The operating conditions of an inductively coupled plasma atomic emission spectrometer have been optimised for signal to background ratio, using the variable step-size simplex technique for the introduction of a variety of organic solvents for two analytical lines with different excitation energies, Cu I 324.754 nm and Mn II 257.610 nm. The parameters optimised were inner gas flow, intermediate gas flow, outer gas flow, forward power, viewing height and spray chamber temperature (–25 to +55 °C). For solvents of high volatility, lower carrier gas flows and spray chamber temperatures were preferable. Lower power was found to be optimum for organic solvents compared with water, and also for “hard” lines compared with “soft” lines. Additionally, lower detection limits were calculated for the two elements studied in organic solvents compared with water. It is clear that the vapour loading in the plasma critically affects analytical performance.