So recently weve been using a GC but we have a problem: we always get contamination from previous samples, although we rinse the syringe several times (between 15 and 20 times) with the solvent, some sample leftover is carried on for the next measure. We can only do manual injection since the automated sampler got screwed. Any of you who have used a GC manually has had this issue?, how do you clean your syringe between samples?
Thank you
@Jhon S Wishnok thank you, will try removing the plunger , but using vacuum would be difficult.
Some general comments.
- Why do you think the issue is with the syringe? What you describe (contamination from carry-over) could also be caused by a fouled column, worn or contaminated injector valve (or liner). Have the injector serviced. This is routine maintenance.
- You may be overloading the system with sample. Verify that the sample concentration injected is appropriate for your selected injector, column and method. If possible, reduce the concentration by 10 fold or run a loading study.
- Rinse the manual injector with a suitable solvent several times before use.
- Rinse the syringe in a suitable solvent (or solvent mixture) that is know to 100% dissolve the samples. Then wash for next use.
- Use new glass syringes with Teflon plungers.
- Buy spare syringes (they wear out and it is less expensive to dispose of them at some point then to spend hours cleaning and/or running samples where the data can not be used).
- Is your GC autoinjector still inline? If so, it may be worn and/or contaminated adding to the problem. Have it serviced.
Someone should be in charge of maintaining this analytical instrument and also supervising training and use to prevent damage. Have you contacted an experienced chromatographer at your school for help?
Please look at the following below links which may help you in your analysis:
https://www.agilent.com/cs/library/eseminars/public/Webinar_Sample_Introduction_Simon_May_9_2018.pdf
http://kinesis-usa.com/media/wysiwyg/knowledebase/pdf/SGE-Syringe-Selection-Guide1.pdf
http://www.analab.com.tw/upload/adlist/201611/Syringe%20and%20Needle%20Catalog.pdf
Thanks
Thank you, UPDATE: I ran the chromatograph with no sample or solvent at all, and still got contamination, so we verified that the column is overloaded and contaminated with sample. We ran a method with injector T of 240°C and oven ramp of 200 to 220°C in the hope that it could be cleansed, to no avail. Any more suggestions? we might try a different solvent which might clean the column, but I'm not sure that it is going work.
I think u must clean it with the same solvent of the sample after that clean it with methanol and dry it
Depending on the type of column, you could cut about 10 cm or so off the injector end. Often times columns will get contamination right at the entrance. Also, as others have said, replace/clean the liner and septum, and give the injector port a good scrub with a methanol-soaked cotton swab.
As noted above; "Have the injector serviced. This is routine maintenance."
Also, please find someone local to provide GC training to the users. *Basic GC training should include basic maintenance procedures too. GC Maintenance procedures can be taught and used by anyone familiar with the instrument operation in a few days, but GC method development takes a few years to learn.
For manual Gas Chromatography injection, it is very much essential to clean the GC syringe. After several injections, you have to take off the syringe and ringe with methanol. I think, ringe is the best way.
Hi. First with the solvent you used in preparing the sample then with the solution of the sample 3 times.
I think you should clean it with the same solvent as the sample after it is cleaned with methanol and dried several times
- Badges
- Science topic
- Similar topics
- Phytochemistry
- Extracts