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B. Zachhuber, C. Carrillo-Carrión, B. Simonet, B. Lendl:
"Quantification of DNT isomers by capillary liquid chromatography using at-line SERS detection or multivariate analysis of SERS spectra of DNT isomer mixtures";
Journal of Raman Spectroscopy, 43 (2012), 8; S. 98 - 100.

With the global surge of terrorism and the increased use of bombs in terrorist attacks, national defense and security departments now demand techniques for quick and reliable anal., in particular, for detection of toxic and explosive substances. One approach is to sep. different analytes and matrix material before detection. In this work microliquid chromatog. was used to sep. two dinitrotoluene (DNT) isomers prior to detection via online UV-Vis spectroscopy. For identification, retention times were compared with ref. samples and quantification was done by integration of UV-Vis absorption. Because UV detection is not particularly selective, Raman microscopic anal. was coupled to the liq. chromatog. using a flow-through microdispenser. Because DNT is difficult to detect with conventional Raman spectroscopy, the sensitivity was increased via surface-enhanced Raman scattering (SERS) using silver-quantum dots. Different anal. approaches to identify and quantify mixts. of two DNT isomers were evaluated. Good quant. results were obtained using UV detection after microchromatog. sepn. (Limit of Detection: 0.11 and 0.06 for 2,4-DNT and 2,6-DNT). Coupling with SERS allowed for more confident differentiation between the highly structurally similar DNT isomers because of the addnl. spectral information provided by SERS. The application of a partial least squares algorithm also allowed direct SERS detection of DNT mixts. (root mean square error of prediction: 0.82 and 0.79 mg·L-1 for 2,4-DNT and 2,6-DNT), circumventing the time-consuming sepn. step completely.