Unlike previous methods, Auto-VTNA can be used to identify the order values which optimise concentration profile overlay for several reaction species in the same calculation. The basic workflow is demonstrated in Figure . Firstly, a mesh with a selected number of order values within a specified range is defined, e.g. from -1.5 to 2.5 (step 1). Secondly, a list of every combination of reaction order values for each normalised species is created (step 2). For each combination of orders, the Please do not adjust margins Please do not adjust margins time axis is normalised, and the transformed concentration profiles fitted to obtain the overlay score (step 3 and 4). This reveals the optimal order combination around which a new collection of order value combinations is generated to increase the precision with which the optimal reaction orders are determined (steps 5 and 6). This procedure is repeated a selected number of times to increase precision without an unacceptably high processing time (see ESI, Section S5).