Biotage Isolera Four, Руководство пользователя

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411829-L, Troubleshooting April 2012 Page 6-4
6
6.6 Gradient Problems
Problem Solutions
Low composition
gradient is not correct. When generating solvent mixtures where the composition contains less than 10%
of one solvent:
1. Ensure that the solvent with the lowest percentage is pumped first, i.e. is
mounted on a solvent inlet with a lower number than the solvent with the
highest percentage. Use for example inlet S1 for the solvent with the lowest
percentage and S2 for the other one.
2. If the problem persists, premix the solvent using the desired final % strong
solvent in the weak solvent and use this as solvent B. Program the gradient
from 0–100% B using the pre-mixed solvent B. See “Create, Open, and Edit
Methods” on page 4-2.
The baseline drift is
different from the
programmed gradient. Two factors contribute to altering the gradient as observed by the detector on the
output side of the cartridge:
1. As it takes at least 1 CV for the solvent to pass through the cartridge and
reach the detector, the initial front of the gradient will always be delayed by at
least 1 CV compared to the programmed gradient. A longer gradient delay
may be due to interactions with the silica, where strong solvent is being
selectively retained on the cartridge.
2. The gradient as observed by the detector will at times decline and plateau
before the programmed gradient does. This is due to the detector reaching
saturation for the wavelengths absorbed by the strong solvent. Any increase
in the concentration of strong solvent will not be registered as no light is
penetrating the solvent at those particular wavelengths.
If using a system with a Spektra license installed, try performing the run with the
Baseline Correction option turned on.
Extremely jagged
peaks at absorption
levels below 50 mAU. As the system only reports absorption in whole numbers (in mAU), a peak
recorded at a low level will suffer from quantification noise. This problem may be
solved by increasing the path length of the UV cell. This increases the sensitivity
at the cost of a lower saturation concentration. For more information, please
contact 1-Point Support.