ABSTRACT
Ethiopia is the world's largest producer of teff (Eragrostis tef Zucc). This research was intended to determine the levels of mineral nutrients (metals and nonmetals) and nonessential metals in the grains of teff. Following the optimization of the method, the samples were wet-digested using reagents (5-mL HNO3 and 1-mL HClO4) at a temperature of 230°C for two and a half hours and analyzed using inductively coupled plasma-optical emission spectrometry. Under the optimum procedure, the coefficients of determination (R 2) ranged between .9980 and .9999. The limits of detection and limits of quantification were in the range of 0.036-14.49 and 0.111-43.93 mg/kg, respectively. The recovery ranged from 80.72% to 107.79%, indicating that the method was accurate. The optimized and validated method was applied to quantify the levels of analytes in the teff samples. The overall mean concentrations of the analytes in the three varieties of teff samples were determined (mg/kg) to be in the order P (3890-4853) > K (3040-3784) > Ca (1906-1959) > Mg (1402-1698) > Fe (128-305) > Mn (64-127.8) > Na (50-136.5) > Zn (19.8-27.3) > B (1.8-21.9) > Cu (4.17-6.9) > Ni (2.6-4.05) > Hg (1.8-4.0) > Pb (0.048-3.7) > Cd (0.012-2.09) > As (0.02-0.24), with a % RSD ranging between 0.017 and 11.1. The results revealed that teff grains are a good source of minerals and contain a significant amount of toxic elements, such as Cd, Hg, Pb, and As.
ABSTRACT
Methods have been developed for the hydrolysis and derivatisation of protein-bound metabolites of nitrofurans and for the extraction of 2-nitrobenzaldehyde derivatives of the metabolites from chicken meat. In this work, the time needed for hydrolysis and derivatisation was reduced from the conventional 16 h to 90 min. Based on partitioned dispersed liquid-liquid microextraction, a method for extracting 2-nitrobenzaldehyde derivatives of metabolites from crude chicken meat has been developed. Under the optimised experimental conditions, enrichment factors (EFs) ranging from 92.8 to 208.9 were obtained. The method was linear over the range of 10-600 µg kg-1 with determination coefficients (r2) between 0.9979 and 0.9996. Intraday and interday repeatability expressed as a percentage RSD, ranged from 2.2% to 11.2%, and 2.7% to 12.4%, respectively. LOD of 1.07-2.25 µg kg-1 and LOQ of 3.09-6.2 µg kg-1 were obtained. The proposed method was applied in the analysis of metabolites of nitrofurans in chicken meat obtained from farmers using them for their domestic consumption and proved free of the analytes. A recovery of 85.2-109.4% with a %RSD ranging between 3.4% and 13.7% was obtained at three spiking levels. The proposed method was successfully further applied for the analysis of target analytes in chicken meat samples purchased from different supermarkets around Roodeport, Gauteng (South Africa). There was no target analyte detected in the analysed samples. Therefore, the developed methods can be used for monitoring the corresponding metabolites of nitrofurans in chicken meat.
