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An interference-free atomic absorption method for the determination of total iron in geological samples has been adopted. The method is based on the conventional standard curve technique employing the 386 nm atomic absorption line in the fluoboric-boric acid matrix. The use of the 386 nm line instead of the 248.3 nm line is discussed, as well as the advantages of the hydrofluoric acid dissolution of the sample. A comparison of different methods is given in search of one for routine determinations in this laboratory. Interference studies of aluminum and/or silicon on the iron determination conclude that these interferences do not exist under the conditions of this method. The literature on such interferences is reviewed and they are discussed. The proposed method was used to determine total iron in six reference materials and the results were in good agreement with the reported values. Finally, total iron was determined in a preliminary profile of Venezuelan laterites (ferrouginous bauxites).

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A method to overcome the numerous interferences present for the determination of titanium in Venezuelan laterites and bauxites has been adopted. The technique is based on dissolving the sample in the HF-H3BO3 matrix. The advantages of using this system are discussed. After the sample is decomposed in this system, 1 part of 2000 ppm of Al, Si, and Fe in the same system is added to 9 parts of the decomposition solution. The atomic absorption determination is employed using the conventional standard curve method for the 364.3 nm line. A comparison of this method with x-ray fluorescence and colorimetry is given in search of one method for routine batch determinations. Interference studies of aluminium, silicon, and iron, the common major elements in Venezuelan laterites and bauxites, conclude that both aluminum and iron greatly affect the absorption signal for titanium. The proposed method, as well as x-ray fluorescence and colorimetry, was applied to standard reference rocks and a preliminary profile of Venezuelan laterites (ferrugineous bauxites).

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