Abstract:
Rice is the most important staple food crop for more than half of the world’s population. In this
study, proximate and elemental composition of rice collected from three study sites: West
Dembia, East Dembia and Fogera districts in the Central- and South-Gondar Administrative
Zones, Ethiopia, were analyzed. After proper sample pretreatment, a 0.5 g of oven-dried rice
sample was digested with an optimized wet-digestion procedure using 3.5 mL of HNO3, 1.5 mL
of HClO4 and 0.5 mL of H2O2 at 175 °C for 1:55 h; and validity of the procedure was evaluated
by spiking experiments. The concentrations of essential- (Zn, Cu and Mn) and non-essential (Pb
and Cd) metals were determined by flame atomic absorption spectrophotometer. Results of
proximate analyses showed that moisture and ash contents varied from 11.1 to 12.3% and 0.96 to
1.77%, respectively. With respect to metal analyses, the percentage recoveries ranged from 92.5
to 98.0%, indicating good accuracy and repeatability of the optimized procedure. The
concentrations of metals (mg/kg) in rice samples from the three study sites ranged from: Zn
(50.5–52), Cr (19.9–30.5), Mn (21–22.6), Cu (1.22–1.49), Pb (1.24–1.49), and Cd (1.1–1.14).
One-way ANOVA revealed significant differences (p < 0.05) among the mean concentrations of
metals in all rice samples; while insignificant differences were observed for metal values among
the three study sites, indicating absence of effect of geographic origin on the metal levels. The
concentrations of metals observed were comparable with some of the reported values in the
literature. The levels of Cr, Cd and Pb, were above the permissible limit set by WHO/FAO,
except for Cr in rice samples from Fogera district. Thus, special concern should be paid on the
consumption of rice from these study areas since they were found to contain higher levels of
toxic metals, especially Cd and Pb. Hence, a complete risk assessment is required
