导数法在中红外光谱教学中的应用

Application of derivative method in teaching of MIR spectroscopy

以医用白凡士林为例,通过导数法对中红外光谱数据进行处理。采用一维中红外光谱,结合一阶导数MIR光谱、二阶导数MIR光谱、三阶导数MIR光谱和四阶导数MIR光谱,对医用白凡士林进行了结构研究。结果表明,医用白凡士林分子主要存在CH_(3)不对称伸缩振动模式(ν_(asCH_(3)-医用白凡士林))、CH_(2)不对称伸缩振动模式(ν_(asCH_(2)-医用白凡士林))、CH_(2)对称伸缩振动模式(ν_(sCH_(2)-医用白凡士林))、CH_(3)不对称变角振动模式(δ_(asCH_(3)-医用白凡士林))、CH_(3)对称变角振动模式(δ_(sCH_(3)-医用白凡士林))、CH_(2)面内摇摆振动模式(ρ_(CH_(2)-医用白凡士林))等。二阶导数MIR光谱的谱图分辨能力要优于相应的一维MIR光谱和四阶导数MIR光谱。选择适宜的平滑点数,可有效提高导数光谱的分辨能力,为拓宽中红外光谱的应用领域提供理论支撑和实践应用借鉴。

Taking medical white vaseline as an example,the MIR spectrum data were processed by derivative method.The structure of medical white vaseline was studied by using one-dimensional MIR spectrum combined with first derivative MIR spectrum,second derivative MIR spectrum,third derivative MIR spectrum and fourth derivative MIR spectrum.The results show that the medical white vaseline molecule mainly exists CH_(3)asymmetric stretching vibration mode(ν_(asCH_(3)-medicalwhitevaseline)),CH_(2)asymmetric telescopic vibration mode(νasCH_(2)-medicalwhitevaseline),CH_(2)symmetric telescopic vibration mode(ν_(sCH_(2)-medicalwhitevaseline)),CH_(3)asymmetric variable angle vibration mode(δ_(asCH_(3)-medicalwhitevaseline)),CH_(3)symmetrical variable angle vibrationmode(δ_(sCH_(3)-medicalwhitevaseline)),CH_(2)in-planerockingvibrationmode(ρ_(CH_(2)-medicalwhitevaseline)).The spectral resolution of the second derivative MIR spectrum is better than that of the corresponding one-dimensional MIR spectrum and the fourth derivative MIR spectrum.Choosing appropriate smoothing points can effectively improve the resolution ability of derivative spectrum,and provide theoretical support and practical application reference for expanding the application field of MIR spectrum.