Carryover?

<p>Hello,</p><p>I recently made several injections of a caffeine sample afterwards realizing that it was much more concentrated than expected. Now I am getting "caffeine" peaks in my blanks. I have performed a series of several needle washes (~30) and still have the peak appearing. It does appear to be decreasing within a set of replicates, but then is back to where it started when I run another set of blanks. I am assuming that there is buildup of caffeine on either the needle or in the sample loop. Is there a way to clean the system?</p><p style="height: 8pt"/><p>Thanks,</p><p>Rob</p>

Answers

  • Hello

    I would suspect the either the pre-piercing needle or the wash station oring has been contaminated. Here is some guidance, also check the procedures in the service section of the web. This is my favored method. If you have a FSE you can also call them for advice and help.

    Liz

  • Could you provide a procedure to help a user locate and remove and/or clean the wash station O-ring?

    I have seen some information that indicates contamination can be create problems if it is present in that region, but the User Guiide and the service area of the the website do not have any guidance on how to remove or inspect that region of the Sample Manager.

    Currently I am using a strong solvent mixture solution to wash the injector/loop system, but I thought it might be more effcicient if I could remove and replace that wash station block O-ring.

    RMJ

  • Following your interest, I would suggest a 2 step process.

    1. Flush the system using the Controlling Contamination procedure located in the previous posting. This will clean the O-Ring and surrounding flow path.

    2. Following the cleaning process you can remove the O-Ring and inspect it under a microsope. If you discover any nicks, or worn spots in the center sealing area this could be a breeding ground to hold contamination. Your other option is just to replace the O-Ring, this should be replaced at least once per year or more depending on usage.

    The removal/replacement procedure is attached here:

    One word of advice, after installing the O-Ring back into the Needle Wash Seal Port/Wash Station, be careful not to tighten it too much. The it could compress to a point that the needle will have difficulty traveling through it. A simple technique after installing the O-Ring is to take a Needle and insert it into the Needle Wash Port to determine if it will travel through the O-Ring.

    Best Regards,

    Dave

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