(Note: Do not use these needles with the AutoDesorb)
In the Short Path Thermal Desorption System, the needle serves as the transfer line for sample introduction into the Gas Chromatograph from the Glass Lined Thermal Desorption Tube containing the samples being analyzed. This short path for sample transmission is a key advantage of the Short Path Thermal Desorption System minimizing sample decomposition, eliminating sample contamination (memory effects) of the transfer lines, and providing for maximum delivery of samples into the Gas Chromatograph (maximum sensitivity). In any sample introduction system utilizing a needle to introduce samples into the GC injection port, needle selection is an important consideration. Selection of the correct needle type will depend upon the type of GC Septa used or if a septumless injector such as the JADE Injector is utilized. The following tables describe some of the variations in needles available from Scientific Instrument Services for the Short Path Thermal Desorption System. Side hole needles are recommended for most applications.
Selection of Needles for Thermal Dessorption
Needles for Desorption Tubes are available in a wide variety of sizes and shapes. Needles are permanently silver soldered to stainless steel caps to provide for a strong leak-free needle assembly. These needle assemblies screw onto the ends of the Desorption Tubes using one of the various types of seals available to provide a leak-tight connection between the needle assembly and the Desorption Tube. Depending on the application and on the type of injection system of the GC, a suitable length of needle will need to be utilized. Needle lengths between 25 mm and 60 mm are available. The shorter the needle, the longer the expected life of the needle. Longer needle lengths are more susceptible to needle bending on injection. However needle bending is minimal due to the autoinjecting system. Three styles of needles are available to suit the users needs, including a special needle for the Jade injection system.
The side hole needle is the recommended needle for use with the desorption system on GC's with septa. The side hole needles, although more expensive, minimize septa coring but still provide good penetration of septa. The 20¡ point needle is the standard needle for general gas chromatography with septum type injectors. It provides excellent septa penetration, however, it can be susceptible to septa coring, and it is therefore necessary to frequently inspect the needle for plugging. When using the Jade injection system it is necessary to use the Jade point needles. Other dome tip type needles will not work with this injector. The Jade needles have a precision angled dome end to smoothly pass through the injector. The optimum needle will vary with injection system, application and septa type and must be determined by the user. Some of the needles listed have smaller inside diameters, which will result in lower gas flow rates through the needle. This may prove to be a disadvantage when using systems requiring higher flows such as in capillary split modes of operation.
If the needle type required is not listed, other needle types and sizes are available on special order from Scientific Instrument Services.
*Jade Point needles are special order. Delivery 8 weeks.
| Desorption Tube Needle, UOM=EA | ||||||||
| Part No. | Tip Style | Needle Length (mm) | OD (mm) | ID (mm) | est wt. |
Quantity In Stock |
Price | Quantity to order |
|---|---|---|---|---|---|---|---|---|
| 781055 | Side Hole | 60 | 0.63 | 0.24 | 0.25 | 0(#) | --- | --- |
| 781052 | Side Hole | 50 | 0.63 | 0.24 | 0.25 | 0(#) | $28.00 | |
| 786035 | Side Hole | 35 | 0.63 | 0.24 | 0.25 | -5 | $33.00 | |
| 781054 | Side Hole | 25 | 0.63 | 0.24 | 0.25 | 0(#) | $28.00 | |
| 781021 | 20 deg point | 60 | 0.50 | 0.25 | 0.25 | 2 | $28.00 | |
| 781026 | 20 deg point | 50 | 0.50 | 0.25 | 0.25 | 0(#) | $28.00 | |
| 781027 | 20 deg point | 35 | 0.50 | 0.25 | 0.25 | 0(#) | $28.00 | |
| 781028 | 20 deg point | 25 | 0.50 | 0.25 | 0.25 | 3 | $28.00 | |
| 781022 | 20 deg point | 60 | 0.63 | 0.32 | 0.25 | 0(#) | $28.00 | |
| 781023 | 20 deg point | 50 | 0.63 | 0.32 | 0.25 | 0(#) | $28.00 | |
| 781025 | 20 deg point | 35 | 0.63 | 0.32 | 0.25 | 4 | $28.00 | |
| 781024 | 20 deg point | 25 | 0.63 | 0.32 | 0.25 | 0(#) | $28.00 | |
| 781041 | Jade point | 60 | 0.63 | 0.12 | 0.25 | 0(#) | $28.00 | |
| 781042 | Jade point | 50 | 0.63 | 0.12 | 0.25 | 0(#) | $28.00 | |
| 781043 | Jade point | 35 | 0.63 | 0.12 | 0.25 | 0(#) | $30.00 | |
| 781044 | Jade point | 25 | 0.63 | 0.12 | 0.25 | 0(#) | $28.00 | |
| (#) Standard lead-time for out-of-stock items is approximately two weeks. | ||||||||
Ordering information.
International (non-US) prices available through your
local dealer.
|
||||||||
Side hole needles are the preferred needles because they minimize
coring of the GC septum.
| SIS Catalog Cross Reference | |
|---|---|
| Page # | Part Numbers |
| C11 - AutoDesorb™ | 786035 |
| C14 - TD1/TD2/TD3/TD4/TD5 Needles and Seals | 781054, 786035 |
| C15 - AutoDesorb™ Needles, Seals & Connecting Tubes | 786035 |
 Yttria coated filament at start |
 Yttria coated filament after 16,000 cycles |
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