A:
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SEC
separations are often calibrated using pure, narrow molecular weight
standards of the sample components that are being analyzed.
Prepare a calibration plots of various molecular weights of the sample
component as a function of
elution volume/time.
Make sure that the SEC pump delivery is constant . The apparent
molecular weight of the sample can vary significantly with a small flow
fluctuation, since the relationship between Molar mass and elution
volume is logarithmic
Because the actual component is not always
available, Various standards can be used
instead. Narrow polystyrene standards are commonly used for
calibrations that run in organic solvents. Because SEC
separations are based on Molecular size (weight) the
polystyrene calibration plots allow to estimate the molecular weight of
the sample, by interpolation.
There are various methods to calibrate the detectors used and find the
plot's best polynomial fit. These methods are well covered by the
software used to acquire the data. For example, WinGPC
Unity provides a wide selection of calibration methods computed
with proprietary calibration fit routines that yield high accuracy and
precision:
• Calibration with
narrow standards
• Universal calibration with Mark-Houwink constants
• Broad standards calibration and cumulative match calibration are
provided with step-by-step guides that assure integrity of process
• More calibration variety with software modules
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