Validation of microwave-assisted wet digestion of natural rubber for ICP-AES mineral analysis

Abstract

The mineral composition of three types of Hevea latex samples was determined by inductively coupled plasma atomic emission spectroscopy using a microwave-assisted wet digestion method. This method was compared in Round Robin tests to a dry reference method used to analyze leaf minerals. The results show on the one hand that for all elements, the methods studied are robust in terms of performance. Indeed, the low z scores obtained on the reference sample for both methods prove the accuracy of the methods studied. On the other hand, the results of the percentages of Mg, P and K obtained by the wet method are 5 to 10% higher than those obtained by the dry method. This significant difference shows that the wet method is more efficient than the dry method due to less loss of elements and can be used to quantify all elements of interest, especially sulphur, which to date had remained non-quantifiable by the dry method. The results confirmed the technique to be reliable, easy to use in the laboratory, and relatively mild in terms of chemicals However, certain limitations were found for calcium where, given the low contents and heterogeneity of the materials, inductively coupled plasma mass spectrometry, which is more suited to trace analyses, remains the preferred method.