Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission

Abstract

We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces substantive continuum background in the spectral dataset, we show that appropriate treatment of the continuum and characteristic emission results in accurate discrimination of pharmaceutical formulations of similar stoichiometry. Specifically, our results suggest that near-perfect classification can be obtained by employing suitable multivariate analysis on the acquired spectra, without prior removal of the continuum background. Indeed, we conjecture that pre-processing in the form of background removal may introduce spurious features in the signal. Our findings in this report significantly advance the prior results in time-integrated LIBS application and suggest the possibility of a portable, non-gated LIBS system as a process analytical tool, given its simple instrumentation needs, real-time capability and lack of sample preparation requirements.

Signal Enhancement Evaluation of Laser-Induced Breakdown Spectroscopy of Extracted Animal Fats Using Principal Component Analysis Approach

“…Instead of removing the continuum background in the obtained LIBS spectra, the classification of samples was achieved by employing a suitable multivariate analysis on the acquired LIBS spectra. 24 The continuum effect in LIBS spectra also can be reduced by using gated LIBS system. 25

Figure 4.LIBS spectra at wavelength 350–900 nm for frozen extracted (a) chicken fat, (c) lamb fat, (e) beef fat, and (g) lard with enlarged image for emission lines of Ca(I) (445 nm), Mg(I) (518 nm), and Ca(I) (610 nm) in LIBS spectra of frozen extracted (b) chicken fat, (d) lamb fat, (f) beef fat, and (h) lard using both freezing methods.

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“…Instead of removing the continuum background in the obtained LIBS spectra, the classification of samples was achieved by employing a suitable multivariate analysis on the acquired LIBS spectra. 24 The continuum effect in LIBS spectra also can be reduced by using gated LIBS system. 25 The emission lines of elements present in LIBS spectra of extracted animal fats were compared to NIST atomic spectra database as shown in Table III.…”

Less is more: Avoiding the LIBS dimensionality curse through judicious feature selection for explosive detection

“…However, very rarely is there a concerted effort in choosing the features that is rooted in the context of the application (for example, chemical composition of the samples) – rather for reasons of expediency the full LIBS spectrum is routinely employed in classification. Though inclusion of noise 39 and continuum 40 may not significantly hamper the prediction performance in specific cases, feature selection in general is critical to eliminating spurious correlations especially in applications where the inter-class differences are subtle. Here based on the prominent spectral features of CN, C 2 , C, H, O and N, we selected four different regions R1, R2, R3 and R4 as detailed in Table 1 .…”

4S Peak Filling – baseline estimation by iterative mean suppression

“…These are described below, one S at a time. Supporting the descriptions are illustrating figures with spectra from matrix assisted laser desorption/ionisation time-of-flight (MALDI-TOF) [3] and laser induced breakdown spectroscopy (LIBS) [4] . The former is included to illustrate the effects of the different steps of the algorithm, while the latter presents a problem where the proposed method handles a challenging baseline estimation where other tested methods fail.…”