Chromatography Forum

THANKS FOR REDING THIS FELLOWS

I WOULD LIKE TO GET ANY OPINION ABOUT . WHAT IS THE APROPRIATE NUMBRE OF DIODES THAT A PHOTODIODE ARRAY DETECTOR SHOULD HAVE.

FOR EXAMPLE PERKIN ELMER HAVE ONLY 512 DIODES AND THE REST OF MODELS IN OTHER MARKS HAVE 1024 DIODES. WHATS THE DEAL WITH THESE. I READ THAR THE RESOLUTION COULD BE THE REASON.

RESOLUTION = (WL 1 - WL 2) / number of diodes

For example if I calculate this for PErkin Elmer (Flexar)

Resolution PE = (700 nm - 190 nm )/512 diodes = 0.996 nm/diode

(reported as 1,09 nm /diode by Perkin Elmer)

For the others I have, for example:

Resolution OT = (900 nm -190 nm) /1024 diodes = 0,693 nm / diodes

Aparently the second one is the best BUT IN BOTH OF THEM the wavelength accuracy is 1 nm. So no matter if the resolution is 0,693 nm / diode because the accuracy exactitud is always 1 nm.

IS IT RIGHT WHAT I THINK???? PLEASE I NEED SOME ADVICE ... I AM LOOKING FOR AN ANSWER OR AT LEAST AN OPINION.

THANKS SOOOO MUCH FOR YOUR HELP

For LC detection, we are usually quite happy to sacrifice spectral resolution at the altar of low cell volume and good signal/noise ratio. In practice, the signals from adjacent diodes are often combined (via the "bandpass" setting") anyway, so the number of diodes is not that important. For spectrophotometry, the opposite is true: spectral resolution is *very* important and so the more diodes, the better.

Thank you TOM

It gives me some ideas. As I realized, the wavelength acuracy of 1 nm take me to evaluate de "bandpass " , as I thoght. So these fact makes irrelevant the number of Diodes, as you said, at least in this case where the resolution is the most important.

Again, I appreciate your advice , have I nice day, I hope your answers for my next questions, if you can. It is a great place to take advice.