Installation of the Short Path Thermal Desorption System - TD5

SITE PREPARATION

Space Requirements

The Short Path Thermal Desorption System is a compact, self contained injection system and desorption system that requires a minimum amount of space. The system is designed only for top injecting GC systems. The Thermal Desorption Unit sits directly over the injection port of the Gas Chromatograph. The base of the Thermal Desorption Unit is only 5.5 inches wide x 6.5 inches deep and the overall height is 22 inches.

The Electronics Control System is 7 inches wide x 14.5 inches deep x 11 inches high, and normally can sit on top of the GC oven cabinet providing it does not interfere with the operation of the GC. Alternatively, the Electronics console can be placed on the lab bench next to the GC or on any other suitable shelf or supporting medium within 4 feet of the GC injection port.

Fig.2.1 S.P.T.D. mounted on Varian 3400 GC

Line Voltage & Current

The Short Path Thermal Desorption System requires a single 115 volt, 10 amp, 60 Hz, grounded outlet. The system is fuse protected with a main power fuse and a second fuse for the cartridge heater circuit. In no case should a fuse larger than the size recommended in this manual be used.

Power requirements are 115 Volts +/- 10% AC and 10 amp max.

Gas Considerations

Desorbing Gas

Standard GC carrier gas is utilized as the desorbing gas for the Short Path Thermal Desorption System. High purity gases such as Nitrogen or Helium are recommended. The carrier gas should have a purity of at least 99.995% and must be delivered at 40-60 psi and 100cc/min maximum (0.04CFM).

The same carrier gas used for the capillary or packed column carrier gas should be used as the desorbing gas in the Short Path Thermal Desorption System to avoid mixing gases in the GC injection port; which could cause an unstable baseline, especially with FID detectors. Due to the high temperatures and rapid heating of the components in the desorption system, the use of hydrogen could create an explosive condition

CAUTION - DO NOT USE HYDROGEN GAS IN THE DESORPTION SYSTEM

NOTE: The carrier gas for the desorption system can easily be plumbed in by adding a cross or tee into the carrier gas line before it enters the gas chromatograph. The instructions below describe how to do this.

1. The installation of a cross or tee in the carrier gas line requires a tubing cutter, a 7/16 inch wrench and a Swagelok brass cross (B-200-4) or brass tee (B-200-3).

2. Turn off the carrier gas at its source.

Installation of Cross in Varian 3400 GC Carrier Gas Line

1. Figure 2.2 shows the standard gas hookup on a Varian 3400 GC.

2. Remove the 1/8 inch Swagelok tee and replace it with a 1/8 inch Swagelok cross. See Figure 2.3.

3. Use the top fitting to hookup the carrier gas line to the SPTD unit.

4. Be sure the tubing is completely seated in the fitting and tighten 3/4 turns past finger tight.

Fig. 2.2 Standard carrier gas hookup on Varian 3400 GC.

Fig. 2.3 Cross installed allowing carrier gas hookup to S.P.T.D.

Installation of tee in Agilent 5890 GC Carrier Gas Line

1. Figure 2.4 shows the standard carrier gas hookup on the Agilent 5890 GC.

2. Using the tubing cutter cut the 1/8 inch tubing about 2 inches from the back of the GC.

3. Check that the ends of the tubing that you just cut are clean, open and burr free.

4. Install the tee as shown in Figure 2.5. Be sure the tubing is completely seated in the Swagelok fitting and tighten finger tight. Tighten 3/4 turns further with the small wrench.

5. Use the side arm of the tee to hookup the carrier gas line to the SPTD unit.

Fig. 2.4 Standard gas hookup for Agilent 5890 GC.

Fig. 2.5 Tee installed allowing carrier gas hookup to S.P.T.D.

Compressed Air for Solenoids

A supply of clean compressed air or nitrogen is required. Compressed Air from Laboratory supply or cylinder at 40 psi, 100 cc/min maximum (0.04 cfm) is required. The fitting required for installation of the S.P.T.D. system is a 1/8 inch Swagelok fitting.

Cryo-Cooling

Cryo cooling capabilities using liquid Nitrogen or Carbon Dioxide are recommended for the GC oven or alternatively using the GC Cryo-Trap accessory. Normally samples are desorbed from the desorption tube and trapped on the front of the GC column. In some cases these volatiles can be trapped on thick film megabore columns such as the SGE BPX-624 column. However for microbore capillary columns and thin film columns it is preferable to cool the column below 0 degrees C in order to trap the volatiles. Cryo cooling is available on most gas chromatographs. Usually this accessory is ordered when the GC is first purchased, however most gas chromatographs can be upgraded to include cryo-cooling. For example, the Agilent 5890, 6890 or 7890 GC can be easily retrofitted with cryo cooling. The kit (available from SIS) costs less than $500.00 and requires about 20 minutes to install.

However for optimum results and minimum use of cooling gas, use the GC Cryo-Trap which can be purchased as an accessory for the SPTD System. The GC Cryo-Trap can be controlled via the SPTD electronics to regulate both cooling and heating temperatures as well as the switching between the two states.

Installation

Instructions follow for installation of the Short Path Thermal Desorption System (S.P.T.D.) on various gas chromatographs. The following sections are included:

Installation of the S.P.T.D. System on the Varian 3400

Installation of the S.P.T.D. System on the Agilent 5890

Installation of the S.P.T.D. System on other GC's

Careful adherence to these installation instructions should allow the user to install the S.P.T.D. system on either the Varian 3400 or Agilent 5890 gas chromatographs. Be certain that you read through the instructions completely and acquire all the tools required before proceeding. The section on site preparation found in this manual should also be read through completely to be sure that you are ready for installation.

For further help in installation call

S.I.S. customer support at
contact us.

The entire S.P.T.D. system can be installed by the end user. However, Scientific Instrument Services also provides installation by S.I.S. qualified staff. This includes installation of the Short Path Thermal Desorption on your GC or GC/MS system and training to get you up and running with your new system. Price includes all travel and lodging and expenses for 1.5 days at your location. Please call S.I.S. for more details.