NEW METHODOLOGY FOR CHECKING OF ABSENCE OF THE SYSTEMATIC-ERRORS IN THE DETERMINATION OF SULFATE ION IN MGCL2.6H2O

A new methodology is proposed for obtaining analytical results free fr om bias errors, it is based on a modification of the standard addition method. Bias or systematic errors are taken as the differences betwee n the amounts of analyte in the test portion and the image of the anal ytical signal on a calibration relationship where the amounts of added analyte act as the predictors. The constant component of the error, t he matrix interactive effect and the direct matrix interference are jo intly discussed as the main sources of bias. The latter two are consid ered to be different forms of interference. As an example, the new met hodology was applied to the determination of sulphate ion in a magnesi um chloride sample (Merck AR) using a spectrophotometric and an atomic absorption spectrophotometric procedure. No direct matrix interferenc e or interactive matrix effect on the analytical results was found.