We have studied β-decay of 23 Al with a novel detector setup at the focal plane of the MARS separator at the Texas A&M University. Absolute proton-decay branching ratios from excited states of 23 Mg are determined by combining our results to the latest γ-decay data. Contrary to previous β-decay studies, no strong proton intensity from the isobaric analogue state (IAS) in 23 Mg (E x = 7803 keV) was observed. Instead, we assign the lowest observed proton group at E cm = 206 keV to the state 16 keV below the IAS. In this contribution, a description of the used technique along with results of the experiment are given and their relevance for astrophysics discussed.