Profile differences of trace elements in vegetables and fruits resulting from various digestion procedures

Three pre-treatments of dry ashing, wet ashing and microwave digestion procedures in flame atomic absorption spectrometry (FAAS), were investigated to evaluate their effects on the concentrations of trace elements including Cu, Zn, Fe and Mn for edible plant samples. Microwave was proved to be a good digestion method in the present study due to shorter time, better recoveries and low relative standard deviations (RSDs). For the certified reference materials, RSDs were below 10% and the recovery values of Cu, Zn, Fe and Mn were from 96.63% to 100.00% when microwave digestion procedure was used for pretreatment. Higher trace elements contents were detected when microwave digestion instead of the other digestion methods was chosen to pre-treat spinach or apple samples. The values of the addition recovery in the studied trace elements of Chinese chive or lettuce ranged from 97.00% to 100.00% due to the use of microwave digestion procedure. Therefore, the use of microwave digestion to pre-treat edible plant samples improved the determination accuracy of trace elements in food nutrition assay and concentrations of Cu, Zn, Fe and Mn in investigated edible plants were acceptable to human consumption at nutritional and toxic levels.