Fig 1.
Flowchart of the four different sample preparation methodologies explored for the optimization of chemical process for the lead detection in biological materials A) Acidic dilution B) Addition of a matrix modifier C) Open-vessel acid digestion and D) Microwave assisted acid digestion.
Table 1.
Concentrations of metals used for the selectivity study.
Fig 2.
Optimization of the graphite furnace atomic absorption pyrolysis stage.
Table 2.
Optimal graphite furnace temperature program for the detection of lead and cadmium in E. coli used for microwave assisted acid digestion (optimal method).
Table 3.
Performance of the four sample preparation methods for lead detection in E. Coli.
Fig 3.
Optimization of microwave assisted acid digestion.
a) time of digestion; b) hydrogen peroxide to nitric acid ratio. The optimal settings are boxed.
Table 4.
Comparison between the optimized and initial microwave assisted acid digestion procedure with respect to recovery rates, limits of detection (LOD), limits of quantification (LOQ), and repeatability expressed as relative standard deviation between measurements.
Fig 4.
Optimized microwave assisted acid digestion for determination of lead in E. coli.
Table 5.
Performance of the developed and optimized sample preparation method for cadmium.
Fig 5.
Average recovery rates for lead and cadmium in presence of potentially interfering elements.
The concentration of those elements is shown in Table 1. Each element was investigated first individually and then a mixture of all elements combined.
Table 6.
Cadmium and lead concentrations measured in BCR 679 following the developed sample preparation method.
Please note that only cadmium was certified.