Chromatography Forum

I have a few basic questions about these two spectrometers.

I'm told as the MW of the peptide increases, particularly past 3 kDa, its detection decreases in MALDI,

I understand MW range for LTQ-orbitrap is much greater- Does a similar relationship exist- higher MW, lower detection?

What is the approx relative sensitivity/LOD between the two instruments?

Hi,

1. First assumption:

S/W = K*(1/Mw), S-area of peak, K-coefficient, K=K(A,B,C...), W = weight of analyt per peak (ng per peak etc.).

Basic:
W = Mw*N
A=A(N), A=K*N (A-abundance of analytic signal; K-coefficient, K=const)
If W=const, and if Mw increase => N decrease and A decrease

2. m/z range of Orbitrap vs. TOF - see specification of concrete models

3. sensitivity of Orbitrap vs. TOF - see specification of concrete models

P.S.: amu range of LTQ-Orbitrap etc.: 40-2000amu, 400-4000amu.

No , I think your assumptions are wrong.
Maldi is not limited by Mass range and is the choice for intact peptide work as there is no 4000 M/Z cut off.
Maldi offers the greatest MW range.

What is your application ?
You need to speak to the experts from Thermo for the Orbitap and Bruker for Maldi.

Maldi (Bruker) has greatly improved in the last few years thanks to new lasers and software, in many cases the Orbitrap and a Maldi are complimentary techniques. Speak to both companies , get samples run and only then will you be certain which system (or both) are for you.

I agree, get in touch with Mark Magers from Thermo or maybe Gerry Koncarr. They will tell you anything you need to know.