Quantitative Analysis of Cadmium in Tobacco Roots Using Laser-Induced Breakdown Spectroscopy With Variable Index and Chemometrics

Abstract

The study investigated some new developed variable indices and chemometrics for the fast detection of cadmium (Cd) in tobacco root samples by laser-induced breakdown spectroscopy. The variables selection methods of interval partial least squares (iPLS), backward interval partial least squares (BiPLS), and successive projections algorithm (SPA) were used to locate the optimal Cd emission line for univariate analysis and to select the maximal relevant variables for multivariate analysis. iPLS and BiPLS located 10 Cd emission lines to establish univariate analysis models. Univariate analysis model based on Cd I (508.58 nm) performed best with the coefficient of determination of prediction (Rp2) of 0.9426 and root mean square error of prediction (RMSEP) of 1.060 mg g−1. We developed two new variable indices to remove negative effects for Cd content prediction, including Index1 = (I508.58 + I361.05)/2 × I466.23 and Index2 = I508.58/I466.23 based on Cd emission lines at 508.58, 361.05, and 466.23 nm. Univariate model based on Index2 obtained better result (Rp2 of 0.9502 and RMSEP of 0.988 mg g−1) than univariate analysis based on the best Cd emission line at 508.58 nm. PLS and support vector machines (SVM) were adopted and compared for multivariate analysis. The results of multivariate analysis outperformed univariate analysis and the best quantitative model was achieved by the iPLS-SVM model (Rc2 of 0.9820, RMSECV of 0.214 mg g−1, Rp2 of 0.9759, and RMSEP of 0.712 mg g−1) using the maximal relevant variables in the range of 474–526 nm. The results indicated that LIBS coupled with new developed variable index and chemometrics could provide a feasible, effective, and economical approach for fast detecting Cd in tobacco roots.

High-Sensitivity Determination of Nutrient Elements in Panax notoginseng by Laser-induced Breakdown Spectroscopy and Chemometric Methods

“…Matrix effects come from the complex plant tissue including differences in chemical compositions and physical properties of plant tissue such as hardness, roughness, porosity, and density [28]. Matrix effects also relate to optical and plasma properties that influence the ratio of a given emission line to the abundance of the element producing that line [27].…”

“…A self-assembled LIBS setup was used to realize LIBS spectral acquisition [28]. Laser pulses at 532 nm with maximum energy of 200 mJ and an 8-ns pulse width were generated by a Q-switched Nd:YAG pulse laser (Vlite 200, Beamtech, Beijing, China).…”

Signal Enhancement of Cadmium in Lettuce Using Laser-Induced Breakdown Spectroscopy Combined with Pyrolysis Process

“…This experiment used a self-assembled LIBS device [27]. A laser pulse with maximum energy of 200 mJ and 8 ns pulse width were generated at 532 nm by Q-switched Nd: YAG pulse laser (Vlite 200, Beamtech, Beijing, China).…”

Quantitative analysis of cadmium in rice roots based on LIBS and chemometrics methods

“…As an element analysis method, laser-induced breakdown spectroscopy (LIBS) technology was proposed by the David Cremers research group of Los Alamos National Laboratory in the United States in 1962 [13,19]. Compared with commonly used chemical detection approaches, LIBS has the characteristics of rapidity, batch, microdamage, multi-element simultaneous analysis and no complex pretreatment [20][21][22]. Recently, LIBS has been used for rapid detection of elements in crops, which has significance for food security and environmental pollution.…”