1100 HPLC, Pressure Exceeds Limit at Injection- Help

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Hi Everyone,

Running 1100 HPLC with Quaternary pump and DAD. All running normal EXCEPT when sample is injected there is obviously some sort of blockage, and the pressure limit is exceeded, and pump shuts down.

Is it safe to assume that the 6-port valve has a blockage? That would be at the position where the sample is injected from the sample loop.

Before I take out the 6-port valve I just want to know if there are any other possibilities that may be causing this. IDK if the needle or sample loop can be checked verified.

Any suggestions would be helpful.


Thx.
you should be able to switch the injection valve in chemstation without injecting a sample; if you see pressure between load and inject positions differ by more than ~5 bar, then the rotor seal in the valve must be jammed
I also believe very likely that the injector rotor valve needs to be cleaned or replaced.

This is not a difficult repair. If new or unfamiliar to you, take some digital photos.

I never removed the stainless steel lines before doing this operation either. But if you do, note that the different positions are stamped with numbers. Remember that the Vespel or TZ rotor seals are considered consumables.
The very first place to check is the Needle Seat (capillary). This is first place a plug or obstruction will occur as it is where the sample passes out of the needle and into a narrower opening BEFORE going into the injector valve. We see many instances where the sample will fall out of solution and/or buffer may precipitate at this interface due to poor training, solution prep etc.

Spare needle seats, rotary seal and one needle should always be on hand. Note, the needle itself can also become clogged, but these are less common. Perform a proper maintenance service on the AutoSampler (needle seat and rotary valve seal replacement with cleaning and inspection of all A/I parts and the valve).
Multidimensional wrote:
The very first place to check is the Needle Seat (capillary).

Spare needle seats and one needle should always be on hand. Note, the needle itself can also become clogged, but these are less common.


I've had the needle actually clog, and even have had the coiled tube clog.

I ALWAYS had plenty of spare parts on hand. And spare new columns. We rarely had to call for service; my background as an auto mechanic came in handy for logical troubleshooting.
Hi Everybody,

Thanks for all the help and suggestions. I have already purchased a needle and a needle seat (eBay), I am going to try to eliminate that before moving on to the rotor seal.

I am looking at this kit online (click link) to purchase in case I have to replace the rotor seal. This is from supplymylab site. I'll update this issue as I work on it.

Again, thank you and wish everybody in this forum a Happy New Year ! ! !

https://www.supplymylab.com/Supplies/HPLC-Instrument-Parts-And-Supplies/_/Autosampler-Kits?q=2715H77&gclid=CjwKCAiA8bqOBhANEiwA-sIlN98I4JX0S7Z9xM9WH7MSixsm1T_qldiQq_HzGhKFUerETrpiphIDJxoCLMcQAvD_BwE
New spare parts are good to have on site. We always kept all of those parts on hand, all are essentially consumables.

We had the autosampler looped capillary leak at the welds, the needles leak, etc.; not that common but need to replaced then, and we needed to minimize downtime because of our cGMP tests.

It was only in the last couple of years that my supervisor deemed me "not qualified" to do such minor repairs because I didn't have an "official training certificate", even though I had taught others at our manufacturing facilities.
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Save your money and Do NOT purchase that kit. It has extra part s you do not need.
    The only Normal maintenance parts for a G1313A or G1329A/B Autosampler parts you should always have on hand are: A needle seat capillary (of the correct material and ID for your applications) and one rotary valve seal. Those are the parts that wear out and require regular replacement.

    A spare needle is also highly recommend to keep on hand (if you plug one, then you will understand as it is more cost effective to replace one than "fix" it). The arm fingers last a very long time (a few spares are OK, but usually we go 5 or more years before needing to replace them). The A/I piston seals should also last 5 or more years so not needed as spare (an injector pump hardly runs at all compared to a mobile phase pump). Additionally, the A/I pump seals are the same as used in the 1100/1200 Binary/Quat pump (because the A/I is the same pump) so no need to have spares as you should always have spare piston seals for the pump(s) available at all times. Spend the extra money on training.
    In addition to proper training in how to perform routine maintenance jobs on your HPLC system, having the most needed spare parts on-hand will save time and money.

