Forcing Integration parameters

[mbicking]

lmh:
I think we are all in agreement on these things. I wish there was a better computational way to resolve these issues, ... but then I wish all my peaks were perfectly separated in less than three minutes also. Ah, the real world...!

One of the problems is that there is little information to guide the practicing analyst on how to do things. There are very few mentors in the lab anymore; it seems that's what this board has become. So, everyone does what they have always done, but nobody remembers why any more.

Many analysts don't even understand that poor resolution can mean some kind of potential integration error. And too few labs are equipped, or even allowed, to make changes in the methods to solve these problems. We seem to be propagating bad practice in too many cases.

Hoping for a "resolution" to this problem some day!

[lmh]

that's a good perspective. It's very true: there's a real shortage of expertise in the lab. I don't know which is worse, those of us who lack the training and have had to pick it up as we go along (highly dangerous - gappy knowledge & misunderstandings likely), or those who have had the instructions, and now merely follow them blindly without thinking about what they are doing (something that is encouraged in a work environment where change is anathema).

I'm very grateful to a number of people who've put their life's experience into websites and e-books (and a few "real" books that I've managed to buy), and to those who give such good answers on sites like this.

It's unfortunate that formal training in hplc is so very expensive, and of variable quality. Usually the training we get centres entirely around software, and "little" things like what a calibration curve should look like, repeatability of results, analytical versus sample variation, and the values of LOQ etc. get squeezed into "by the way, our software also has features to help you do this, if you really need to for QC purposes".

Ah well, things can only get better...

[mbicking]

lmh:

It's unfortunate that formal training in hplc is so very expensive, and of variable quality.

Are you trying to bait us? I'm sure you know that both Tom and I (and some others here) provide HPLC training. We would be happy to discuss your needs in more detail.

Have a good day!

[mbicking]

lmh:

It's unfortunate that formal training in hplc is so very expensive, and of variable quality.

Are you trying to bait us? I'm sure you know that both Tom and I (and some others here) provide HPLC training. We would be happy to discuss your needs in more detail.

Have a good day!

[skunked_once]

It's unfortunate that formal training in hplc is so very expensive, and of variable quality.

My experiences after attending several training sessions in various aspects of chromatography is that they run the whole gamut from being vendor commercials to excellent, unbiased presentations . It all depended on who was sponsoring the training and who was making the presentations. Kudos to those of you who do a good job.

Ah well, things can only get better...

One can only hope

[Peter Apps]

I wonder if there is a difference between HPLC and GC in the optimum strategy ? In GC there are lots of plates, and detectors that are either very non-selective with wide dymanic ranges (FID, full scan EI-MS), or very selective (ECD, FPD, SIM-MS) but the selectivity of capillary column stationary phases is quite limited, and gas is gas. In HPLC plates are fewer, detectors are more selective than and FID or full scan MS, but not (except maybe for fluorescence and certainly for HPLC-MS) as selective as the selctive GC detectors, and they have smaller dynamic ranges. The range of stationary phases is probably roughly similar (although there is no GC equivalent of normal vs reverse phase) but you can do all sorts of things with the mobile phase.

So in GC with a non-selective detector you can have a tiny peak riding the tail of one a million times bigger, or you can (if you are lucky) use a selective detector so as not to see the interference. The slopes of the peaks are very sharp, which sounds good but has the disadvantage that small changes in resolution, or in the size of the major peak, have substantial impact on the "baseline" of the minor target peak. In HPLC the maximum difference in the size of the peaks is smaller, and their slopes are gentler, which means that the equivalent changes in resolution or relative peak size have less impact on the "baseline" of the minor peak. Integration in HPLC (and in packed column GC with non-selective detection) should then be more robust to sample composition than it would be in capillary GC.

In either case, if the target analyte peak is riding the slope of another peak I would like to validate the method over a range of sample compositions, and do the calibration by addition to real matrices.

Peter

[lmh]

mbicking, oh, nooo! I wouldn't want to offend anyone on this site. Half the point is that people like you and Tom who write such full replies to questions here are offering a free dissemination of knowledge on top of your training.

No, I was just refering to the more general problem that if a lab is short of cash and looking at inviting a trainer in, inevitably the cost is high, so the training gets cut as short as possible (too many themes to cover in too short a time), and you rarely know in advance just how good the trainer will be. There are some really superb trainers and courses out there, and some that are perhaps a little less optimal, but until you've blown £1000 trying one out, you have no idea which you are going to get!

There's also the problem of knowing what to ask for. In order to choose a course, convince management we need it, or advise a trainer on what we'd like to be trained in, we have to know what it is we don't know and ought to know. Since we often haven't a clue, we often remain in ignorance.