The parameters that have the most influence on the MS signal, namely the cone voltage, desolvation temperature, extractor voltage and multiplier voltage, were further optimised by means of a central composite design. The design allowed to model the response surface by fitting a second-order polynomial model. The statistical analysis of the model gave R2 values of 0.97–0.99 and Q2 values of 0.79–0.91. The R2 value corresponds to the fraction of the variation of the response which can be explained by the model, while the Q2 value corresponds to the fraction which can be predicted by the model. The obtained Q2 values are close to one, which indicates the suitability of the model for predicting the optimal conditions.