which headspace autosampler would you purchase?

[chemie1]

My company is looking at purchasing a headspace autosampler for our 7890 GC equipped with an FID. We have bids on over 6 brands. They all appear to be "great". We really need a unit that is robust- there will be multiple user with various degrees of technical ability. Is there a unit that anyone would recommend? I am leaning towards the TechMAR or Agilient unit. I just do not want to make a huge mistake.

Thanks for your help...

[Peter Apps]

A search of the forum archives will reveal some interesting information. As always the advice has to be to see demo models in action and think about the after sales technical service.

Peter

[krickos]

Hi

Software might be another issue to consider, for example our current version of Empower is not able to perform splitless injection with Agilent headspacesampler/GC.

[Schmitty]

Hi

Software might be another issue to consider, for example our current version of Empower is not able to perform splitless injection with Agilent headspacesampler/GC.

In regard to splitless headspace injection; we previously used a CTC CombiPAL with Agilent 5890s, without issue in splitless mode. When we upgraded to 7890s and moved the autosamplers over, we encountered issues with peak shape and sensitivity.

In order to achieve the same chromatography as previous, I had to modify the method to be split at a ratio of 0.1. This worked for a few months, but now the EPC in the 7890 for that inlet is shot. So, consider that if you aer using a 7890 or CTC CombiPAL.

We also have experience with the Teledyne Tekmar HT3, which also needs a split of at least 5 to work effectively.

[chromatographer1]

Much of your decision should be based on the limits of the performance required, the type of typical work for which you are using the headspace analyzer. (WARNING: SALES PITCH AHEAD Talk to an independent consultant first)

Valved based HS analyzers (Agilent and Techmar) are inherently afflicted with carryover peaks from the rotor materials and the metal transfer lines used in their design but are simple to service and to change loop sizes. If you wish to perform routine residual solvent pharmaceutical methods this design may serve your needs well.

If you are performing very low trace analyses with reactive and difficult analytes then a more inert but technically advanced analyzer like the Perkin Elmer design may be your preference.

See how difficult it is to replace transfer lines and sample loops and to clean your analyzers Nothing stays pristine forever. A dirty system is reactive and gives false carryover peaks as well as causing inaccurate measurements of trace analytes.

Fixed loop and timed injection designs both have advantages and disadvantages. Any system should have a mixer-shaker in the design. You should also have a choice of vial sizes, not just the 22mL but 12mL and even smaller vials in the range of 2-4mL which can be quite useful for accuracy and speed of final method parameters. Throughput is an important factor in the choice of an analyzer.

Many on the forum insist on using injectors which split the sample. This lowers the LOD and increases the variability of measurement. I am NOT a proponent of using a split sample or small bore capillary columns for headspace analysis. I used an inert direct injection system on Tekmar and Perkin Elmer systems (both valve and timed injection designs) and measured ppt levels of Benzene in water and percent levels of ethanol in aspirin using a GC with a FID system with minimum (nil) service issues for SEVERAL YEARS. I also measured triethylamine salts and ethyl acetate in peptides.

Whatever you purchase do not choose the standard system where bare metal contacts the sample. Nickel is NOT inert. You really should have glass or fused silica coated components where parts contact the sample.

Finally, quality of parts and service is always an important factor in choosing a HS analyzer. A unit sitting quietly on the bench doing nothing is never a good choice.

Finally, get demos and have the sales people perform actual analyses for trace polar and non-polar solvents in water and DMF solutions, using samples of 5mg to 1 gram and have them show limits of detection, and linearity and reproducibility of a wide range level (1ppm to 10% in the sample, not in the vial volume) in YOUR LAB.

Acetaldehyde and triethylamine are difficult analytes. Acetic acid and pyridine are real challenges. Rotor materials love to absorb esters like butyl acetate and other solvents.

It is your money and YOUR CHOICE.

best wishes,

Rodney George
consultant

[LindseyPyron]

Heads Up for a commercial!

Check out:

http://www.estanalytical.com/Products/F ... ov_HS9000/

The system does loo injection like the Agilent/Tekmar and can also be configure to do Tim e injection like the PE. All instruments in one. You can also do dynamic sweeping to a built in trap for better sensitivity if needed.

[Labgurl]

We have a 7890A, and an Agilent autosampler - works great! We haven't had any problems with it yet.

[che313]

check gerstel MPS
http://www.gerstel.com/en/mps-gc-ms-autosampler.htm

[greta]

Hi chemie1,
HTA's HT200H support all Agilent GC.
You should find confirmation on their website (http://www.hta-it.com)

Greta

[kahmark]

We recently installed a Gerstel MPS to our Agilent 7890, I like it due to the software flexibility. I sample GHG headspace. I can send you an image of our system if you like. It is very similar to the CombiPal but much more versatile due to the software enhancements. I am not a salesman but a lab researcher.

Kevin

[Charles A. Burger]

Fixed loop and timed injection designs both have advantages and disadvantages. Any system should have a mixer-shaker in the design. You should also have a choice of vial sizes, not just the 22mL but 12mL and even smaller vials in the range of 2-4mL which can be quite useful for accuracy and speed of final method parameters. Throughput is an important factor in the choice of an analyzer.

Rodney

Just wondering why you didn't mention the heated syringe type of headspace sampling? I'm now at a place that uses the Combipal setup and am trying to learn all that I can. I have worked with them in the past and have mixed feelings on their performance. I will admit, I didn't have a real good understanding on some of the more important factors involving headspace that I do now so hopefully this second round with this style goes better. I kind of have to since this is the ONLY technique available to me.

My guess is that the inertness level is better than the fixed loop, but not quite that of the pressure balanced technique. Also, I haven't confirmed this yet, but I may be able to use smaller injections than 10 ml which I believe you showed me in the past, can be quite a boon for sensitivity and flexibility.

Have you even had a chance to work with them? If so, please expand on this post with any pertinent info regarding heated syringe techinque.

Thanks

Charlie

[chromatographer1]

Charles,

You wrote:

" My guess is that the inertness level is better than the fixed loop, but not quite that of the pressure balanced technique. "

Your guess is good for the base hardware, but using the deactivated metal components that Tekmar provided me as a Beta tester back in the 1990s, my answer is PE, then Tekmar-Varian-Agilent fixed loop, then Combipal syringe.

My Mantra is :

I like inertness. Bare metal does not give inertness. I stay away from bare metal, especially if the sample has residence time in contact with bare metal (sample loops, syringes, etc)

I have worked with all of them.

For general purpose work they are all fine.

For research or difficult matrices or analytes, I like inertness.

Life is easier and better when nothing sticks to you, especially trouble.

Charles, write me for a private communication if you wish. See the line above why.

best wishes,

Rod

[Charles A. Burger]

how do I get a hold of you besides this site?

email: cseager@flemingpharma.com