Froelich Noah M, Azcarate Silvana M, Goicoechea Héctor C, Campiglia Andrés D
Chemistry Department, University of Central Florida, Orlando, Florida, USA.
Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Instituto de Ciencias de la Tierra y Ambientales de La Pampa (INCITAP), Santa Rosa, La Pampa, Argentina.
Appl Spectrosc. 2024 Sep;78(9):962-973. doi: 10.1177/00037028241255150. Epub 2024 May 22.
Fluorescence spectroscopy is an attractive candidate for analyzing samples of nylon. Impurities within the polymers formed during the synthesis and processing of nylons give rise to the observed fluorescence, allowing for nylons to be analyzed based on their impurities. Nylons from the same source are expected to display similar fluorescence profiles, and nylons with different fluorescence are expected to be from different sources. This paper investigates an important case where different nylons displayed similar fluorescence, preventing easy discrimination. Samples of Nylon 6 and Nylon 6/12 had visually indistinguishable excitation-emission matrices (EEM), excitation spectra, fluorescence spectra, and synchronous fluorescence spectra at larger Δλ. By collecting synchronous fluorescence spectra at smaller Δλ, additional features in the fluorescence profiles were identified that allowed for some discrimination between the two nylons. Combining the EEM and synchronous fluorescence data with chemometric algorithms provided a clearer differentiation between the two nylons. parallel factor analysis, principal component analysis, and common dimension partial least squares (ComDim-PLS) showed two distinct clusters in the data, with ComDim-PLS providing the greatest distinction between the clusters. The loadings revealed the variables of interest to the ComDim-PLS were the 400 nm and 335 nm bands for all synchronous fluorescence spectra, the 460 nm and 310 nm bands for the Δλ = 20 nm and Δλ = 30 nm synchronous fluorescence spectra, and the 440 nm band for the Δλ = 20 nm synchronous fluorescence spectra. The linear discriminant analysis performed with the PLS data yielded a classification accuracy of 95% with the EEM data and 100% with the synchronous fluorescence data, displaying the power of this technique to differentiate two different nylons with visually indistinguishable fluorescence spectra.
荧光光谱法是分析尼龙样品的一种有吸引力的方法。尼龙在合成和加工过程中形成的聚合物中的杂质会产生观察到的荧光，从而可以根据尼龙中的杂质对其进行分析。预计来自同一来源的尼龙会显示出相似的荧光光谱，而具有不同荧光的尼龙预计来自不同的来源。本文研究了一个重要的案例，即不同的尼龙显示出相似的荧光，难以轻易区分。尼龙6和尼龙6/12的样品在较大的Δλ下具有视觉上无法区分的激发-发射矩阵（EEM）、激发光谱、荧光光谱和同步荧光光谱。通过在较小的Δλ下收集同步荧光光谱，在荧光光谱中识别出了额外的特征，从而能够对这两种尼龙进行一定程度的区分。将EEM和同步荧光数据与化学计量算法相结合，可以更清晰地区分这两种尼龙。平行因子分析、主成分分析和共同维度偏最小二乘法（ComDim-PLS）在数据中显示出两个不同的聚类，其中ComDim-PLS在聚类之间提供了最大的区分度。载荷显示，ComDim-PLS感兴趣的变量是所有同步荧光光谱的400 nm和335 nm波段、Δλ = 20 nm和Δλ = 30 nm同步荧光光谱的460 nm和310 nm波段以及Δλ = 20 nm同步荧光光谱的440 nm波段。使用PLS数据进行的线性判别分析在EEM数据上的分类准确率为95%，在同步荧光数据上的分类准确率为100%，显示了该技术区分两种具有视觉上无法区分的荧光光谱的不同尼龙的能力。
