On June 23rd, 2020 we held our first virtual Morphologi 4-ID user meeting. which aimed to highlight the different ways in which the instrument is being used in various application spaces and in conjunction with other technologies.
The first, by Dr. Evan White from the New Materials Institute at the University of Georgia, discussed the impact of microplastics on the environment with a specific analysis of the composition and size distributions of microplastics ingested by sea turtles.
The second, by Dr. Kevin Dahl with KBI Biopharma, highlighted their particle investigation workflow in biotherapeutics using automated Raman microspectroscopy and other tools.
Several questions regarding the instrument and its functionality were asked by our users during the meeting, and some questions were also submitted during the talks. As our conversation was cut short by time constraints, I share here the meeting questions and associated answers.
Q: What is the spatial resolution vis-à-vis optical image and the Raman scattering spot size
The instrument has a particle size range of 0.5 – 1300µm overall, with a spatial resolution of 0.5µm when the 50X microscope objective is used. The Raman spot is 2µm; depending on the strength of the associated Raman scattering particles as small as 1µm can be tested.
Q: Is the analysis of liquid samples possible? What to consider regarding this?
Yes, the analysis of liquid samples is possible. Several accessories are available to present the liquid sample to the instrument. The wet cell can be used for morphological analysis of ~3 to 6mL of a suspension, while the thin path cell is best suited for Raman analysis of subvisible particulates in therapeutics. Suspensions can also be tested in a microscope slide / coverslip configuration.
Q: Which type of samples are likely to show fluorescence background interfering with the Raman scattered signal with the 785 nm laser?
Fluorescence background in the Raman signal is typically mitigated by the choice of a longer excitation wavelength such as 785nm laser used in the Morphologi 4-ID system. When this is not the case, one can experiment adjusting the laser power (1-100%) and the exposure time such that the fluorescence effects are minimized.
Q: Can PM 2.5 or 10 as in air particulate matter (dispersed collection can be done using special cascade impactors) classified using the Morphologi 4-ID?
Particle sizes larger than 0.5µm and less than 2.5µm (PM 2.5) and 10µm (PM10) in size can easily be visualized with the Morphology 4 using the 50X microscope objective. Determining the concentrations of particulates of these sizes in air however is going to be largely related to the method of collection and presentation of the samples to the instrument. A particle counter is best suited for this type of analysis.
Q: How are filters different than classes in the Morphologi 4 software?
The difference is simply in excluding or including particles from the imaged particles database in a certain record. Filters are used to remove unwanted particles (touching particles, pixelation, particulates with limited pixels for which a true shape cannot be defined) from the analysis. Classes are used to group particles of various size, shape, intensity and/or chemical correlation, such that samples can easily be classified based on certain parameters of interest.
We loved learning how our technology advances research and discovery. Stay tuned for more MOR4ID related content.