Help! Area counts from lab to lab 1000x different

[chandled]

I am using an Agilent 1200 HPLC with Chemstation B.04 and am getting area counts of 27 mAU for Epinephrine.

Method is being transferred to another lab and they ran the same exact sample using the same method on the same instrument model and got 27000 mAU area counts! (Not sure of their software)

Only difference I have noticed so far is that their lab ran the samples with a bandwidth of 8 while we used 4 and they used a sampling rate of 5Hz while our lab used 2.5Hz. Cant imagine that would account for their lab getting 1000x higher area counts.

Any ideas?

[Blazer]

The first thing I would do is double check the units used by your lab and the other lab. Perhaps one is set to collect milli-AU and the other is set to collect micro-AU.

[chandled]

The first thing I would do is double check the units used by your lab and the other lab. Perhaps one is set to collect milli-AU and the other is set to collect micro-AU.

Both labs are reporting in "mAU" so I am assuming that means milli AU for both. Shouldnt it be milli as the detector should be seeing milliVolts and converting to milli AU? Is it common to report in micro-
AU?

Both lab's chromatograms are showing approx same heights for the peak but our area reported is 1000 times less.

[Peter Apps]

A peak area has to be signal x time - in this case mAU x time. I suspect that the time bases are different; seconds vs milliseconds or millis vs micros.

Peter

[Blazer]

Both labs are reporting in "mAU" so I am assuming that means milli AU for both. Shouldnt it be milli as the detector should be seeing milliVolts and converting to milli AU? Is it common to report in micro-AU?

Both lab's chromatograms are showing approx same heights for the peak but our area reported is 1000 times less.

No, I don't believe it's common to see area reported in micro-AU but since you've got a difference in area of 1000x, I guessed it would be an issue related to peak area units (Occam's Razor and all that). I would also assume that mAU is milli-AU but it couldn't hurt to double check that with the other lab.

Peter brings up the other side of the simplest possible answer, the unit of time. Again, the fact that you've got 27 vs 27000 leads me to believe it's simply a unit issue. I don't believe the bandwidth or sampling rate would lead to that difference the you see.

[bhuvfe]

Any chance that the integration software used by chemstation is different between the two instruments?

Is this factor 1000 systematic for other samples from that lab?

[chandled]

A peak area has to be signal x time - in this case mAU x time. I suspect that the time bases are different; seconds vs milliseconds or millis vs micros.

Peter

True and good point. Our reports show the units as "mAU*s. So I am guessing that means milliAU time seconds.

The other lab does not have units on the header above the actual area count number. Looking at their run parameters for their detector I see: "Full Scale Range: 1.0Volt(s)", "Attenuation: 1000mAU". So I have no idea if theirs is in seconds or milliseconds or what.

I do agree it has to be something simple that is why it is so maddening.

[chandled]

Any chance that the integration software used by chemstation is different between the two instruments?

Is this factor 1000 systematic for other samples from that lab?

Yes other labs show area counts 1000 times higher in mAU units.

[cody84]

We have the same thing here, different units, but it doesn't matter in the end calculations against standard area right?

[danko]

Chandled,

What is the attenuation on your detector? 1000,000? Units?

Best Regards

[PeterS]

Are you both using the same machine?
May be some connect the detector to a recorder output?

[chandled]

Chandled,

What is the attenuation on your detector? 1000,000? Units?

Best Regards

Attenuation is 1000 mAU