Changes in the analytical performance of double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS) caused by addition of methane to the argon gas ICP were studied for approximately 100 isotopes of 70 elements. The parameters under consideration included instrumental background, analyte sensitivity, precision and formation of spectral interferences as functions of methane flow added to the sample gas. It was shown that for many analytes the capabilities of ICP-SFMS significantly improve by virtue of enhanced sensitivity and reduction of polyatomic interferences. In contrast to quadrupole-based ICP-MS, these gains in instrumental performance do not compromise multi-element capabilities given that the amount of methane is carefully optimized. The accuracy of the results for the determination of 50 elements in water samples was evaluated using the certified reference materials SLRS-4 and SLEW-2.