SGE has developed an inexpensive system for interfacing glass or vitreous silica capillary columns to mass spectrometers (MS). This interface allows the column exit to be maintained above atmospheric pressure, thus the column performance and retention indices are the same as those on an FID. The sample flow path to the MS is extremely inert vitreous silica or neutral borosilicate glass (GLT) with no dead volume and the unit can be heated isothermally up to 320 degrees C. Based on the open split system described by Henneberg et al*, the system is simple and easy to install. It consists of three basic components:
- Open Split Adaptor
- Deactivated Fused Silica Restrictor Tubing
- MS Connection
Open Split Adaptor
The main function of this stainless steel device is to insure the zone between the end of the capillary column and the inlet of the interface line is maintained slightly above atmospheric pressure. A low helium purge of approximately 0.5 ml/min. from the 1/16 inch line insures dead volume in the device is minimized thus eliminating tailing effects. For temperature programming we recommend the purge be controlled by a mass flow controller. By increasing the purge flow to a much higher flow rate, (100-150 ml/min) solvent dumping and heart cutting of selective peaks can be achieved thus protecting the sensitive ion source against sample overload. The 1/16 inch O.D. gas outlet line can carry flow to atmosphere or alternatively can be connected to a GC detector to monitor eluents. All connections are made with SGE graphitized Vespel® ferrules.
Flexible Fused Silica Interface Tubing
Each kit is supplied with two meters of deactivated flexible fused silica capillary tubing which functions as a fixed restrictor between the open split adaptor and the MS.
A heating device for the interface tubing is not supplied with these kits. If an interface oven is not built into the MS instrument, we suggest a simple heater can be constructed using copper tubing with a wrap-around tape heater, controlled with a thermocouple type temperature controller. Deactivated fused silica tubing can be ordered separately.
Kits are available which fit directly into HP5985 and HP5995 GC/MS instruments. For all other GC/MS systems a universal interface is offered which includes ¼ inch, 1/8 inch and 1/16 inch MS connectors. Operation of the open split interface and a detailed article on its installation into the HP5985 can be found in Vol. 1 of The Mass Spec Handbook of Service.
* Chromatography 1978, pages 111-130. Published by Elsevier Scientific Publishing Company.
|GC/MS Open Split Interface|
|062444||Item 2VSD-050. 0.05mm ID Deactivated Silica Tubing||$28.80|
|062445||Item 2VSD-060. 0.06mm ID Deactivated Silica Tubing||$28.80|
|062446||Item 5VSD-110. 0.110 ID Deactivated Silica Tubing||$28.80|
|* Standard lead-time for non-stock items is approximately two weeks depending on the item.|
|Ordering information. International (non-US) prices available through your local dealer.|
* 3-4 week delivery