Updated project metadata. Gene expression is driven by the binding of transcription factors to regulatory elements in the genome, such as enhancers and promoters. A powerful technique to study DNA-protein interactions is affinity purification followed by mass spectrometry. Classic affinity purifications coupled to quantitative mass spectrometry provide information about binding specificity. Binding of transcription factors to regulatory elements in vivo, however, also depends on binding affinity, so the strength of an interaction. To obtain this information, we recently developed a technique called PAQMAN that uses a series of DNA affinity purifications to quantify apparent binding affinities proteome-wide. Here, we expand our PAQMAN workflow to obtain information about binding specificity and affinity in a single experiment. To this end, we combine quantitation at the MS1 level with quantitation at the MS2 level, a strategy that is known as higher order multiplexing. This is, to our knowledge, the first time that higher order multiplexing is applied to affinity purification - mass spectrometry experiments. In the future, we anticipate that this new workflow will be a useful tool to investigate transcription factor biology.