Chromatography Forum

Hi Everyone,

My lab is looking to purchase a few thermal desorption tube systems and I don't have any prior experience working with these types of systems. I'm looking to see if anyone has any experience with tube desorbers and could provide me with a recommendation on systems they like.

I'm currently looking into tube desorbers from Markes and CDS Analytical.

I have a Markes TD-100xr. I like it very much. Mostly I do SBSE work with it but I have done some work with the sorbent sample tubes. My Markes system is connected to an Agilent 7890/5977 system. I have their dean's switch in there so that I do heart-cutting (nonpolar first column to FID, polar second column - into the MS).

I've been using it for 1.5 years now and the only trouble I had with it was once it started leaking at the o-ring which seals the cold trap (volatiles are desorbed from the sample tube and recollected on the cold trap). I simply reseat that cold trap and it hasn't given me any trouble since. This leak manifested itself in 100% "high pressure test" failures on my sample tubes. The system does a high pressure test on your sample tubes to make sure they're not leaking. If it leaks, it doesn't ruin your sample. Pretty cool!

I can't comment on the other system. Perhaps someone else can give you some insight there.

Hi Everyone,

My lab is looking to purchase a few thermal desorption tube systems and I don't have any prior experience working with these types of systems. I'm looking to see if anyone has any experience with tube desorbers and could provide me with a recommendation on systems they like.

I'm currently looking into tube desorbers from Markes and CDS Analytical.

For thermal desorption you may want to consider a couple of additional vendors.
CDS Analytical - 9350 and their new robotic sampler
Perkin Elmer - Turbomatrix
Markes - has a couple options on the Unity line
Gerstel - TDU as part of their MPS rail system

The above list is in order of relative cost. I am aware Shimadzu makes a system, but it may be a rebranded Dani, it depends if you are in EU or USA.

Try each one with the compound set you work with. Also look at from a workflow and consumables standpoint. How expensive are traps and tubes, can you repack them yourself, are you allowed to repack? Take a look at ease of maintainance, changing traps, o-ring, transfer lines. Gases, some options require liquid nitrogen.

I wouldn’t make a recommendation without more information from you. Contact vendors, get quotes, study flow diagrams, ask more questions here.

Hi Everyone,

My lab is looking to purchase a few thermal desorption tube systems and I don't have any prior experience working with these types of systems. I'm looking to see if anyone has any experience with tube desorbers and could provide me with a recommendation on systems they like.

I'm currently looking into tube desorbers from Markes and CDS Analytical.

For thermal desorption you may want to consider a couple of additional vendors.
CDS Analytical - 9350 and their new robotic sampler
Perkin Elmer - Turbomatrix
Markes - has a couple options on the Unity line
Gerstel - TDU as part of their MPS rail system

The above list is in order of relative cost. I am aware Shimadzu makes a system, but it may be a rebranded Dani, it depends if you are in EU or USA.

Try each one with the compound set you work with. Also look at from a workflow and consumables standpoint. How expensive are traps and tubes, can you repack them yourself, are you allowed to repack? Take a look at ease of maintainance, changing traps, o-ring, transfer lines. Gases, some options require liquid nitrogen.

I wouldn’t make a recommendation without more information from you. Contact vendors, get quotes, study flow diagrams, ask more questions here.

Thanks for your input. I do appreciate it and I was mainly looking to see if anyone had experience using these systems.

All sales people will vouch for their machines so I was just looking to see if anyone had any recommendations based on their usage of the equipment.

I've narrowed down my selection of thermal desorption systems to Markes and Gerstel. I know Markes is closely aligned with Agilent and their engineers can service Markes systems. But, does anyone know the reliability of Gerstel systems in general and if they are easy to maintain?

We had an old flat-tray Gerstel system. It was difficult to get it lined up. Because of that, we didn't get the full utility out of that old system. It was retired with almost no use.

My best experience is with the Markes TD-100xr. I like it. I get good sensitivity - easily as good as SPME (my other method of choice for volatiles analysis). I still use a lot of SPME because you don't have to do anything special for water handling. Lots of my samples are substantially aqueous or a lot of water is generated during the heating of the sample. The heartcutting feature on my system helps me attack difficult separations because I can get some 2D separation capability. I like the Markes system because I don't have to have a tank of liquid nitrogen (or CO2) sitting around to make it operate. The cold trap is peltier cooled. I've had good luck with both stir bars and solid-sorbent tubes for sampling.

What are your samples?

The samples that I'm collecting are gas samples that are captured on thermal desorption tubes. I'm looking at hydrocarbon levels coming from the inert gas streams coming from the outlet of systems that we make.

I just had someone from Markes and Gerstel stop by to tell me about their systems. The Markes salesperson seemed really helpful and informative. Gerstel systems seem to rely way too much on their rail system. However their TDU trap seems to have less moving parts which to me seemed like a positive. In addition, the system uses LN2 which is great for capturing condensable compounds.

I get the feeling that Markes is a better vendor than Gerstel.

I can't comment on the folks from Gerstel but my friends at Markes have been very helpful to me in troubleshooting and also in helping me find method parameters. No charge. Very good email correspondence.

Gerstel uses the CTC rail for liquids and SPME, but adds in a thermal desorption unit. Installation is not too hard, alignment is easy. The older MPS systems had bungie cords that need replaced, the new robotic solved that problem. Mobile labs that have rails end up having to re-align a lot. If you want to do liquid, SPME, and thermal desorption on one GC with a single column, get the Gerstel. You will burn through liquid N2, but its the best way to run their focussing trap.

The Markes thermal desorbers have undergone a lot of improvement over the past 15 years. I have some of the older systems. I've been assured that all of their problems are solved. Find someone who has a newer system.

Get in touch with PerkinElmer. You will be surprised at their price compared to the Markes and Gerstel systems. Maintenance of the PE systems is pretty easy with everything accessible in the front.

CDS makes a nice hardened system for mobile lab use.

We have systems from all four vendors. I have my own preferences, some of which come from years of use, some based on shiny new toys.

What range of compounds are you looking at? On a C-series scale? Low end - C2, C5, C8? High end - C32, C40, C44? Some of the TDUs work better at low or high C-series ranges. You may need cryocooling for your GC.
Take samples to vendors or someone who has an instrument. Look at recoveries, carryover from trap desorb to trap desorb. For SVOCs and heavier, I expect less than 2%, anymore indicates inadequate desorb flow or a cold spot. I have seen as much as 15% with a vendor claiming zero carryover.

Thank you for letting me know about your thoughts on the Gerstel system. When looking at it , it seemed like a good system if I were doing many things other than thermal desorption. However, I'm looking at ppt levels of hydrocarbons; so the cryo focusing was my main draw to it.

With your older Markes systems, were they helpful with support to get your issues resolved?

I'll reach out to Perkin Elmer in regards to their systems.

For the CDS system, do you think it would be good for a high throughput lab? They are a bit slow to reach out so I haven't dealt with them much.

For the C Levels, we are honestly looking at a range of C3-to C30. Our customers really cares about compounds after C8 that are on the thermal desorption tubes.

If you had to run samples on a commercial level, what would you recommend?

just buy the perkin elmer turbomatrix 350. Its my recommendation for all you questions.