This may sound like an off-the-walls question, but I've got a pizza hanging on the outcome. How many analytes (compounds quantitated) are there in a "typical" HPLC assay?

Could some of you look over the assays that you do in your lab and post:
- the number of different methods run
- the average number of analytes in those methods.

Thanks in advance!

-- Tom Jupille / LC Resources

Most of my methods are specific for one or two (usually parent and metabolite) analytes.
But then I have methods specific for classes of drugs, one has 4 and the dreaded benzodiazepine method has like 12 analytes. I also have a "dump quant" method in which I dump in standards of as many drugs as I can and elute them all in 25 minutes. Usually, I dump only 6 or 7 drugs in, but I have done up to 10.

Oh and total number of methods I have..... geez, I'd have to say about 20.

Hope this helps!
Lisa

The idea in any chromatographic analysis is to look for just a few peaks of interest. Usually just one to about four-five. Anything more is diffcult to quantitate.

My personal best stands at eighteen - for amino acid analysis.

Incidentally, capillary GC analyses of compounds like petrochemicals typically separate peaks numbering thirty or more.

so much for your pizza!

rgds, srinivas/stimulus/india.

Hi,Tom! I think its very impotant if assay of your analyte is stability indicating or not. We usually have to perform successfully a stability indicating assay for up to three analytes (for example API and two preservatives) in one HPLC run.

Dr.Alex Weisman, Chemagis Ltd,Israel

Over the years I've been practicing HPLC, I've probably run at least a hundred different methods and almost all of them have been to quantify a single analyte. I can only recall about ten methods where more than one analyte was quantitated. Of these, most were used for three or less analytes.

Best Regards,

Michael Hinsberg
Hinsbar Laboratories, Inc.

http://www.hinsbarlabs.com

CDFA labs run a few thousand samples a year through about 30 LC's. We operate as a group of small labs under one management team.

From the Worker Health and Safety pesticide methods database....

14 methods, 31 compounds
13 of these methods are parent and/or metabolite separations, and the 14th one is a carbamate screen. This is largely the result of the way the studies are carried out. We really only need about 6 methods (a couple RP gradient methods, an ion-pair or two, and a very special method or three) to do the same thing--but then every analysis would be compromised somewhere. Most of these methods have been run within the last year or two.

Formulations Lab
The lions's share of pesticide formulations are now done by LC; maybe a hundred methods, many only different by the % and type of organic, most are single analyte.

Residue Lab
Most of the samples are screened using a carbamate method--10-15 compounds. Only a handful of methods for individual analytes.

Environmental Monitoring
About 20 methods. Most methods have 1 to 5 compounds. LC/MS might change everything! The first serious method has about 15 triazine compounds.

Most of the CDFA methods use RP gradient. Only formulations uses isocratic extensively. Our situation is similar to Lisa's--we either do one or two compounds, or a whole family! If we analyze the number of samples that are run thru each method, the carbamate screen has the heaviest use. However (and it's a good thing) the results are usually 'Nothing Detected'. On the other hand, there are fewer samples, but nearly every single analyte analysis requires quantitation.

So, the average analyte/method is 1 or 2, but most of our sample load is analyzed on methods built for 10-15 compounds. Probably most of those 1-2 compound methods could be combined to do more compounds, if we needed to.

Sorry--this started out to be a simple answer!

Scott Fredrickson
California Department of Food and Agriculture

Many thanks to all who responded. It looks like I'll end up having to split the pizza!

The actual bet was on the following statement: "at least 80% of HPLC methods are designed for 5 or fewer analytes".

-- Tom Jupille / LC Resources