In this video, Derek Guenther, Sr. Product Scientist, demonstrates how the SquareOne cuvette holder makes it easy to measure both transmission and reflection from the same liquid sample in parallel. By capturing complementary optical information, you gain clearer insight into how light interacts with complex samples.
Measuring Both Reflection and Transmission Helps You:
- Better interpret scattering samples
Distinguish absorption from scattering in cell cultures, suspensions, and nanoparticle‑based assays. - Monitor formulation and media changes
Detect refractive index shifts caused by solvent composition, concentration, or temperature changes. - Gain confidence in time‑dependent studies
Track reactions, aggregation, or stability changes as optical properties evolve.
Real-World Examples
Biotech Challenge: When Biological Samples Don’t Behave Like Ideal Solutions
In biotech workflows, liquid samples are rarely optically simple. Cell suspensions scatter light. Protein solutions reflect at interfaces. Media composition, concentration, and temperature can subtly change refractive index.
As a result, traditional transmission‑only absorbance measurements often combine multiple optical effects into a single data point, making interpretation harder than it should be.
For applications such as cell growth monitoring, protein characterization, enzyme assays, or formulation development, this can introduce uncertainty:
- Is a signal change due to higher concentration?
- Is absorbance shifting because of chemistry?
- Are subtle sample changes being missed altogether?
When accurate interpretation matters, transmission alone may not be enough.
Aqueous NIR Challenge: When Samples Block Wavelengths of Interest
NIR spectroscopy gives invaluable real-time views into the generation or consumption of chemical species. However, water notoriously absorbs NIR energy above 1700 nm, making transmission difficult if not impossible. But this NIR activity can usually still be seen in reflective mode using the proper optics, which can then be coupled with a sturdy UV-VIS measurement in transmissive mode.
For applications such as drug synthesis, microplastic analysis, or biochemical reactions, a dual-method approach gives deeper visibility:
- Allows monitoring of a color-changing species in the VIS-range, such as an indicator dye, while tracking the formation or degradation of NIR peaks
- Quantifies protein concentration in the UV-range while correlating to the complementary NIR activities
When the full spectral range matters, using a clever arrangement allows visibility into what was otherwise hidden.
Fluorescence Challenge: When Excitation LEDs Can’t Interfere with Absorbance
Many fluorescent compounds also have interesting and useful broadband absorbance activities, but traditional 90° fluorescence uses 2-of-the-3 available ports needed for a broadband signal. By using a fluorescence probe on the 90° port for both excitation and emission, the 180° ports can be devoted to broadband absorbance. For applications looking at chlorophyll levels in plant extracts, or quenched activities of porphyrins, this approach opens the door to deeper analysis:
- Tracks overall concentration and composition of plant extracts via absorbance while giving real-time fluorescence profiles
- Shows extent of porphyrin quenching while ensuring sample is excited at absorbance maximum
When your compound has multiple optical activities, a dual-method approach combines two studies into one setup.