1
|
I have recently set up the eretic sample concentration measurement experiment experiment on our AvanceIII instrument. It seems to work well but the accuracy of the technique depends on the standard sample used to calibrate, I used the Bruker 48.5 mM triphenylphosphate standard since it would be good for 1H, 13C and 31P and its concentration is known fairly precisely however I have been advised that these standards from bruker use thinner walled tubes than most of my users purchase and that therefore they have a different volume and this will lead to errors to concentration determination. Does anyone know of a standard good for the eretic technique. |
|
1
|
Matthew, the 31P standard is in a tube with regular wall thickness. Wilmad type 535 or 528 or equivalent are used. These tubes and all precision tubes have reasonably well defined outer and inner diameters with tolerances. One-way or other economy tubes typically have no specification for inner diameter or tolerances thereof. This can lead to significant errors in quantitation. TMP is certainly a good standard if you want to include 31P. For 1H and 13C Dimethylsulfone has been proposed. Clemens |
|
0
|
Quantification is easy if you don't mind about accuracy but much harder if you do. Clemens' comment about tube diameters is a big potential source of errors, depending on the specification of the tubes that you use. Other things to watch out for: relaxation time of standard and sample, offset from central frequency, purity of standards, integration method, signal to noise, inclusion or not of 13C satellites, baseline correction, phasing, probe tuning, probably a lot more... John |
