I have a HPLC LC-10AS pump thru which I pump
a 0.5 mM phosphate buffer along with methanol.
I must say that I've never seen an HPLC pump
eat the seals (and sometimes the sapphire
piston) the way I have with these Shimadzu
pumps. Shimadzu's response has been that this
is the cost of running a buffer thru our pumps.

These pumps run about 40 hours a week and I
only average about 80 hours of use before the
seals need to be replaced and about 160 hours
before the piston has to be replaced. After
watching the Shimadzu service rep replace these
items several times over the past year, I have
become quite proficient at replacing them myself
since the warranty expired. But $40 for the
seals and another $140 for the piston is getting
damn expensive. Anybody else had this problem?

Footnote: I know of another facility that runs
the same buffer/methanol mix in their Waters
HPLC pumps and they don't have this problem of
constant maintenance. Should I dump the Shimadzu
pumps altogether and buy something more rugged?
Anyone know of an after-market supplier of
more rugged seals/pistons?

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I never had this problem with any system I ran which includes LDC-Milton Roy, Hitachi, HP, Shimadzu, and Waters.

We currently have five Shimadzu ternary (high pressure mixing) systems in our lab. They are very dependable. We typically run using a mobile phase of 15, 20, or 30 mM potassium or ammonium phosphate in methanol/water or acetonitrile/water. Our systems normally run 24 hours a day. Replacing seals every 80 hours and pistons every 160 hours sounds very suspicious to me. Especially using a 0.5 mM buffer. We change our seals once a year during our preventative maintenance and in addition maybe a couple of times during the year. The only time we lost a piston, was when someone hit it when the pump head was removed. I did see a damaged piston once at another company where the LC was used and really abused. This was an exception regardless of brand.

To help prevent this problem in any system, if you are not going to be running samples but need to keep system equilibrated and in a "ready" state, turn your flow down to something like 0.1 mL /min during this time. Don't just turn the pumps off. This will keep the back end of the piston "wet" and constantly "wiped", thus preventing crystallization of the buffer on the piston, which can score your seals. Also when you are ready to turn the system off, even if just overnight, flush the system first with 50/50 methanol /water or acetonitrile /water, followed by 100% methanol or acetonitrile respectively. These procedures are especially important when using high salt concentration mobile phases.

If you still think that it's the brand of seals or pistons you are using, just switch brands. Optimize Technologies has a seal rated for over 3,000 hours of continuous use. That should solve your problem. It has nothing to do with the rest of the pump.

Suggestions:

1) Plumb & use the backwash ports provided to allow gravity to flush between the seals (DI) while running.

2) Program a dedicated "flush" file using a solvent switch box to pump some organic/water (no buffer) through the system after each run.
2a)If you do not have a solvent switch box, get one - they're cheaper than new pumps.
2b) Plumb the switch box between the solvent jugs and the degasser ad they do suck a little air into the lines.

3) Optimize Technologies makes good seals - one part fits all (pump & backwash). If you use them on a pump w/ the little teflon spacers (newer Shimadzu - ie LC10AT)- don't use the little spacers. They also sell replacement plungers, kits, check valves etc. for reasonable prices.

If your buffer is too corrosive you could install a seal washing system
This can be as easy as conencting a reservoir that drips 5 t to 10 drops of water in the back of the pump head.
The LC-10AS has a conector for tubbing on the top of the pump head, and an exit connector in the bottom that can be plumbed to the discard.
We had the same problem and got excellent results with this system.
If you are a little bit more techniclly inclined. You can also purchase a small peristaltic pump. This way you do not need the reservoir on top of your pump.
And you have the flow always at the same rate.

Hope it works

Flushing behind the pump heads with the seal wash is a good idea. Make sure you wash the buffer out of the system when you are not using the pump (just replace the buffer with water and pump the same organic/buffer mixture).

We use 10AD pumps and found that there was a mismatch in the seals we were using and the pistons. Shimadzu makes sapphire and ceramic pistons, and they use different seals. We were eating up seals when we used the wrong combo. Check with Shimadzu for the right combination for your pump.

Is the amount of buffer you mentioned correct? 0.5 mM is so little as to be almost worthless (and it would have very little corrosive effect). If, on the other hand, you meant to say 0.5 M, that's a HUGE amount of buffer. More typical ranges would be 20 - 50 mM (0.02 - 0.05 M).

It is very rare that pistons need to be changed that frequently, even if the buffer concentration is 0.5M. If your buffer is 0.5mM then you have a service problem or a seal-quality problem.

What salt are you using?, what pH is your mobile phase. I have used mobile phases as corrosive as 0.1M HClO4 and the seals resisted that very well.

The piston -wash attachment can help, but with such corrosive buffer or poor quality seals, it may not be good enough. I recommend you try a different seal material, or perhaps a modification of your method to use a different buffer.

I have had to deal with a similiar situation in the past. This problem may not be reflective of Shimadzu pumps, (which are typically as rugged as the next) but may be more indicitive of the type of MP you are using. I had similiar, and severely inconvenient, breakdowns of both seals and pistons on a Waters model pump. The problem, however, was in the constituation of the mobile phase. Depending on your organic ratio, you may be causing the buffering salt to precipitate. A good practice would be to flush your system after each extended use with the same ratio of MeOH/H2O as in your method. Gradually increase the Organic phase (which can be accomplished via a simple gradient) to about 70/30 MeOH/H2O (run it for about an hour at the operational flow rate). The RP column also can be stored under these conditions until the system is needed again so there is no need to disconnect the column from the system.