Chromatography Forum

Hi everyone,

First off all i would like to thank everyone who responds for my queries.

My questions are:

(1)In the HPLC method-DAD signal what is the refrence point related to?
(2) What is the bandwidth (for eg 10) is related ?

Thanks.

The reference point can mean two things, and both can apply at the same time. One is some wavelength far off the absorption maximum that the DAD uses to compensate for refractive index or minor lamp variation. Using this may or may not improve the quality of the chromatogram; try it both ways. The second meaning is a spectrum taken at the baseline of a peak and subtracted from the spectrum across the rest of the peak; this gives you the spectrum of the substance corrected for local background effects.

The bandwidth is how many diodes are averaged together to produce the signal at the center. A bandwidth of 10 and a wavelength of 254 means that all the diodes between 249 and 259 are averaged to represent the signal at 254.

Thank you so much!

I understood.

Thanks.

on the method that I'm using there is verbage that states:
UV Detector slit width = 4 nm
peak width = 0.05 min.
sampling interval = 0.320 secs

?Exactly what does that verbiage mean? especially the sampling interval?

Thank you.

The sampling interval is the reciprocal of the data collection rate. The filter constant is calculated (internally?) from the peak width; the equation varies from vendor to vendor. The slit is a mechanical device for setting the bandwidth on single-wavelength (or fast-scan) detectors. The slit is usually fixed, but sometimes is adjustable.

OK, thank you