Chromatography Forum

By fangwang on Monday, August 23, 2004 - 02:08 am:

Dear all,
I am sorry about creating a new conversation here while I already posted my problem in "Peak in blank reagent after derivatization". The reason is that I really need the suggestion from all of you. I did contaminate the autosampler with my derivative so even I inject the mobile phase, it still shows a peak but if I connect another loop injector, this peak disappears. HW Mueller and Consumer Products Guy suggested me to clean the autosampler but I don't have any idea how to clean it properly! I flush whole system with IPA and HNO3 already but the contamination is still somewhere in autosampler. Could anyone show me the good procedure to clean the autosampler (including taking it out and cleaning manually)? I really need to get rid of it ASAP because the time for my project almost run out.
Thanks in advance!

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By Consumer Products Guy on Monday, August 23, 2004 - 07:52 am:

First I'd try a new rotor seal (are you using vespel or tefzel?), and flush with solvent stronger than IPA, such as ACN, THF. I physically have removed the stainless steel lines and made up fittings adapters and have flushed from a 10 cc syringe with a luer-lock fitting that has a 1/16 inch needle, to which I swaged HPLC nut/ferrule.

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By anon on Monday, August 23, 2004 - 12:28 pm:

first, i would confirm that it's caused by the ALS. Plumb the system bypassing the ALS, then run several blank gradients to confirm that the peak is not there !. then, change one part at a time to see where the peak goes away....

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By ingochrist on Saturday, August 28, 2004 - 02:13 pm:

What type of autosampler do you use?

Is your syringe/needle clean? If your autosampler has a needle wash system you may need to purge the system a few times. As someone else previously asked, what type of autosampler do you have?

Sorry for delayed response, I am too busy with my project. My autosampler is Agilent 1100 series and I found out that my needle seat was contaminated. Now I clean the needle seat everyday by injecting several sovents (ACN. MeOH) at the end of the day and I am working with very low concentration now so not worrying about the contamination again. Anyway, do any of you have better method to flush the Agilent autosampler (needle and needle wash) because Agilent doesn't have a good design for everyday washing of thes parts?

I have used the HP1050 which is similar if not identical. If you use an MeCN wash at the end of the sequence this should wash it nicely along with your column. Wash the system before you start your samples too.
About 20-30mls of solvent each time should keep it clean.
I had no problems over 10years.
Perhaps your samples need diluting too - they might be too concentrated.