Quantitative determination of n-heptane and n-octane using terahertz time-domain spectroscopy with chemometrics methods

Abstract

This paper introduces the terahertz time-domain spectroscopy (THz-TDS) used for the quantitative detection of n-heptane volume ratios in 41 n-heptane and n-octane mixtures with the concentration range of 0-100% at the intervals of 2.5%. Among 41 samples, 33 were used for calibration and the remaining 8 for validation. Models of chemometrics methods, including partial least squares (PLS) and back propagation-artificial neural network (BP-ANN), were built between the THz-TDS and the n-heptane percentage. To evaluate the quality of the built models, we calculated the correlation coefficient (R) and root-mean-square errors (RMSE) of calibration and validation models. R and RMSE of two methods were close to 1 and 0 within acceptable levels, respectively, demonstrating that the combination of THz-TDS and chemometrics methods is a potential and promising tool for further quantitative detection of n-alkanes.

Keywords

terahertz time-domain spectroscopy (THz-TDS) / n-heptane / n-octane / partial least squares (PLS) / back propagation-artificial neural network (BP-ANN)

References

[1] Yamaguchi M, Serafin S V, Morton T H, Chronister E L. Infrared absorption studies of n-heptane under high pressure. Journal of Physical Chemistry B, 2003, 107(12): 2815–2821

[2] Brunel L C, Dows D A. Raman spectra of n-alkane crystals: lattice vibration of n-hexane, n-heptane and n-octane. Spectrochimica Acta Part A: Molecular Spectroscopy, 1974, 30(4): 929–940

[3] Snyder R G, Kim Y. Conformation and low-frequency isotropic Raman spectra of the liquid n-alkanes C₄-C₉. Journal of Physical Chemistry, 1991, 95(2): 602–610

[4] Cameron D G, Hsi S C, Umemura J, Mantsch H H. Solvent induced frequency shifts of the C-H stretching bands of n-octane. A Fourier transform infrared study. Canadian Journal of Chemistry, 1981, 59(9): 1357–1360

[5] Zhao H, Zhao K, Bao R M. Fuel property determination of biodiesel-diesel blends by terahertz spectrum, Journal of Infrared, Millimeter, and Terahertz Waves, 2012, 33(5): 522–528

[6] Dragoman D, Dragoman M. Terahertz fields and applications. Progress in Quantum Electronics, 2004, 28(1): 1–66

[7] Watanabe Y, Kawase K, Ikari T, Ito H, Ishikaw Y, Minamide H.Component analysis of chemical mixtures using terahertz spectroscopic imaging. Optics Communications, 2004, 234(1–6): 125–129

[8] Tian L, Zhou Q L, Jin B, Zhao K, Zhao S Q, Shi Y L, Zhang C L. Optical property and spectroscopy studies on the selected lubricating oil in the terahertz range. Science in China Series G: Physics, Mechanics and Astronomy, 2009, 52(12): 1938–1943

[9] Zhao H, Zhao K, Tian L, Zhao S Q, Zhou Q L, Shi Y L, Zhao D M, Zhang C L. Spectrum features of commercial derv fuel oils in terahertz region. Science China Physics, Mechanics & Astronomy, 2012, 55(2): 195–198

[10] Bao R M, Wu S X, Zhao K, Zheng L J, Xu C H. Applying terahertz time-domain spectroscopy to probe the evolution of kerogen in close pyrolysis systems. Science China Physics, Mechanics & Astronomy, 2013, 56(8): 1603–1605

[11] Wold S, Sjöström M, Eriksson L. PLS-regression: a basic tool of chemometrics. Chemometrics and Intelligent Laboratory Systems, 2001, 58(2): 109–130

[12] Cai C B, Yang H W, Wang B, Tao Y Y, Wen M Q, Xu L. Using near-infrared process analysis to study gas–solid adsorption process as well as its data treatment based on artificial neural network and partial least squares. Vibrational Spectroscopy, 2011, 56(2): 202–209

[13] Laib J P, Mittleman D M. Temperature-dependent terahertz spectroscopy of liquid n-alkanes. Journal of Infrared, Millimeter, and Terahertz Waves, 2010, 31(9): 1015–1021

[14] Hua Y F, Zhang H J. Qualitative and quantitative detection of pesticides with terahertz time-domain spectroscopy. IEEE Transactions on Microwave Theory and Techniques, 2010, 58(7): 2064–2070

[15] Hua Y F, Zhang H J, Zhou H L. Quantitative determination of cyfluthrin in n-hexane by terahertz time-domain spectroscopy with chemometrics methods. IEEE Transactions on Instrumentation and Measurement, 2010, 59(5): 1414–1423

[16] Wu H Q, Heilweil E J, Hussain A S, Khan M A. Process analytical technology (PAT): quantification approaches in terahertz spectroscopy for pharmaceutical application. Journal of Pharmaceutical Sciences, 2008, 97(2): 970–984

Acknowledgements

This work was supported by the Specially Funded Program on National Key Scientific Instruments and Equipment Development (Grant No. 2012YQ140005), the Science Foundation of the China University of Petroleum (Beijing) (Grant Nos. QZDX-2010-01, KYJJ2012-06-27 and JCXK-2011-03), and the Open Project Program of Key Laboratory of Functional Crystals and Laser Technology, TIPC, CAS (Grant No. JTJG201201).

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg