I would like to ask if anyone among you are using an HP1100 LC hooked up into a Quadrupole MS-MS. We are experiencing carryover problems with our system. Samples with >10 ng/ml levels give carryover problem to succeeding sample injections and our MS is just too sensitive and detects these carryovers, hence affecting the results of these succeeding sample injections. Did anyone among you experienced this too? The HP1100 autosampler does not seem to have the ability to allow multiple washings of the needle prior to sample injection. Nor does it allow use of variable volume for the needle solvent cleaning wash too. Can anyone please give me some advice on how to solve this problem? Is it possible to control the HP1100 autosampler to make cleaning of the needle more efficient? Would really appreciate any advice that you can give.

RTFM - the injector can be programed to perform as many wash cycles as you want. Since the injector metering plunger and syringe is part of the high pressure flow path and continuously swept with mobile phase this should minimize the carryover problem.

We use PTFE lined silicone septa because they seem to wipe the exterior of the needle better and minimize carryover.

If you use a wash vial do not cap it. Do not overfill vials - fill only half to 3/4 full. Pop out the needle seat and clean or replace. Replace injector rotor. Clean or replace the injector stator. If you have the old style injector leak pan, call Agilent and they will send you a new leakpan free of charge, this will minimize siphioning that can cause an air peak.

The spec for the injector is <0.1% carryover and we normally have none. If one of these steps dosen't fix your problem have the injector serviced. Good Luck.

I have experienced this carry over problem and have posted here on the inability of the PE Sciex Analyst 1.1 software to allow internal needle washing to eliminate/reduce this problem. I have tried ALL of the above suggestions, and they are inadequate in my case. An internal needle wash is necessary, and the sooner PE SCIEX writes the appropriate software to allow this (HP Chemstation has this feature, but Analyst overides it)the better. I have been told now by several people that they have converted to the micromass system because the software is much better, even though the hardware is not quite as good as PE. I would be happy to correspond further with you on this. You can contact me at aruda@agrenetics.com

Hi Aruda,

This message is actually posted by my colleague (There are only two of us working in our lab). The engineers are working on our system, and are trying to come up with something. The Agilent people are trying to do something with the handheld to program some wash programs. And the PE engineers have asked us to program some wash program in between the samples. However, this is not very helpful as this would increase the sample runtime, and then this would not be a "high-throughput" system! We would be happy to correspond further with you, and let you know about our solutions for the problem. Please feel free to contact me anytime. My e-mail address is aprilw@cuhk.edu.hk. I would really appreciate if there are others who could give us insights as to how to solve this problem. Thank you!