Using a MALS instrument to measure unfractionated samples, often referred to as batch mode analysis, can be an invaluable characterization method. This type of measurement provides the weight-average molar mass, the z-average RMS radius, and the second virial coefficient (A2) of a sample and its unfractionated components. You may not be able to distinguish between individual constituents in these measurements; however, batch mode can be a quick, convenient complement to SEC-MALS or FFF-MALS.
When to use batch measurements
Batch measurements are used in a variety of instances, including when:
The microCurvette accessory
Batch measurements can be performed by injecting the sample into a DAWN® or miniDAWN® flow cell. If you own a DAWN, batch measurements may also be carried out with a microCuvette™ (p/n WMCW). The microCuvette can be purchased as an accessory kit that includes everything you need to run batch experiments. It comes with a quartz cuvette and a cuvette holder, which is easily installed in place of the flow cell manifold, as shown below.
The microCuvette uses detectors 7, 9, 11, and 13 in the DAWN and detectors 3-6 in the DAWN 8 to make angular measurements of light scattering. (ASTRA automatically enables the correct detectors when you select the microCuvette as the sample cell). This allows for RMS radius determination from 10 to 50 nm (up to 150 nm with shape-specific models) as well as molar mass determination between 200 Da to 10 MDa. It is also compatible with the WyattQELS™ module when the DLS fiber is installed at the 90° detector angle, enabling simultaneous acquisition of MALS and DLS data, and expanding the size range to Rh = 0.5 nm to 1 µm.
The microCuvette has a number of advantages over the flow cell and can be the perfect tool when:
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