Multifaceted Spectrophotometric Analysis of Vitamins and Vitamin-like Substances

Importance of the Topic

Vitamins and vitamin-like compounds are indispensable for human health but cannot all be synthesized internally. Accurate identification and quantification of these micronutrients are critical for food development, quality control, and nutritional research. Integrating multiple spectroscopic techniques enhances reliability and broadens analytical capabilities.

Study Objectives and Overview

This study demonstrates the combined use of UV-Visible spectrophotometry, spectrofluorophotometry, Fourier transform infrared (FTIR) spectroscopy, and Raman microscopy to characterize a range of vitamins (A, B1, B2, B6, C, D, E, K) and vitamin-like substances (p-aminobenzoic acid, anthranilic acid, lipoic acid, rutin). The goal is to showcase each technique’s strengths for qualitative and quantitative analysis.

Methodology and Instrumentation

Samples were prepared by dissolving standards in appropriate solvents (water, ethanol, chloroform, NaOH) and adjusting concentrations to keep UV absorbance below 1 AU or to meet fluorescence sensitivity requirements. Instrumentation and conditions included:

• UV-2600i Plus UV-Visible Spectrophotometer: 200–800 nm range, 1 nm data interval, 1 nm slit width.
• RF-6000 Spectrofluorophotometer: excitation at compound-specific UV/visible peaks, emission scanned 200–650 nm, 1 nm interval.
• IRSpirit-TX FTIR with diamond ATR (QATR-S): 4 cm⁻¹ resolution, 40 scans, DLATGS detector.
• IRTracer-100 Raman Microscope with AIRsight: 532 nm and 785 nm excitation, CCD detector, 10 scans, 5 sec exposure.

Main Results and Discussion

UV-Vis spectra revealed characteristic absorption maxima for each vitamin (e.g., A at 332 nm, B2 at 270/356/449 nm). Fluorescence measurements confirmed the presence of fluorescent chromophores in vitamins A, B2, B6, E, K and some vitamin-like substances; however, certain signals showed instability or baseline drift, likely due to photobleaching or sample fluorescence overlay. FTIR and Raman analyses produced distinct fingerprint bands for all compounds, facilitating library-based identification despite some fluorescence interference in Raman spectra of highly fluorescent samples.

Benefits and Practical Applications

The multi-modal spectroscopic approach enables:

• Rapid, non-destructive qualitative identification in solid and liquid samples.
• Quantitative determination of absorption peaks for routine concentration assays.
• Trace-level detection and confirmation using fluorescence sensitivity.
• Structural verification via ATR-FTIR and Raman without extensive sample preparation.

Future Trends and Potential Applications

Emerging opportunities include coupling spectrophotometric data with chemometric analysis for complex mixtures, expanding spectral libraries for broader compound coverage, refining fluorescence quenching methods to improve Raman signal clarity, and integrating online monitoring in industrial and pharmaceutical processes.

Conclusion

Shimadzu’s range of spectroscopic instruments provides a comprehensive toolkit for profiling vitamins and related compounds. UV-Vis spectroscopy offers reliable quantitative absorption data, fluorescence spectroscopy delivers high sensitivity for trace analysis, and FTIR/Raman techniques afford structural confirmation. Together, these methods support robust workflows in food science, quality assurance, and nutritional research.

Instrumentation Used

• UV-2600i Plus UV-Visible Spectrophotometer
• RF-6000 Spectrofluorophotometer
• IRSpirit-TX FTIR Spectrophotometer with QATR-S diamond ATR
• IRTracer-100 with AIRsight Infrared/Raman Microscope

References

• Analytical Solutions for Food Development
• Difference in Quantifiable Concentration Ranges of UV-Vis Spectrophotometer and Fluorescence Spectrophotometer, Application News No. A615