admin
Admin
| Posts: 138 |  |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:30
Is it possible to analyse resins by static headspace gas chromatography? If the answer is yes, at what temperature should the vials be heated before analysis?
|
|
|
reply | quote |
admin
Admin
| Posts: 138 | |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:30
I developed a method for evaluating differences in volatile components in hot melt glue resins by HS/GC many years ago. I was using a Genesis HS and a Varian GC with an FID. I do not remember the column. I developed the method a long time ago for the company where I was employed at that time. What type of HS instrument are you using? Is injection automated from the vial through a heated transfer line into the GC injector or is it transfered with an external syringe that has to travel through the air between the vial and the injector? This information will determine the parameters required for both HS and GC injection parameters.
|
|
|
reply | quote |
admin
Admin
| Posts: 138 | |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:31
I can use both manual injection or automated through a heated transfer line. The HS and the GC are both Perkin Elmer. The column is 5%diphenil-PDMS and the detector is a FID. I also have a 100% PDMS column.
I'm working at a printing ink company. We produce inks wich have resins. I already have a method for determining the nature and the amount of solvents present in the ink's composition. I'm now trying to identify and quantitate more of the ink's components, like resins. I'd like to have a data base of each resin's "finger print" in order to identify wich resins are present in each ink I analyse and in what amount.
It'd be very helpful if you could remember some of the parameters required.
|
|
|
reply | quote |
admin
Admin
| Posts: 138 | |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:32
The solvents should come off at the boiling point of water and could be handled under static pressure with syringe injections or via transfer line.
To get higher melting point components into a volatile state requires higher temperatures. Many years ago I developed a method for comparing volatiles in hot melt glue resins. We had a problem between 2 batches of supposedly the same material. Samples of different cartons from one batch all produced similar chromatograms when examined by HS/GC. Samples from the other batch produced different chromatograms from the first batch but were similar to each other. The supplier took back the poorly performing batch, credited our company and paid for our lost production after they saw the chromatograms.
I used nitrogen to pressurize the vial rather than static head pressure. This gives a better transfer of material to the sample loop and helps prevent oxidation. I held the sample loop and tranfer line at the maximium, 200C. I heated the vials to a temperature 20C below the maximum of the transfer line, 180C. This prevented depositing in the sample loop or transfer line. The injector was 30C above the temperature of the transfer line, 230C, to make sure all material was deposited on the column. The column starting temperature was 25C above room temperature, 50C. This focused all analytes on the head of the column. It really worked well for my samples. Check the MSDS of the inks and resins to make sure you do not use temperatures that might break down components. An FID will give a nice finger print chromatogram. An MS detector would allow identification of the peaks by providing finger prints of the components comprising the peaks. An MS library might even name the analytes in the peaks. Good luck with your work.
|
|
|
reply | quote |
admin
Admin
| Posts: 138 | |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:32
Inês,
If you are wanting to characterise the resins, could I suggest that Pyrolysis GC is probably a better method since I guess the resins in the inks are not volatile and therefore would not be in the headspace. PyGC is a good fingerprinting tool and is relatively cheap. When coupled to a MS the cost increases but the information you acheive is much better.
Alternatively, FTIR would provide information on the type of resin present and in many cases can be quantified.
|
|
|
reply | quote |
admin
Admin
| Posts: 138 | |
|
Analysing Resins by Static Headspace GC - 2005/11/28 18:33
Ian is correct on all counts. When I saw HS, I assumed you were only interested in the resin's volatile components. That was my interest in the hot melt glue resin. If the volatile components were not the same batch to batch, the glue would not harden quickly enough to bond the case flaps. I assumed you were interested in the ink resin's volatile components for drying effect. If that is the case, a double run might be the best way to go. The first, at low temperature, 100C, with static head pressure. The second vial I would put in a vaccuum oven at 60C before applying the cap. I would then place it in the HS unit at perhaps 200C and sample with the assistance of nitrogen pressurization of the vial. If you are interested in the resins rather than the volatile components, HS/GC is not the way to go. HPLC might be a another choice to GC. Depending on the resin's composition one of the many HPLC systems should work, normal phase, reverse phase, size exclusion, ion exclusion, etc. Somthing is sure to work. I am positiive that what you need is already in use somewhere. Hopefully, you will not have to re-invent the wheel to complete your project.
|
|
|
reply | quote |
