Especially when many reactions have to be set-up, it has been established to prepare a so-called master mix instead of pipetting each reagent separately into each vessel. Pre-configured mixes are commercially available, in which only sample-specific components (primer) and water are added. Alternatively, the master mix can be prepared by yourself. In both variants, the mixture is distributed to each PCR vessel without a template and the individual DNA sample is added separately at the end.
Using a master mix has several advantages: First, the number of single pipetting steps is reduced. In this way, both the risk of user errors during pipetting and the risk of contamination are minimized and, of course, time is saved. In principle, the pipetting accuracy is also higher, since larger volumes are dosed. This is easy to understand when checking the technical data of pipettes: The smaller the dosed volume, the higher the deviations can be (table 1). The fact that all preparations come from the same vessel has a positive effect on homogeneity (if well mixed). This also improves the reproducibility of the experiments.