Chromatography Forum

Hello,

is it possible to manually backflush the needle seat of the Agilent 1290 Infinity II Vialsampler. We performed analyses of some sticky APIs and observed persistent carryover of those analytes in our blank samples. I've found some general procedures for other types of vialsamplers but I can't find anything specific for 1290 Infinity II Vialsampler. I've checked every manual I have. Is it possible to manually remove the needle seat with its capillary and connect it directly to the waste outlet of the switching valve of the pump and set the pump to purge as explained at the following article:

community.agilent.com/.../kp90.backflushing-the-needle-seat-of-the-agilent-vialsampler

There is no need to backflush the needle seat: assuming the carryover is caused by contaminated needle seat, cleaning the needle seat with a suitable solvent for the analyte using a squirt bottle should take care of the problem .

I've tried doing that but it didnt make any significant help. Is it possible to backflush it?

It’s very unlikely that your analyte sticks to the needle seat surface. It’s more likely the contamination comes from somewhere else? Does the carryover peak decrease when injecting blanks consecutively?

That being said, the needle seat can be back flushed by removing the needle seat and then connecting it to the capillary from the pump through a union.

It’s very unlikely that your analyte sticks to the needle seat surface. It’s more likely the contamination comes from somewhere else? Does the carryover peak decrease when injecting blanks consecutively?

That being said, the needle seat can be back flushed by removing the needle seat and then connecting it to the capillary from the pump through a union.

No, the carryover peak does not decrease when injecting blanks consecutively, but we noticed it decreases when the flow is switched from mainpass to bypass and when performing runs without injection. That's why we thought the source of carryover is our autosampler.

To confirm that the autosampler is the source of the contamination, bypass the autosampler altogether by connecting the pump directly to the column and then make injections of a blank. If the carryover disappears, the autosampler is the culprit(or the blank was not clean); If not, something else causes the carryover.

Even autosampler is the source of the problem, back flushing the needle seat will not likely solve the issue. Has the needle wash port been checked and cleaned?

Yes, the needle wash port was checked and confirmed to be working properly.

This is a TRUE, flow-through design so no back-flushing would never be needed at all.

Sounds far more like it is time to perform routine service on the Autoinjector (rotary seal). Are there any leaks? Does it pass a high-pressure test? Same for PUMP. Has the integrated degasser been professionally serviced in the last 4-years, as they can introduce contamination into the flow path?

One other area that should be addressed is to make sure you are using the needle wash system correctly. A lot of Waters users do this wrong when using an Agilent system, the design is 100% different. First comment about an Agilent A/S needle wash is that in 99% of case, you will never ever need it. So start by not using it. If you do use it, makes sure the vials with wash solution do NOT have a cap on them (to prevent contamination on the septa). Next, they must be filled with fresh solution that will 100% dissolve whatever it is that you think is sticking to the needle. This should be followed by a 'dip' and flush in another vial containing mobile phase to rinse the needle off afterwards (though, often not needed).

BTW: If you suspect something is "sticking", do not set the A/I to switch to By-Pass right after the injection completes. Leave it in the flow path, as normal,.and the whole flow path will be flushed out during the run.