Evaluation of portable Raman instrumentation for identification of β-carotene and mellitic acid in two-component mixtures with halite.

Recently, portable Raman instrumentation has been in demand for geosciences and for future planetary exploration for the identification of both organic and inorganic compounds in situ on Earth and on other planetary bodies, especially on Mars. Here we present the results of the analysis of halite/β-carotene and halite/mellitic acid mixtures, performed by miniaturized Raman instrumentation equipped with 785 and 1064 nm excitation. Various proportions of organics in the halite matrix were examined. The lowest concentration of β-carotene detected using the 785 nm laser was 1 mg kg(-1), with slightly better signals observed with shorter exposure times compared with the bench instrument using the same excitation wavelength. Mellitic acid was identified at the concentration level 10 g kg(-1). The 1064 nm excitation provided a lower sensitivity towards low concentration when compared with the 785 nm excitation.