It is crucial to make comprehensive assessments of soil under economic and efficiency requirements in order to guide the rational use of soil resources, including the identification of attributes, the control of pollutants, and the management of nutrients. Laser induced breakdown spectroscopy (LIBS) is excellent for such applications due to its unique advantages of simple preparation, rapid measurement, and multiple-element analysis. An analysis of Si, Al, Mg, Ca, Na, K, Mn, Ba, Ti, Cr, Cu, Sr and P in different standard soils using LIBS is reported here for the comparison of the quantitative results of a univariate regression method (calibration curve) and two multivariate regression methods (partial least squares regression (PLSR) and support vector regression (SVR)). As a result, the correlation coefficients (R²) of the Ca, K, Mg, Na and Sr elements were all greater than 0.90, while the calibration curves of Al, Ba, Cr, Cu, Mn, Ti and P presented poor linear performances with low R² values of below 0.90. The robustness of the SVR model was superior to the PLSR model with a better prediction ability and a lower relative standard deviation (RSD) for both the training data and the test data, whilst the opposite was observed for the predicted data set used as external verification. The predicted relative errors of the prediction data given by PLSR for all analysis elements except Na and K were lower than those given by SVR. The relative errors of PLSR for Si, Al and Sr were within 10%, while the values for the other elements were between 10% and 20%, and 45% for Cu. It is therefore meaningful to propose a quantitative reference among the univariate linear regression, the multivariate linear regression and the multivariate nonlinear regression methods for the multi-element analysis of soil samples under complex matrix conditions.

A modern trend in the development of laser-based analytical instruments is to integrate more functions in a single device, which could supply complementary information and improve the capability to identify different components. This review presents historical development of the combined analysis by laser-induced breakdown spectroscopy (LIBS) and Raman Spectroscopy, which briefly describes basic instrumental principles and technological aspects of the hyphenated technique, as well as the requirements in the design of interactive instruments, including laser systems, optical systems for laser beam delivery, emission collection devices, and spectrum measurement systems. Various configurations of the combined instrumentation have been designed and used depending on the different applications, such as pigment analysis in the cultural heritage field, detection of explosives, analysis of geological samples, and applications in future planetary missions. In addition, the feasibility, applicability, and prospective aspects of the hybrid technology are discussed in detail.