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Tint Plate Upgrade Provides Clearer Analysis Images

by biopharma-admin in BTL News Cat 1, BTL Right Sidebar Content

April 2014

A first order red filter upgrade is available for the BTL Lyostat3 and Lyostat4LED systems.

Lyostat Freeze Drying Microscopy

Analysis using Lyostat freeze drying microscopy (FDM) enables a range of important freeze drying characteristics to be identified, including collapse temperature (Tc). FDM works by freeze drying a sample in real time under a microscope so that structural events can be observed in relation to specific temperature and pressure parameters.

FDM is a visual analysis and therefore any improvements that can provide clearer images will enable easier, more precise analysis.

Fig 3. Analyser collar and tint plate assembly fitted to imaging station

Fig 1. Analyser collar and tint plate assembly fitted to imaging station

Plane Polarised Light

The first order red filter upgrade consists of a tint plate assembly containing both a Birefringent light retardation plate as well as a light polarising “analyser” lens, which are used in conjunction with the polarising lenses already included with the Lyostat systems.

As plane polarised light passes through the first order red filter, all wavelengths experience a degree of polarisation which alters the orientation of the light.  The tint plate is designed such that green light in the 550nm wavelength region is retarded by exactly one wavelength and remains in a perpendicular orientation with respect to the analyser lens and is, therefore, absorbed. Other wavelengths in the blue and red range pass through the analyser lens to the camera, resulting in a Magenta-red colour. Birefringent samples such as crystalline structures commonly observed in frozen formulations for freeze-drying can also affect the orientation of light passing through and shifts the wavelengths of light able to traverse the analyser lens. This results in a vivid display of different hues, typically yellow and blue colour, depending on the orientation of the crystal structures at various locations within the sample (Fig 2).

Fig 1. Images showing the appearance of a 4% NaCl solution under normal white light (left; polarised light (middle); and polarised light including a red filter (right)

Fig 2. Images showing the appearance of a 4% NaCl solution under normal white light (left; polarised light (middle); and polarised light including a red filter (right)

Tint Plate Upgrade

The tint plate assembly, when used in conjunction with the freeze-drying microscope, provides qualitative information about the orientation of crystal structures within the samples analyses. It also enhances the contrast between crystalline structures, which enables easier identification of changes to the crystalline nature of the sample being analyzed and makes it easier to identify phenomena such as eutectic melting. Furthermore the artificial hue imparted to the samples enhances the contrast between collapsing material and good dried structure making it easier to identify the onset of collapse temperature of the amorphous phase (Fig 3).

Fig 2. Images of a 4% sucrose solution collapsing under polarized light including red filter (left) and normal white light (right).

Fig 3. Images of a 4% sucrose solution collapsing under polarized light including red filter (left) and normal white light (right).

The tint plate assembly is retro-fitted using a purpose build analyzer collar assembly and  is suitable for a wide range of commercially available imaging stations.

Upgrades and After Sales Support

Lyostat freeze drying microscopes are used day to day in BTL’s consultancy work. All upgrade, qualification and operator training is provided  by research scientists who can advise on interpretation and application of results. If you are upgrading a system on-site we recommend you take advantage of the expertise at hand and schedule a refresher course. Training can be carried out using real product if required, providing you with instant relevant results.

Other upgrades may be available, depending on the configuration of your existing system. To discuss your requirements contact Nektaria: nservi@biopharma.co.uk.

Product Characterization Using Freeze Drying Microscopy: A Case Study

Read a case study about how characterization using freeze drying microscopy helped one client>>

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