Abstract
Accurate quantification of polymer distributions is one of the main challenges in polymer analysis by liquid chromatography. The response of contemporary detectors is typically influenced by compositional features such as molecular weight, chain composition, end groups, and branching. This renders the accurate quantification of complex polymers of which there are no standards available, extremely challenging. Moreover, any (programmed) change in mobile‐phase composition may further limit the applicability of detection techniques. Current methods often rely on refractive index detection, which is not accurate when dealing with complex samples as the refractive‐index increment is often unknown. We review current and emerging detection methods in liquid chromatography with the aim of identifying detectors, which can be applied to the quantitative analysis of complex polymers.
Highlights
One of the most important conditions for a quantitative LC detector’s applicability to complex copolymers is that the detector has a uniform response factor, since many samples are heterogeneous in composition and feature different response factor across the separation
This renders detectors such as the refractive index detector (RID) and other reviewed detectors such as the density detector, magnetic optical rotation based detectors, the acoustic flame detector, and novel mirroring resonator based RID detectors difficult to apply to complex samples as knowledge of possible changes in the response factor over the separation is required for accurate quantification
While requiring some data treatment to correct for nonlinear response factors, recent work using data pointwise linearization of the evaporative light scattering detector (ELSD) signal has shown promising results
Summary
The high molecular weight of most polymers complicates their analysis by MS, and the complexity of the spectrum increases due to the different distributions in combination with multiple charge states [1,2] Detectors such as refractive index detector (RID) and the evaporative light scattering detector (ELSD) are often applied in polymer LC. One would ideally desire not just a universal detector but rather one that shows a universal (absolute) response, meaning that regardless of chemical composition of both the eluting polymer and the eluent, the detector features the same response per mass or concentration of the polymer Such a detector is currently not available that greatly limits quantitative polymer analysis by LC. The recent developments related to LC detectors will be discussed
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