A Comparative Study of Different Methods for Determination of Selenium in Some Sudanese Fruits, Soil and Water

Abstract

This study aimed to measure concentration of selenium (Se) in five Sudanese fruits: Ziziphus spina christi (Nabaque); Adansonia digitata (Tabaldi); Balanites egyptiacea (Laloub); Grewia tenax (Gudeim) and Tamarindus indica (Aradeb). Se concentration was also measured in soil where the plant grows from different depths (75 cm ,100 cm and 150 cm). Also water sample was taken from nearby (Hafeer) to determine Se concentration. All samples were collected according to Standard Method of Sampling. The study area was Alein forest , south east Al-obied city..Se concentration was measured by seven techniques. It was found that the concentration of Se (ppm) increases in the following order: Gudeim (0.0140- 0.0348) >Tabaldi (0.0138 - 0.0344) >Laloub (0.0130- 0.0342) >Aradeb (0.0125- 0.0225) > Nabaque. (0.0122 – 0.0172). It was also observed that the sensitivity of the techniques applied including parentheses the range of its minimum and maximum results obtained in all fruits increased on the following order: hydride generation atomic absorption spectroscopy "HGAAS" ( 0.0172 - 0.0348) > graphite furnace atomic absorption spectroscopy " GFAAS" (0.0162 – 0.0338) > energy dispersive x-rays fluorescence "EDXRF" (0.0154 – 0.0188) > scanning electron microscopy + energy dispersive x-ray fluorescence "SEM+EDS" (0.0150 – 0.0185) > mass-mass inductively coupled plasma "ICP MS/MS" (0.0127 – 0.0145) > inductively coupled plasma optical emission spectroscopy "ICP OES" (0.0122 – 0.0140). Also it was found that the sensitivity of the technique applied for determination of Se in all soil depths (cm )75,100 and 150 for all fruits increased in the following order: HGAAS (0.163 - 0.205) > EDXRF (0.150 - 0.202) > GFAAS (0.153 – 0.201) >SEM+EDS (0.1497- 0.1883) > ICP MS/MS (0.055 - 0.088) >ICP OES (0.050 - 0.085). The concentration (ppm) of Se increased in the order : depths 150 cm (0.069 – 0.195) > 100 cm (0.065 – 0.184) > 75 cm (0.050 – 0.183), for Nabaque and Tabaldi. However, for Laloub it increased in the order: V depth 150 cm (0.071 - 0.194) > 75 cm (0.062 – 0.173) > 100 cm (0.060 – 0.169), and for Gudeim, , Aradeb in the order: depth 75 cm (0.073– 0.205) > 100 cm (0.075 – 0.200) > 150 cm (0.055 – 0.197). For the concentration ranges (ppm) of Se in soils at all depths increased in the following order: Gudeim (0.082 – 0.0205) ˃ Aradeb (0.055 – 0.200) ˃Nabaque (0.065 – 0.192) ˃ Laloub (0.060 – 0.194) ˃Tabaldi (0.050 – 0.195).Technique wavelength dispersive x-ray fluorescence "WDXRF", however, did not detect Se in both soil and fruits samples owing to the dry ashing pre–treating step. Se concentration(ppm) of water were increased as follows: HGAAS,(0.644x10-3) ˃ GFAAS (0.601x10-3) ˃ ICP MS/MS (0.498x10-3) ˃ ICPOES (0.480x10-3) respectively. Techniques SEM+EDS, EDXRF, WDXRF were used only to analyze solid samples. The results obtained for fruits, soil and water were consistent with those of (WHO) Standard and some agreed with those of some obtained of global researches. Se concentration was found to increase in the following order: soil ˃ fruits ˃ water.