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Thorium is a naturally occurring radioactive element that is widely distributed in the crust of the Earth. This element is very common in mineral formations in regions with high levels of natural radioactivity, therefore, its determination in environmental samples is important. Thorium isotopes (228Th, 230Th, and 232Th) were determined in a reference material, the IAEA Soil 327 sample, to validate the two methods, these isotopes were also analyzed in two groups of food samples, employing these different resins. The initial preparation with acid dissolution is the same to both, in the first is used anion exchange resin (DOWEX 1x2) and electrodeposition in silver planchets. And in the second method is used a specific chromatographic resin (TEVA) and cerium fluoride microprecipitation. At the end both analysis are quantified by alpha spectrometry. The two methods the results obtained were satisfactory for the reference material used, with relative error of less than 4% for 228Th, 230Th, and 232Th. The analysis of variance for samples foods analyzed seen to be no significant difference between the methods used for thorium isotopes determination. The main differences found between methods were spectrums resolutions, time and cost of analysis.

The quick determination of natural radionuclides is very important in emergency situations, supporting decisions of environmental contamination prevention. A quick methodology for determination of the 226Ra was applied in water samples and the results were compared to those obtained by the conventional method. The technique is based on the microprecipitation of radio barium sulfate and subsequent quantification of 226Ra by alpha spectrometry. The procedure used presented high chemical recoveries and good sensitivity. The main advantage is to obtain the results in 3 days.

This study determined the concentrations of 234U, 235U, 238U, 228Th, 230Th, 232Th, 226Ra, 228Ra, and 210Pb in 82 types of food, grouped into 19 groups according to the Brazilian Total Diet, which reflects the dietary habits of the Sao Paulo State population. Radionuclides were quantified using Ultra low level alpha and beta total counting, and alpha spectrometry, after radiochemical separations. The results of this preliminary work showed that the food groups analyzed gave a consumption of effective dose lower than the dose limit for the public, of 1 mSv year−1.