Hoffmann Uwe, Pfeifer Frank, Hsuing Chang, Siesler Heinz W
nir-tools, Essen, Germany.
Department of Physical Chemistry, University of Duisburg-Essen, Essen, Germany.
Appl Spectrosc. 2016 May;70(5):852-60. doi: 10.1177/0003702816638284.
The aim of this contribution is to demonstrate the transfer of spectra that have been measured on two different laboratory Fourier transform near-infrared (FT-NIR) spectrometers to the format of a handheld instrument by measuring only a few samples with both spectrometer types. Thus, despite the extreme differences in spectral range and resolution, spectral data sets that have been collected and quantitative as well as qualitative calibrations that have been developed thereof, respectively, over a long period on a laboratory instrument can be conveniently transferred to the handheld system. Thus, the necessity to prepare completely new calibration samples and the effort required to develop calibration models when changing hardware platforms is minimized. The enabling procedure is based on piecewise direct standardization (PDS) and will be described for the data sets of a quantitative and a qualitative application case study. For this purpose the spectra measured on the FT-NIR laboratory spectrometers were used as "master" data and transferred to the "target" format of the handheld instrument. The quantitative test study refers to transmission spectra of three-component liquid solvent mixtures whereas the qualitative application example encompasses diffuse reflection spectra of six different current polymers. To prove the performance of the transfer procedure for quantitative applications, partial least squares (PLS-1) calibrations were developed for the individual components of the solvent mixtures with spectra transferred from the master to the target instrument and the cross-validation parameters were compared with the corresponding parameters obtained for spectra measured on the master and target instruments, respectively. To test the retention of the discrimination ability of the transferred polymer spectra sets principal component analyses (PCAs) were applied exemplarily for three of the six investigated polymers and their identification was demonstrated by Mahalanobis distance plots for all polymers.
本论文的目的是通过使用两种不同类型的光谱仪仅测量少量样品，来展示如何将在两台不同的实验室傅里叶变换近红外（FT-NIR）光谱仪上测得的光谱转换为手持式仪器的格式。因此，尽管光谱范围和分辨率存在极大差异，但在实验室仪器上长期收集的光谱数据集以及据此开发的定量和定性校准，都可以方便地转换到手持式系统中。这样，在更换硬件平台时，制备全新校准样品的必要性以及开发校准模型所需的工作量都被最小化。实现该转换的过程基于分段直接标准化（PDS），将针对定量和定性应用案例研究的数据集进行描述。为此，将在FT-NIR实验室光谱仪上测得的光谱用作“主”数据，并转换为手持式仪器的“目标”格式。定量测试研究涉及三元液体溶剂混合物的透射光谱，而定性应用示例则包括六种不同商用聚合物的漫反射光谱。为了证明定量应用中转换过程的性能，针对溶剂混合物的各个成分，利用从主仪器转移到目标仪器的光谱建立了偏最小二乘法（PLS-1）校准，并将交叉验证参数分别与在主仪器和目标仪器上测得的光谱所获得的相应参数进行比较。为了测试转移后的聚合物光谱集鉴别能力的保留情况，对六种被研究聚合物中的三种示例性地应用了主成分分析（PCA），并通过马氏距离图展示了所有聚合物的鉴别情况。
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