Pump Problem with Acetonitrile

[syx]

Dear member,
Does anyone here who use Shimadzu LC-20 AD or LC-20 AD XR ever get pressure problem when the pump used to deliver acetonitrile? We have both type in our UFLC system, the both have same problem. I have discussed with the technician and they said if they never found this condition elsewhere. They offered Nexera to avoid acetonitrile, so I think this new system would not be suitable for method that using acetonitrile in mobile phase.
I have read John Dolan's article in LCGC magazine for the reason why this problem could be occured. In order to avoid the pressure problem we should pre-mix the acetonitrile with buffer solution. This method is not efficient, since acetonitrile will be wasted a lot and could not be use for different method.
We need more reliable system that could deliver acetonitrile without problem. Any suggestion?
Thanks in advance.

Regards,
Siswanto

[Bintang]

Exactly what is the problem?
We have these pumps and use them frequently with pure acetonitrile without ever having any problems. It could be that you are using bad piston sealings that can not tolerate organic solvents (back at Uni we had some old Bischoff pumps where you had to have different sealings for different solvents). Original sealings from Schimadzu can run any solvent but they are dreadfully expensive.
Are you using them for Ultra high pressure? the ones we have are maximum 400bar.

[DR]

Look into ceramic cartridge check valves if the shimadzu ones are ruby/sapphire.
Also - if you don't leave the pump heads in acetonitrile between runs, you may encounter fewer problems.

[syx]

it is pressure problem. the problem will be occurred after the pump was run for several time. we had isolated the problem and found that it is happened on the pump which deliver acetonitrile.

[Bintang]

I still do not understand what the problem is do the pressure go up or down?
I guess it goes down, then your problem is most likely the piston sealings. That you see the problem with acetonitrile is due to its low viscosity.
If you have been using phosphate buffer in the system before you switch to acetonitrile you have to wash it very very thoroughly or phosphate will percipitate and ruin your pistons, sealings and or clogg your check valves.
When runing 1% amonium hydroxide eluent I did get problems with the check valve on the mixing chamber otherwise I have never had any problems with the Schimadzu checkvalves so I would say they are fairly robust.

[syx]

dear bintang, the pressure will be very unstable, tends to drop.
your system is binary or quaternary? the problem was occurred on the pump that deliver acetonitrile, in the binary system. I never found this problem in our quaternary system.
I have found condition that could reduce or eliminate this problem as mentioned in Dolan's article: using active inlet check valve or using check valve that be made of materials other than sapphire and ruby (e.g., sintered ceramics, comprising alumina oxide or zirconia oxide).

[lynzjm]

If your pressure is unstable and tends to drop i agree it is probably an issue with something like the pistons seals, you shouldnt get a drop in pressure unless there is a leak somewhere or air bubbles being introduced. I'd try changing your seals and then running some e.g. IPA down the line to give it a good clean as well. Also check your degasser is functioning properly, our old one on our Dionex system went and the first indication was pressure fluctuations due to it introducing air into the system and confusing the hell out of us trying to figure out what it was and it was as it was only evident on methods which used multiple lines as the switch was when it decided to introduce air!

lynz

[unmgvar]

what type of containers do you use for the Acetonitrile?
glass, aluminum, coated SST?

[Sallybeetle]

In the past, with different brands and ages of HPLC, I had to buy check valves that were made to work with higher concentrations of Acetonitrile. The HPLCs would experience a range of symptoms depending upon the mobile phase and pump model.

[syx]

If your pressure is unstable and tends to drop i agree it is probably an issue with something like the pistons seals, you shouldnt get a drop in pressure unless there is a leak somewhere or air bubbles being introduced.

the problem started to occur about 3 months after installation.
we have 2 UFLC systems, or in other words, 4 pumps.
the problem only occurred in each pump which was deliver 100% acetonitrile, and will be gone after we change the acetonitrile with methanol, water, or pre-blended acetonitrile with other mobile phase component.

by those facts, we conclude that there is something between pure acetonitrile with check-valve or piston-seal.
after we read the LC-troubleshooting article, as I mentioned in previous post, we are sure that the problem should be due to 'interaction' between acetonitrile with ball valve.

what type of containers do you use for the Acetonitrile?
glass, aluminum, coated SST?

we use lab bottle as the container.

In the past, with different brands and ages of HPLC, I had to buy check valves that were made to work with higher concentrations of Acetonitrile.

I found that waters has check-valves using ceramic ball. Agilent 1260 use active inlet valve. it will be reduced or eliminate this problem.

[unmgvar]

is your instrument old?
or maybe it is connected to the application you are running there with buffers?

i simply today was in a lab where they have an old machine, a summit dionex, and i know them for a while, and suddenly today when they ran the machine with 100% acetonitrile they got pressure flux just like you. the instrument is 4 years old.
the moment we went to a little water mix the pressure got away
and it reminded me of something and this is maybe your case
in some cases the check valve material start to get static charges inside of it when running 100 acetonitrile.
cleaning or renewing the check valve or changing the type of check vale material should solve the problem

and also never trust a technician that swears to you that a problem never ever occurred before that in an HPLC

[syx]

the UFLC systems are new and the problem was occurred about 3 months after installation. I am sure it is the same problem with yours and you're right that the technician swears this is new problem for them and they never found the same problem before.
do you have any information about the most common HPLC in the world? when I offer to purchase new LC system from Agilent, my colleague manager said that Agilent is not good, rarely used, not reliable, blah blah blah... I am interested Agilent 1260 because it uses active inlet valve. Alternatively, I can use Waters', that supplies check valve with ceramic ball.

[unmgvar]

did you take apart the check valves for clean up?
did you change the check valve cartridge to a new one?
Shimadzu will also be capable of providing another type of check valves, all companies can get different types, after all they design the casing and dimensions according to what the companies that do check valves have.

i do not know what goes in Indonesia for HPLC support but worlwide, waters and agilent have each around 30% sells of the HPLCs, Dionex are a very big third, shimadzu and Thermo are 4th and 5th.
still all systems can perform and do about 99.99% of the same stuff, what you need is to know your hardware little bugs or needs of maintenance.
it looks like your tech support is not that good. tech support and first training on the HPLC will tell how happy you are with the instrument after they brake down, and they all brake down.

try to change the check valves first, in the end shimadzu HPLC is as good as the others in term of use.
today's main differences is in the software and service

[syx]

did you take apart the check valves for clean up?
did you change the check valve cartridge to a new one?

the answers are 'no' and 'no'. when the problem was occurred, we just let it deliver water and the problem would be run away. what we do to avoid the problem now is to pre-blend acetonitrile with several portion of other mobile phase component (i.e., buffer solution or water).

i do not know what goes in Indonesia for HPLC support but worlwide, waters and agilent have each around 30% sells of the HPLCs, Dionex are a very big third, shimadzu and Thermo are 4th and 5th.

thanks for the information. do you have the data or literature or link? I want to show it to my colleague and let him know what Agilent is...

try to change the check valves first, in the end shimadzu HPLC is as good as the others in term of use. today's main differences is in the software and service

I have asked to shimadzu support in indonesia about other check valve. however, there is still no answer. but I will try to remind them about my question and requirement.

[Hfranz]

100% ACN used in binary pumps is a classic. John Dolan's article covers it quite well. It is also true that ceramic check valves are more reliable. However, this is in vain if the ACN quality in not good enough. You would be surprized how much even comparable qualities of different brand differ. It is also no surprize that you do not observe problems with your quaternary pumps. By design, these pumps mix prior to the check valve, so it is not permanently in contact with 100% ACN as with binary pumps. So my recommendation is to try different suppliers and qualities of ACN.