Selenium determination in biscuits and pasta: Development of chronopotentiometric stripping determination by using a sulphide as an internal standard

In this work the possibility of using sulphide for selenium quantification by chronopotentiometric stripping analysis was investigated. Optimal experimental parameters were defined in two-component systems. Dimensionless factors defining the ratio of proportionality constants of the two elements were calculated for different selenium concentration ranges at different sulphide contents. Sulphide content that was chosen as adequate for selenium concentrations reasonably to be expected in food samples was 500 µg/dm3. Determined detection limit of chronopotentiometric stripping determination of selenium by using a sulphide as an internal standard was 0.04 µg/dm3 (RSD=7.6%; n=5). Defined quantification method was confirmed by analysing spiked standard solutions and standard reference material. The method was used for selenium determination in biscuit and pasta samples. Calculated contents were statistically compared with those obtained by using graphite furnace atomic absorption spectrometry.