Why are my check valves dying?

[Mattias]

We are actually OK now! No failed check valves for weeks.

I installed new ceramic check valves in all Alliance systems, and they seem to work. I have also told the technicians to take new check valves, instead of washing them, when they start to go bad. A failed sequence costs more than a couple of check valves.

We have not introduced any filtration. I also do not believe in filtration if you have high grade chemicals to start with. I think your rather add particles than remove them...

[Johnny Rod]

Filtration seems to be a moot point. As you say, the purity of solvents these days is very good, and there is thinking that the operations of filtration just expose the MP to more glassware, detergent residues etc. (as we are in a non-ideal world). I would say don't worry unles you are making buffers, in which case maybe filter... definitive eh?

[biochemist]

Recently, I have noticed that a well-known OEM-Manufacturerer and HPLC-Supplier also offers Check-Valves for the Waters Alliance System. I have no experience with this parts, but it my worth to try a alternative source for check-valves.

I'm in the pharma industry. Could I check what kind of change control or requalification tests (if any) are necessary for switching out a(n admittedly lousy) part like this?

[Mattias]

Recently, I have noticed that a well-known OEM-Manufacturerer and HPLC-Supplier also offers Check-Valves for the Waters Alliance System. I have no experience with this parts, but it my worth to try a alternative source for check-valves.

I'm in the pharma industry. Could I check what kind of change control or requalification tests (if any) are necessary for switching out a(n admittedly lousy) part like this?

I am also in a regulated environment. We do not perform any requalification when changing check valves, or type of check valves. If we need to do that, we can close this lab.

[tom jupille]

The issues with acetonitrile and sapphire check valves have been around for quite a while:
http://www.chromatographyonline.com/lcg ... ail/524647

[Johnny Rod]

I would say you do the same verification checks after changing them as if you were changing them for the same ones. If you normally do nothing then do nothing, or maybe do whatever is in your regular pump performance verification programme.

[Jack Silver]

We are actually OK now! No failed check valves for weeks.

I installed new ceramic check valves in all Alliance systems, and they seem to work. I have also told the technicians to take new check valves, instead of washing them, when they start to go bad. A failed sequence costs more than a couple of check valves.

We have not introduced any filtration. I also do not believe in filtration if you have high grade chemicals to start with. I think your rather add particles than remove them...

My experience is that the chemicals may have been high-grade, but the bottles weren't washed well. I thought the same thing as you until I saw what was in the filter after filtering solvents- fibers, I saw them with every bottle of solvent. We ran semi-prep scale, so we would filter 4 liters at a time.

I also worked for one of the companies that supplies bottles to the chemical industry. Unless the customer specifically asked (and paid for the service), we never washed the bottles. Although they came out of the mold and Lehr (annealing oven) clean, they would sit in a dusty warehouse without caps many months before being shipped. It was up to the solvent bottler to clean the containers before filling.

[Hollow]

We are actually OK now! No failed check valves for weeks.

I installed new ceramic check valves in all Alliance systems, and they seem to work. I have also told the technicians to take new check valves, instead of washing them, when they start to go bad. A failed sequence costs more than a couple of check valves.

we once had also changed to ceramic ones but actually we're back to standard ones.
Instead, we introduced the practice of purging the system with methanol before shutdown. Few check valve issues since doing so.

And we don't filter our mobile phase, unless it's a buffer.

[HPLCaddict]

We do not prefilter any mobile phases, may they contain buffers or not. There are these standard inline-filters on the ends of the eluent lines, which are good for filtering bigger particles. Whenever possible, we premix eluents and don't use pure acetonitrile. Attention is paid to never let a system stand that's been running on buffer-containing mobile phases. Either it is flushed buffer-free after analysis or let run on a low flow-rate. Check-valves are cleaned once a year during PM.
With these working practices, I don't see check-valves malfunctioning during a sequence. There actually is occurence of a sticky check-valve once in a while, but only when using a machine that's been idle. Usually after a short visit to the ultrasonic bath everything's fine again.

[juddc]

Hmmm...oddly enough, I have a 6 year old 2695 next to me happily pumping neat ACN at 1.2ml/min with no difficulty at all ( ~15 psi ripple at 2350 psi) using ruby check valves. I have a drawer full of old check valves, some ruby, some ceramic, and they're all fine. In my 20 years of experience with Waters instrumentation, I've not seen a problem with premature check valve failure that couldn't be traced to an issue with the procedure in question.

My basic rule of thumb is similar to that of CPG and others: Filter all mobile phases into which a solid has been dissolved. Trusting your reagent manufacturer or the last guy that opened the bottle is a fool's bet in my opinion.

I have seen this type of failure occur, however rarely, and assuming that your reagents are OK I'd look at the quality of your deionized water. An HPLC - ANY HPLC - is something of a canary in the coal mine when it comes to water quality. If the water's getting funky, your LC is going to tell you and it'll tell you in several ways. If something is coming out of the water in the presence of ACN and coating the check valves, then you're going to have problems. Having salts added to the MP could exacerbate the issue.

What happens when you try to pump your MP without buffer salts?

[Klaus I.]

Hmmm...oddly enough, I have a 6 year old 2695 next to me happily pumping neat ACN at 1.2ml/min with no difficulty at all ( ~15 psi ripple at 2350 psi) using ruby check valves. I have a drawer full of old check valves, some ruby, some ceramic, and they're all fine. In my 20 years of experience with Waters instrumentation, I've not seen a problem with premature check valve failure that couldn't be traced to an issue with the procedure in question.

I think this is quite interessting, what buffers do you use and how often you are changing the buffer?

[juddc]

Buffers? Well, I try to stay away from phosphate buffers if at all possible and if I do need to use them, I use the postassium or ammonium salts because of their greater solubility. I use ammonium acetate, ammonium formate, phosphoric acid if a low pH is needed, TFA (or other perfluorinated acid), and I try to keep my concentrations as low as possible. I do have the luxury of being the only guy that works with HPLC, so I have absolute control and responsibility for my instrumentation.

Cheers!

cj

[Wormwood]

I had exactly the same problem when in a former job at a CRO. We'd just bought 3 new alliances in to meet a particular customers needs. In short order we'd notched up 6 service engineer visits in a month. When challenged as to why the check valves kept sticking he replied 'our check valves aren't designed for use with acetonitrile'

I've always avoided Waters like the plague after that.

[biochemist]

Anyone else notice a trend?

We have been using the same Alliance machines since 2005, and only started having serious issues with the check valves in the last ~3 years.

We have been using both 100% acetonitrile, acetonitrile-TFA, and phosphate/chloride/acetate-containing buffers since the beginning, and haven't changed our mobile phase preparation procedures. We carry out yearly PM where the check valves are changed.

PS : Our instruments are not in use between projects, and our check valves stick most often when bringing an instrument out of an idle state. There are less problems when we operate them continuously.

[wormwoody]

Anyone else notice a trend?

We have been using the same Alliance machines since 2005, and only started having serious issues with the check valves in the last ~3 years.

We have been using both 100% acetonitrile, acetonitrile-TFA, and phosphate/chloride/acetate-containing buffers since the beginning, and haven't changed our mobile phase preparation procedures. We carry out yearly PM where the check valves are changed.

PS : Our instruments are not in use between projects, and our check valves stick most often when bringing an instrument out of an idle state. There are less problems when we operate them continuously.

This would actually tie in with my own experience, our instruments always seemed to encounter the most problems when acetonitrile had been in the solvent lines but no flow was on.