JASCO Corporation previously shared the advantages of MIX observation screening for Raman analysis on the blog. Today, Erika Taira of JASCO covers another key technology for Raman analysis—water immersion objectives. Erika is in charge of providing solutions using spectroscopic instruments at JASCO. In this interview, she highlights a food analysis study where water immersion objectives from Evident are used to measure and evaluate the differences between different margarine products with a JASCO micro-Raman spectrometer. Read the interview here to learn how water immersion objectives assist in the analysis of margarine and other food products. |
Erika Taira of JASCO. |
Q: What can micro-Raman spectrometers do?
Erika: A wide range of products can be evaluated using the JASCO micro-Raman spectrometers. This includes materials such as resins, films, and batteries to foods and pharmaceuticals. Imaging measurements can be performed to create chemical images that show the distribution of components. Further, a particle size analysis can be carried out to clearly show the differences between products.
In a recent food analysis study, we evaluated the differences between two types of margarines (margarine A and margarine B). Since margarine consists of a water-in-fat emulsion, Raman analysis of the distributions of oil/fat and water facilitates basic research and product development.
Q: How did you use the water immersion objectives with micro-Raman spectrometers in your food analysis study?
Erika: We spread two types of margarine in a thin layer on glass slides and placed a cover glass on top of each slide. The cover glass easily spreads and flattens the margarine sample on a microscopic scale. It also prevents volatilization of the thinly spread sample. While the cover glass enables easy sample preparation, there are cases where it is inconvenient for microscopic observations and Raman measurements. The cover glass can lead to optical interference.
A water immersion objective manufactured by Evident solves this issue. It enables highly sensitive Raman measurements and improves the resolution when performing observations and measurements through a cover glass. Therefore, we mounted the LUMPLFLN60XW water immersion objective from Evident on the JASCO NRS-5500 laser Raman spectrometer to perform imaging measurements of two types of margarine.
Figure 1. Diagram of measurement using a water immersion objective. Image courtesy of JASCO.
Figure 2. JASCO NRS-5500 laser Raman spectrometer and the LUMPLFLN60XW water immersion objective from Evident. Image courtesy of JASCO.
Q: What are the measurement results from the study?
Erika: Figure 3 shows the Raman spectra of the two types of margarine averaged over the entire sample, where the bands associated with water and oils/fats are indicated. Chemical images are shown in Figure 4, which are created using the Raman bands assigned to molecular vibrations of the CH groups in oils and fats and the OH groups in water.
In these images, you can clearly observe the distributions of oils/fats and water. Although differences between margarines A and B can be predicted based only on optical microscopy images, chemical images let you visualize the distribution of the different components. Although water is dispersed in oil in both samples A and B, there is a large difference in the size of the water droplets.
Figure 3. Comparison of average spectra for two types of margarine. Image courtesy of JASCO.
To determine the size distribution of water droplets, we created a histogram using the JASCO Particle Analysis software, and the results are shown in Figure 4. The JASCO Particle Analysis software provides additional analysis functions to the JASCO micro-Raman spectrometer standard software for more detailed analysis of chemical images.
Figure 4 shows that the number of water droplets is approximately 150 in both samples, but the droplets are larger in margarine B, leading to a higher overall water content. Therefore, we can assume that margarine B contains a lower fraction of fat than margarine A and is a lower-calorie product.
Figure 4. Raman analysis results for margarine A (left) and margarine B (right). Top row: optical microscopy images (chemical imaging performed inside yellow frame). Middle row: chemical images (red: oils and fats, green: water). Bottom row: Histogram of water droplet size. Image courtesy of JASCO.
Q: How do you see immersion objectives impacting microscopic Raman measurement in other applications?
Erika: The LUMPLFLN60XW water immersion objective from Evident enabled efficient Raman measurements of margarines, which require special sample preparation. This objective is also effective for suppressing signals from nitrogen, oxygen, and carbon dioxide in atmospheric air. For example, these signals are undesirable when performing Raman measurements of air or gas bubbles inside glass (Japanese patent no. 7397468).
Therefore, combining the JASCO micro-Raman spectrometer and the water immersion objective from Evident expands the application range for Raman analysis. This combination can be applied to research and development of products in a wide range of fields. Examples include foods such as fresh cream and dressings, cosmetics such as sunscreen and hand cream, and industrial materials such as paints and adhesives.
In addition to water immersion objectives, Evident offers a wide variety of other objectives, including long working distance, near-infrared, and darkfield objectives, expanding the range of Raman analysis methods. The team at Evident kindly listened to our requests regarding objective lenses, and we hope to continue to develop our business through collaboration in the future.
Spreading the Range of Raman Analysis Applications
Just like margarine spreads on bread, high-quality immersion objectives spread the range of Raman spectroscopy analyses to a wide variety of food products, cosmetics, and industrial materials. To learn more about our optical components and parts for integration into your microscope-based equipment, visit our OEM Microscope Components page. Find out more about JASCO’s Raman spectometers for material analysis here.
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