Bruce S. MacDonald

Gravimetric approach to the standard addition method in instrumental analysis. 1.

A mathematical formulation for a gravimetric approach to the univariate standard addition method (SAM) is presented that has general applicability for both liquids and solids. Using gravimetry rather than volumetry reduces the preparation time, increases design flexibility, and makes increased accuracy possible. SAM has most often been used with analytes in aqueous solutions that are aspirated into flames or plasmas and determined by absorption, emission, or mass spectrometric techniques. The formulation presented here shows that the method can also be applied to complex matrixes, such as distillate and residual fuel oils, using techniques such as X-ray fluorescence (XRF) or combustion combined with atomic fluorescence or absorption. These techniques, which can be subject to matrix-induced interferences, could realize the same benefits that have been demonstrated for dilute aqueous solutions.

Software Package to Facilitate the Preparation of Intermediate-Range Fossil Fuel Standards from Certified Reference Materials

A PC software package has been developed in Visual Basic for Applications to assist analysts in mixing fossil fuel reference materials to produce standards of intermediate concentrations. Mixing appropriate reference materials of similar matrices permits the analyst to produce needed standards over a continuous concentration range for analytes of interest. The program automates selection of optimum mixtures and calculates the concentrations and associated uncertainties of analytes in the blends. A graphical interface depicting all possible blends and an automated quality control test to monitor the process for potential problems are included.