While the concentration detector shows a stable baseline, that is, it is balanced to the solvent itself, an increased LS baseline level (also referred to as high background) and a noisy LS signal are reported when a molar mass sensitive LS detector is connected for the first time to an existing system or when new columns are installed. On the other hand, columns could unintentionally be a source of contamination. They are able to detect large analytes at concentrations that are below the detection limit of concentration detectors, such as RI or UV, and therefore using them for analysis is very challenging because they require very clean systems.Īn advantage of GPC/SEC-LS compared to batch LS experiments is that the columns can act as a huge filter so that extensive solvent filtration (typical for batch application) can be avoided. LS detectors respond very sensitively to high molar masses and large sizes and particles, not only from the sample of interest, but also from any contamination in the system. What are the Challenges When Working with Light Scattering Detectors? In order to gain precise, accurate, and reliable results, impurities that interfere with the LS detector need to be reduced to a minimum. To obtain the desired results, LS detectors need to be combined with at least one concentration detector, such as a differential refractive index (RI) detector or a UV detector. This sample-solvent parameter is addressed as the refractive index increment, dn/dc. The sample itself also plays an important role: the higher the polarizability of the sample (compared to the solvent), the higher the signal intensity. The higher the molar mass and the concentration, the higher the measured signal intensities. Their signal response depends on both the concentration and the molar mass. Light scattering detectors are molar mass sensitive detectors. These detectors should never be confused with evaporative light scattering detectors (ELSDs) (2), which measure scattered light of analyte droplets after mobile phase evaporation. The light scattering (LS) detector models differ mainly in the position where the scattered light is measured and in the number of simultaneously acquired signals. This instalment of Tips & Tricks discusses column issues when working with light scattering detectors.ĭetectors to measure the intensity of scattered light in solution are very popular additions to gel permeation chromatography/size-exclusion chromatography (GPC/SEC) instruments because they add true value (1). However, the complexity of the system also increases. The addition of a light scattering detector dramatically increases the capabilities of gel permeation chromatography/size-exclusion chromatography (GPC/SEC) analysis.

Dndc of pmma in dmf