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hplc detector....which is the best?
Posted: Sat Nov 15, 2008 9:53 am
by che313
hi dears,
variable wave, multiaple wave, diode array or refractive index
which one of them is suitable for narcotics analysis: Heroin, cocaine, amphetamine, mdma, morphine, cannabis, etc??
Posted: Sat Nov 15, 2008 2:51 pm
by JGK
Depends on how much you have to spend.
Personally I would rank them as follows (in the order of usage)
Variable/multiple wavelength UV/Vis
Diode Array UV
Evaporative Light Scattering
Fluorescence
Refractive Index.
Analysis method for "drugs of abuse" use UV and Diode array detectors (if you haven't a MS unit handy)
Posted: Sat Nov 15, 2008 11:28 pm
by che313
u mean the cost??
I want the performance and sensitivity.
thank you for your reply
Posted: Sun Nov 16, 2008 11:04 am
by AA
If you want want the performance and sensitivity for those compounds you want to use MS/MS. VWD and MWD may (may, not always, lots of previous threads on that) give you slightly better sensitivity tham PDA but no spectral information.
Posted: Sun Nov 16, 2008 4:34 pm
by che313
thank you AA
looking for sensitivity but not looking for MS/MS scince we will order LC/MS/MS also.
but know as we already have an isocratic pump, eclipse sdx c18 column & manual injector, I think we need a detector and may be deagsser and column compartment to get a HPLC system.
I read some application notes from agilent and I found that a set of two detectors will suit our requiremnets; varaible wavelength & evaporative light scattering detectors.
My questions are: is the deqasser part sufficient or optional?
also is the column compartment sufficient or optional?
and finally can we upgrade the isocratic pump to a binary pump?
Posted: Sun Nov 16, 2008 4:51 pm
by JGK
the list I gave you was in terms of those I have used most often not in terms of cost.
If you are looking to build a system you should aim for
A binary pump ( having an isocratic pump only severely limits the number of methods you can run).
Degasser unit
Column oven
Injector system (automated or manual)
Detector UV and or ELSD (for the ELSD you will need a good nitrogen supplyas it can use 1 cylinder/day with some methods)
Posted: Tue Nov 18, 2008 3:17 pm
by wulffniedner
To make things clear, I think it might be worth to point out that from an optics perspective there is no difference between an MWD and a DAD. MWDs are basically DADs without spectra acquisition. VWDs on the other hand select the wavelength before the light enters the flow cell. VWDs are typically much better in sensitivity.
Posted: Fri Nov 21, 2008 5:35 am
by detox
che313
If you have a Agilent isocratic pump this can not be upgraded to a binary pump but it can be upgraded to a quaternary pump (add a multichannel gradient valve MCGV). There is a connection already on the isocratic pump mainboard to connect the MCGV. Once the pump is powered up the board will recognize that the valve was added and you now have a quaternary pump.
If you stay with the isocratic pump you will not need a degasser, a Agilent quaternary pump must have a degasser since it utilizes low pressure mixing, a Agilent binary pump utilizes high pressure mixing so a degasser is not necessary.
I would check app. notes for the drugs that you are analyzing. If the methods are utilizing column heaters then you may need one in order to achieve the same resolution that the app. notes are getting. If the methods are all at ambient temps. then why get a column heater?
Hope that helps.