Characterization of Gum Arabic Using Laser Induced Breakdown Spectroscopy LIBS

Abstract

The aim of this work was to characterize the Gums Arabic, by using Laser Induced Breakdown Spectroscopy (LIBS) technique. This method gives a clear picture of the components of Gum Arabic and does not change the nature of the materials. Three types of Gum Arabic were used in this work; Acacia Senegal, Acacia Seyal, and Acacia nilotica var. nilotica. Five samples from each type were collected from five different locations in Sudan: (South Kordofan, North Kordofan, Blue Nile, White Nile and Gadaref). These samples were irradiated by Nd: YAG laser at 1064 nm, Repetition Rate (RR) = 2Hz, pulse duration 10 ns, with pulse energies of (60, 80, 120, and 180 mJ) for each sample. The analysis of the spectra was done by using Atomic Spectra Database line of National Institute of Standard and Technology (NIST) which showed that the sample contain considerable amounts of neutral atoms like Fe, Na, Ca, Mg, K, S, C, N, O,P, Cr, Br, Ti, Ar, and H in Acacia Senegal (Hashab). While in the Acacia seyal (Talha) sample the detected elements are: Fe, Na, Ca, Mg, K, S, C, N, O, Cr, Br, Ti, Ar, H, P and Th. All elements which were found in the Acacia Senegal (Hashab) appeared in Acacia nilotica samples beside the following elements: Co, Kr, Sc, Mn and Pr. Also the elemental analyses of gum samples by LIBS provided a supportive evidence for the presence of heavy metals like: Fe, Th, Pr and Cr. It is interesting to report, for the first time, the presence of Br, Ar, Ti and Th. It also of interest to note the presence of higher ionization states of some of the elements present in the gum samples such as Fe+3, Fe+2, Cr+3, Th+2, Ca+2, Cr+5,Ti+2 and Ti+3. The gum Arabic investigated in this study showed elements with high concentrations like H, O, C, S, N and elements with low concentrations like Na, Ti and Mg. Using LIBS technique in this study enabled obtaining superior results compared to other techniques and allowing for the observation of some elements in Gum Arabic that are reported for the first time. Increasing the laser energy results in improving the detection of the elements by generating positive ions which gives emission lines that conform the presence of the element in the sample. Samples of Acacia nilotica showed the presence of heavy metals like Fe, Cr, Pr and Th which may hinder its application in food and pharmaceutical formulation. The results obtained from this study suggest a further elaborate investigation of the optical properties of Gum Arabic and how the influence its color.