Sasić Slobodan, Clark Donald A, Mitchell John C, Snowden Martin J
Pfizer Global Research and Development, Ramsgate Road, Sandwich, UK.
Analyst. 2005 Nov;130(11):1530-6. doi: 10.1039/b506523b. Epub 2005 Sep 23.
This paper describes the use of principal component analysis (PCA) to de-noise Raman spectra and considerably shorten data acquisition time in Raman mapping experiments. A solid dosage pharmaceutical material (bead) is mapped by a Raman line-mapping system. The mapping acquisition time was varied from 30 s (usually employed in practice) to only 3 s. Apparently excessive noise in the maps measured for 3 s is removed by PCA and the maps of all three components of the bead are then binarized and compared. It is found that spatial difference is negligible despite the remarkably different acquisition times employed. The spectra acquired for 3 s and reconstructed via PCA are found to largely overlap with the spectra acquired for 30 s. The signal to noise ratio of the Raman mapping spectra does not obey the expected root t dependence, thereby preventing straightforward estimation of the shortest usable acquisition time (which is to a lesser extent also a function of the binarization threshold). The results reveal that Raman microscopy can be considered a fast method for mapping some materials, in contrast to the established opinion that it is an inherently slow technique.
本文描述了如何使用主成分分析（PCA）对拉曼光谱进行去噪，并在拉曼映射实验中大幅缩短数据采集时间。通过拉曼线映射系统对一种固体剂型药物材料（微珠）进行映射。映射采集时间从30秒（实际中通常采用的时间）变化到仅3秒。通过PCA去除了在3秒测量的映射中明显过多的噪声，然后对微珠所有三个成分的映射进行二值化并比较。结果发现，尽管采用的采集时间显著不同，但空间差异可以忽略不计。发现通过PCA重建的3秒采集的光谱与30秒采集的光谱在很大程度上重叠。拉曼映射光谱的信噪比不遵循预期的根t依赖性，从而无法直接估计最短可用采集时间（在较小程度上，这也是二值化阈值的函数）。结果表明，与认为拉曼显微镜本质上是一种缓慢技术的既定观点相反，拉曼显微镜可被视为一种用于某些材料映射的快速方法。
