Ambient ionization coupled to mass spectrometry has the advantages of minimal requirements for sample preparation prior to analysis which renders it suitable for high throughput screening. We present a protocol that permits the application of this method in routine biotechnology and chemical biology laboratories which are using engineered enzymes to produce target compounds from substrates. We show how DESI-MS can be used to directly analyse the activity of biotransformations from crude cell lysate which we term DiBT-MS, this method is 10-1000 times faster than LC-MS and uses far less solvent. This protocol demonstrates the impact of solvent spray composition on ionization efficiency of the target analyte, the benefits of a nylon membrane slide and the reusability of sample slides in multiple experiments.
Mass spectrometry data in support of the main text.