Hi To Everyone,
I am a 1st time poster here, so apologies in advance if this topic has been covered in the past.

I have been asked to set-up and improve our HPLC System Monitoring, and am wondering if the paramaters that I am about to list are considered a comprehensive enough renage of factors to give good indication to how our application is performing.

At present we only measure Peak Area, Peak Width(50% Height), Retention time and Component Concentration.

As part of my proposal I have suggested monitoring Peak Retention Time, Peak Start Time, Peak End Time, Peak Height, Peak Width at both 50% and 4.4% Height, K', Column Selectivity, Asymmetry Ratio, Plate Number using 5-Sigma method, and Resolution Ratio.

I have only 18 months HPLC experience to date, therefore any feedback, comments or such from my Peers would be very gratefully received.
Thank You all in advance!

Kris

Do not think that by monitoring more you have made your process better! A spreadsheet of numbers that no one will utilize is just busy work. What parameters will give you information that your process has changed?

KEEP IT SIMPLE...

I agree with the previous reply. Keep it simple!
Peak area is definitely important, but even retention time is not the important issue. The important part is resolution from neighboring peaks. Peak asymmetry and plate count are only important, if they affect quantitation and resolution. If they do not affect either, you can nearly ignore them..

Greetings Kris,

First of all, welcome to the forum. I have been using these boards for a little over two years now and have learned and been able to teach a great deal. Even if one doesn't have a question currently, I have found them to be quite useful simply as a learning tool. I hope you do, too. :)

In answer to your question, definitely keep it simple. Identify what your needs are and build your system based on what you need and fill in with what is lacking. Don't be afraid to be honest with yourself and the other people in your lab. If no one is ever going to use peak width at 4.4% and 50% height, don't track them.

For example, I usually use peak area, peak asymmetry, resolution (only if there is more than one peak of interest, of course), and retention time (less important, but can be an indicator of problems with organic ratio, among other things). Other factors are important based on the type of chromatography I'm performing. K' may be important if you have a weakly retained molecule and want to track where it elutes in order to set up a specification.

Hi Kris,

I guess I will disagree with the keep it simple consensus above. I work in the pharmaceutical industry and we normally perform replicate standard injections and have to meet system suitability requirements. This system suitability report can be kept simple and is just used to tell you whether you have a valid run or not. However, the system suitability report is not usually detailed enough to provide a useful starting point for troubleshooting or training.

I also like to make available a more detailed system performance report that details many more parameters. For example, in a normally functioning HPLC system, the %RSD of the height and area will normally be small and approximately equal. Many injector problems will be evident by a larger than normal but still approximately equal %RSD of height and area. Pumping problems often show %RSD area > %RSD height, mobile phase or gradient proportioning valve problems can often be identified be %RSD height > %RSD area, etc. Overload vs tailing can be identified at lower levels using statistical moments.

I think the modern data systems make is so easy to summarize and give statistical reports based on replicate injections it would be a shame to not learn to utilize these capabilities. Having a detailed performance report available makes it easier for the senior chromatographers to hold impromptu training at the bench and will also help the inquisitive junior chemist develop better intuition faster. If you are going to provide a detailed report it would probably be worth your time to provide some training on ways to use the additional data. Good luck.

Actually, Tom is right. Monitoring many different things is important, and you will be able to troubleshoot. My previous comment was more geared towards setting specs for a properly functioning system. This is the part that I think is worth keeping to a minimum.

Tom, thanks for again pointing out some correlations that not everyone has constantly present in ones head. However, I am a little puzzled by the use of %RSD. For instance:
On the injector: It is necessary to check whether a substance has the tendency to carry over (in the injector....) before you start your analysis by injecting water, etc. (blank), and later for additional checks. If you loose substance (out the front of the injector.....) you can see it immediatly in the area (A) or hight (H) of a Int. St., if the loss is larger than acceptable.
On the pump and gradient valve: These are immediatly evident by rt changes or A or H, A/H and by routine flow rate measurements (flow meter not calcs from pump frequency).
On overload vs tailing: Thatīs also an issue that can be settled in method development. Sep. problems where you have to operate near overload should be extremely rare.
So what and why do you need more than:
Flow rate, rt, A, H, N, Assymetry..., Resolution, maybe S/N and occ. blank inj. to keep it up?

Or asked differently, is there still no (integration) software which shuts off the HPLC when peak characteristics change? (I am only interested in software which can handle a radio-detector, there seems to be none which can do this)

I guess the question is: Do you want to monitor a quick test that will let you know if your instrument should be used for your analysis of the day OR do you want to monitor how your instrument performs the critical analysis?

The answers for the first would be keep it simple (As HW Mueller stated). Obviously the second you may want more depending on what your analysis requires (Tom Misukami's needs)

Thanks to everyone who has taken the time to reply to me, and thanks to David for the kind welcome.
I have gained a lot from this thread, and have gone away to consider our system.
I last week attended a one day seminar by a company local to me and the also mentioned %RSD as a robustness tool, so this is something that we have never looked at before, and will investigate the characteristic along with the others.
I gaurantee you will be seeing me again shortly! :o)

Goodbye for now!