    Here is a link to a free article which addresses this topic:
    "HPLC Maintenance & Repair Parts To Have on Hand for HPLC Systems"; https://hplctips.blogspot.com/2013/11/m ... d-for.html
    ... this is all getting a bit drastic! Before changing anything, or dismantling anything drastic, it's worth establishing what's the problem.
    It is very easy to disconnect different lines around the injection valve. First check that you know the plumbing diagram for the flow in your autosampler. The 1100 is quite a simple system. With that in mind, you can work out which connections, tubes etc. are most likely to be blocked, by checking which tubes are in use when the injection valve is in the position that's giving you a low pressure, and which are in use when it's giving a high pressure. Someone advised selecting the position of the valve without actually making an injection; this is a good diagnostic idea.
    Once you know which part of the path is blocked, you can confirm this practically. Get yourself a little Hamilton syringe attached to some normal Peek hplc tubing (you can get syringe fittings, or you can make one with a finger-tight peek connector around a 1" length of flexible tubing of roughly the same outer diameter as Peek, and an inner diameter just sufficient to fit the syringe needle; use this to seal your syringe-needle to a union, and then attach some peek tubing to the other end of the union when you want to connect it to a port, or just connect the union to bits of tubing if you want to check tubes). Undo a connection, attach your syringe via a bit of Peek, and see if you can squirt water or 50% MeOH through the tube you're aiming to test, and htat it comes out wherever the other end is. So, for example, if you're testing an Agilent 1100 and you think the needle seat might be blocked, raise the needle, take the connection from needle seat to injection valve out of the injection valve, attach it to your syringe, and see if you can push liquid back up out of the needle seat. It should flow easily. If it doesn't, the seat is blocked. You can do this systematically for the whole of the region that you suspect might be blocked. The most likely locations are the needle seat and the connections to the injection valve (not the valve rotor itself, curiously). Dirt gets stuck at restrictions and places where it goes round corners. While you're doing this, be aware of leaks too, ready for when you encounter a system which is managing to stay under the pressure limit by leaking! But almost certainly not in this case!
    You will often find that reverse-flushing tubing will get rid of minor blockages. If not, at least you'll know for sure which part is blocked and needs replacement. Merely assuming that the blockage is somewhere because it usually is can be a frustrating way to fix things.
    Wear safety specs when pushing solvent through things with a syringe. When they're blocked, and you're trying to see if a blockages is serious or clearable by back-flushing ferociously, if the syringe slips it will spray you in the face with its contents.
    But honestly: do test which bit gets blocked. It's quite quick undoing a few connectors to test, and a lot less hassle than changing parts, let alone disassembling a valve (which is almost never necessary).
    Above response demonstrates why my experience as a mechanic during college came in handy in the analytical chemistry lab !!! Logical troubleshooting, folks.

    Isolate and conquer.
    [quote="trozen"]you should be able to switch the injection valve in chemstation without injecting a sample; if you see pressure between load and inject positions differ by more than ~5 bar, then the rotor seal in the valve must be jammed[/quote

    Always note the delta bar value between load and inject as trozen suggested, this is great advice. I also agree this value should be 3-5 bar max at 1ml/min in inject mode (includes needle, seat loop and rotor seal)

    Since the needle is part of the flow path you have a partial blockage in the rotor seal, needle, loop or seat.
    Move the needle into maintenance position, this isolates it from the seat. Remove the pump out capillary (port 1)and connect it directly to the needle seat capillary with a union. ( Inject valve no longer in flow path) run 1 ml/min with water you should observe a stream shooting straight up and out of the seat. (Have paper towels ready) if stream is irregular and sputtering, you found the parrtially clogged component.
    Note the pressure contribution before and after this step.
    Do the same with loop and needle using the pump out capillary. ( connect capillary directly to loop, then to needle) Each of those 4 components should be contributing about 1 bar each maximum. In most cases the rotor seal or needle is the issue as others suggested.
    A sampler pm will likely fix but better to understand how to divide and conquer this common hplc problem.

    Examine bad rotor seal under a 40x jewelers loupe, the groove that connects to the sample loop can have crud causing high pressure and area RSD issues.
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