Peak area

[pankajcops]

Hi,
In dionex HPLC the peak area comes into mAU*min. The area in that case comes into two digits.So we multiply it by 60000.Can any body tell me why we do so and if we are doing that the area will be in mAU or µAU?

[Bruce Hamilton]

Because you like large numbers?. I assume uAU and seconds are more
relevant to your peak width and height.

If I performed the maths correctly ( an unusual and rare event ), then
multiplying by 1000 will convert mAU to uAU, and multiplying by 60 will convert the time component from minutes to seconds.

60,000 uAU*sec = 1 mAU*min

Bruce Hamilton

[pankajcops]

Because you like large numbers?. I assume uAU and seconds are more
relevant to your peak width and height.

If I performed the maths correctly ( an unusual and rare event ), then
multiplying by 1000 will convert mAU to uAU, and multiplying by 60 will convert the time component from minutes to seconds.

60,000 uAU*sec = 1 mAU*min

Bruce Hamilton

Thank you Bruce.I want to know that in Dionex we get result in µAU and in waters we get in Au when we inject the same injection but the area is approximately same. Why it happens , whether this may due to the difeerent software or anything ele

[unmgvar]

pankajcops

before you were talking of peak area and i am assuming that now you are talking of the signal response.
Dionex signal is in mAu and that of waters is AU, just because.
i personnally find it easier to look at a signal when it is displayed in mAU, like most of us prefer to see big area numbers without decimals.
go figure out why waters have not changed the settings on that yet? anyway if you so desire (but i do not recommend it) you can change the signal scale for your dionex detector to be AU as well.
it is all a question of units like 1 meter is 100 centimeters. they are still the same physical value.

[DR]

If you're doing anything quantitative, whatever the units are - they should all cancel out at some point in the calculations anyway (so I don't worry about them).

[Mark Tracy]

I suspect the reason for doing the multiplication is because the report shows only two significant figures, and the chemists want to see more. It would make more sense to change the format of the report to report more decimal places. Also, if you want to continue using the factor of 60000, the report header should be changed to show the altered units.

The Dionex software may well be locked so that only authorized persons may modify the reports (in any cGMP/ISO regulated lab this should be the case). If so, ask your supervisor.

Finally, please don't take the rounded off numbers and multiply them, that only gives an illusion of better precision. Instead, you should always multiply before rounding off for reporting.