Introduction

Vibrational circular dichroism spectrometer based on Fourier transform infrared spectrometer (FT-VCD) have been widely used for the molecular structure analysis of chiral compounds. However, since the intensity (DAbs) in the vibrational circular dichroism (VCD) spectrum can be as low as 10^-4 to 10^-5, and the FT-VCD requires a long time for measurement. As a result, it was difficult to measure the VCD spectrum of some biological samples due to the strong infrared absorption band of water. To achieve this, we have newly developed a vibrational circular dichroism spectrometer using a quantum cascade laser (QCL-VCD) as a high-intensity light source. The QCL-VCD (wavenumber range: 1740 to 1500 cm^-1) was combined with the FT-VCD (wavenumber range: 4000 to 850 cm^-1) to realize a system (MultiD-VCD-MIRAI-2020) that achieves both high sensitivity, high speed and a wide measurement range¹. Furthermore, by combining the QCL-VCD with an automated stage and focusing optics, we have realized the micro mapping measurement of small areas of the sample^2-5.

Figure 1. Overview of MultiD-VCD system

Figure 2. Scheme of  MultiD-VCD system

Figure 3. Comparison of light source brightness

Figure 4. Measurement spectra of Glycyl-Leucine

Figure 5. Measurement spectra of a-Pinene

Figure 6. Automatic micro-sampling accessory

Figure 7. IR spot image on the sample

Figure 8. Mapping image of the left hindwing of Anomala albopilosa

Conclusion

A MultiD-VCD system combining QCL-VCD and FT-VCD modes was newly developed. QCL-VCD is capable of measuring strongly absorbing samples such as aqueous solutions. Microscopic mapping measurements can be performed using QCL-VCD at fixed wavenumber.

This work was supported by JSPS KAKENHI (JP17H03044) from Japan Society for the Promotion of Science and JST MIRAI grants (JPMJMI18GC) from Japan Science and Technology Agency.

References

1. H. Sato et al, Anal. Chem. 93 (2021), 2742-2748
2. H. Sato et al, J. Phys. Chem. Lett. 12 (2021), 7733-7737
3. H. Sato et al, Chirality 36 (2024), e23655
4. H. Sato et al, Springer Singapore (2024), ISBN978-981-97-0390-6
5. H. Sato et al, Phys. Chem. Chem. Phys. 24 (2024), 17918-17922

Poster Session at 8^th International Conference on Vibrational Optical Activity (VOA8, August 4 – 8, 2024, Bochum, GERMANY)
Jun Koshoubu¹, Masaru Shimizu¹, Keisuke Watanabe¹, and Hisako Sato²
1JASCO Corporation, Ishikawa 2967-5, Hachioji Tokyo 192-8537, Japan
2 Graduate School of Science and Engineering, Ehime University Matsuyama 790-8577, Japan