Ambient ionization mass spectrometry: real-time, proximal sample processing and ionization

The definition of ambient ionization is updated from "no sample preparation"to sample preparation proximal and in real time with the ionization and analysis step. We differentiate between ambient ionization methods and the direct and hyphenated techniques. Ambient ionization has been reviewed many times and we summarise some of the approaches that reviews have taken to categorize the many ambient ionization methods. Due to the large number of permutations, frequent redundancy and complexity of the 80+ techniques developed so far, none of the review classifications is successful in classifying all the ambient ionization methods based on the chosen scheme. Likewise our classification based on major sample preparation method also fails at finding a good category for every method, but it does highlight the central role that real- time, proximal sample preparation plays in ambient analysis.