Figure # 8

Figure # 8 - Install new flat protective cover on injection port.

Step 2

The Cryo-Trap mounting bracket is designed to clamp to the stem of the GC injection port fitting that attaches to the GC injection port (Figure 9) using the two hex head bolts.

Figure # 9

Figure # 9 - Installing mounting bracket to GC injection port.

Step 3

The Cryo-Trap horizontal positions are fixed, since the trap is aligned by the mounting bracket directly under the GC injection port. (Figure 9) To adjust the height of the Cryo-Trap, loosen the two knurled nuts on the Cryo-Trap mounting bracket. (Figure 10) The Cryo-Trap can then be positioned up and down within the Cryo-Trap mounting bracket. This will permit the easy installation and attachment of the capillary columns.

Figure # 10

Figure # 10 Adjusting height of GC Cryo-Trap in the mounting bracket

Step 4

Feed the Electrical lead up behind the Cryo-Trap module (Figure 11) and out through one of the exit ports in the GC oven. A convenient GC oven exit to use is the port for a second GC injection port. This second GC injection port exit is preferred due to its close proximity to the Cryo-Trap in the GC oven. Carefully move the insulation in this port to one side, or if preferred remove this plug of insulation for the easy passage of the electrical leads. Other exit ports such as spare detector ports could also be used.

Figure # 11

Figure # 11 - Feed electrical leads through GC oven wall.

Step 5

Next slide the 1/4" x 1.0 meter length of copper tubing (part #961200) through the same hole that the electrical lead exited from the GC oven (Figure 12). Attach the 1/4" nut from this cooling line to the top fitting of the Cryo-Trap module. Keep this copper line and electrical line as short as possible inside the GC oven and position so as not to interfere with the GC column. Use of the exhaust port is optional.

Figure # 12

Figure # 12 Attaching gas cooling line to GC Cryo-Trap

Step 6

Install the GC capillary column in the GC oven. Depending on whether the capillary column itself or a guard column is to be used for trapping in the cryo-trap, insert this capillary column inside the Cryo-Trap module from the bottom. If necessary loosen the Cryo-Trap clamp and slide the Cryo-Trap module upwards to allow more room for inserting the capillary column inside the Cryo-Trap module. If you have difficulty in finding the entrance hole at the bottom of the Cryo-Trap module, the Cryo-Trap module can be removed from the mounting clamp bracket and turned slightly sideways to better view the bottom of the Cryo-Trap module for insertion of the capillary tubing.

Figure # 13

Figure # 13 Attaching GC injection port fitting

Step 7

After the capillary column (or guard column) has been inserted through the Cryo-Trap module, attach the GC injection port fitting and appropriate column ferrule (Figure 13). The Cryo-Trap module can be lowered in the Cryo-Trap clamp to better facilitate the attachment of these fittings. It is also advisable to cut the end of the capillary off after the ferrule has been attached to avoid any possibility of ferrule contaminants from entering the column. Then slide the column up into the GC injection port the required distance and tighten the fitting and ferrule to hold the column in place.

Figure # 14

Figure # 14 Adjust gap between GC Cryo-Trap and GC injection port nut.

Step 8

When the capillary column has been attached, loosen the Cryo-Trap clamp and slide the Cryo-Trap module up to provide a gap of between 2 to 10 mm between the GC injection port capillary nut and the top of the Cryo-trap (Figure 14). This will minimize the dead volume between the injection port and the Cryo-Trap module and still maintain a thermal barrier between the injection port and the Cryo-Trap module. Tighten the Cryo-Trap clamp to hold the Cryo-Trap module in place.

Step 9

If a guard column was used, cut the end of the guard column to within 25 mm from the bottom end of the Cryo-Trap module and join this end to the capillary column using an appropriate fitting. When joining most microbore capillary columns to megabore guard columns, the capillary column will slide inside the guard column for 10 to 20 mm to minimize any possibility of active metal surfaces being exposed to the samples being analyzed.

Note: We prefer to use the SGE low dead volume unions for this connection.

Step 10

Tighten all fittings and attach the other end of the column to the detector or Mass Spectrometer.

Electronic Control Connections

Step 11

Attach the lead from the Cryo-Trap module to the connector labeled "Cryo-Trap" on the back of the Cryo-Trap Electronics console (Figure 15).

Figure 15

Figure # 15 - Back of GC Cryo-Trap Electronics Unit

Step 12

Connect the plug at the end of the LN2 valve control lead to the LN2 valve connector socket on the back of the Cryo Trap controller. (See Figure 15)

Figure 16

Figure # 16 - Installation of GC Cryo-Valve for Liquid Nitrogen

Step 13

Connect 1/4" copper tubing from your source of liquid LN2 to the 1/4" fitting on the inlet side of the electronic LN2 valve (see Figure 16). The 1/4" copper tubing (#961200) which was installed on the Cryo-Trap earlier is for connection to the outlet side of the LN2 valve. This copper tubing should be kept as short as possible, therefore we recommend that it be cut shorter if possible. Connect the line leading from the GC Cryo-Trap to the outlet end of the valve. The inlet and outlet fittings are clearly marked on the valve. All of these lines as well as the valve should be insulated if possible. Foam pipe insulation helps to prevent water condensation and ice build-up on the lines.

For instruction on the operation of the GC Cryo-Trap - see the Operating Instructions.