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Tetramethylammonium hydroxide assisted solubilisation of peanut for trace element determination using atomic absorption spectrometry

Suvarna Sounderajan, Nitin D Waghmare, Shailaja Pandey and Sanjukta A. Kumar

Tetra Methyl Ammonium Hydroxide (TMAH) assisted solubilisation of peanut sample preparation was evaluated for the determination of Cr, Cu, Fe, Mn, Ni, Pb and Zn using Graphite Furnace Atomic Absorption Spectrometer (GFAAS) and Na, K, Ca and Mg using Flame Atomic Absorption Spectrometry (FAAS). In the alkaline solubilisation with TMAH, 0.25 g of the sample was heated to 90 ± 3°C for 2h in the presence of 500µL of 25% TMAH solution in aqueous medium. The procedure provided complete solubilisation of the sample. The particle size of the slurry was in the range from 0.2µm to 14 µm with mean size of 1.5 µm, suitable for injection with auto sampler. The LOD and LOQ for peanut slurry samples prepared in TMAH for the respective elements ranged from 0.0002 to 0.0658 and 0.0005 to 0.2343 mg L-1, respectively. The instrumental RSD of the detected elements ranged from 0.11 to 0.81%. The proposed method was compared with complete microwave acid digestion method and the t-values obtained were in the range of 0.08 to 2.03 against critical value t10 = 2.23 (P = 0.05), suggesting no significant difference in the values obtained from both the method. SRM- 2387-Peanut butter (NIST) was utilized for validation of the proposed method. The z-scores for values obtained were within ± 1 which indicates accuracy of the TMAH alkaline solubilisation. In comparison to complete acid dissolution method, the proposed TMAH alkaline solubilisation method is simple, requires less reagents and time which in turn minimises contamination risk. The simplicity of the proposed method makes it attractive and an excellent alternative for the preparation of peanut samples for elemental analysis using Atomic Absorption Spectrometry.