Size Determination of Vitamin B1 by Dynamic Light Scattering

Dynamic light scattering (DLS) is a physics technique used for characterizing the size of particles and molecules in suspension and solution. The technique is based on the measurement of the time-dependent fluctuations in the intensity of the scattered light signals. The particles are responsible for the scattering of the light, while it is the random motion of the particles that produces the fluctuations in that scattering. By measuring the scattering, the particles' velocity can be derived, and from that velocity the hydrodynamic diameter of the particles can be calculated by using the Stokes–Einstein equation.

An important factor for making good DLS measurements is using the right concentration. The concentration of particles must be high enough to produce a good scattering intensity. On the other hand, if the concentration is too high, then multiple scattering may occur, which can produce an erroneous result.

The detection angle can also influence the results: for example, side scattering (90°) is suitable for weakly scattering samples, including small particles and transparent samples; whereas back scattering (175°) is suitable for strongly scattering samples, including large particles, highly concentrated or turbid samples. A distinct function of the Litesizer™ 500 is its automatic measurement-angle selection, which allows the instrument to choose the optimum measurement angle. Selection is based on the sample's transmission, which is measured continuously for all samples. This function is very helpful for users dealing with unknown or unfamiliar samples.

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