This work investigates the use of an unconventional reference material to determine experimentally the Cliff-Lorimer factor for EDS quantitative analysis with a transmission electron microscope. The results demonstrate the equivalence of a bi-layer of pure gold on pure silver with respect to a binary alloy foil of the same elements. RF-sputtering is a suitable technique to prepare such reference materials that have a uniform thickness within a few percent tolerance. The availability of a calibrated set of similar reference materials would allow direct measurement of the k-factors for a large number of elements. This would avoid the errors due to the use of theoretical k-factors extracted from the compilations available in the literature. A new expression of the correction factor for X-ray self-absorption of the sample has also been derived.