Desorption electrospray ionization ambient mass spectrometry

Ambient mass spectrometry is a useful and rapidly growing new field that provides high sensitivity mass spectra directly from surfaces at atmospheric pressure. Various ionization techniques, including desorption electrospray ionization (DESI), direct analysis in real time (DART), plasma assisted desorption ionization (PADI) and extractive electrospray ionization (EESI) have been used. This paper refers particularly to the fundamentals and applications of DESI-MS based on imaging mass spectrometry. Among other applications, DESI is used for direct analysis of drugs and pharmaceutical formulations, samples of biological fluids, forensics, fingerprints, food, cultures of bacteria, identification and spatial distribution of chemicals in animal and plant tissues, and molecular biomarkers. It highlights the possibility of combination with thin layer chromatography and electropherograms to identify the compounds by mass spectrometry. This technique requires no sample preparation, and does not involve the use of matrix of ionization. It simplifies greatly the experimental procedure and avoids the redistribution of analytes during matrix deposition. The forensic analysis carried out by DESI-MS and DESI-MS/MS is discussed, including the detection of explosives and chemical warfare agents on solid surfaces near or at a distance from the mass spectrometer, analysis of fabric or clothing for explosives and drugs, image analysis for verification of documents, analysis of human skin, gunshot residue analysis, analysis of toxic gases and industrial warfare agent simulants, petroleum distillates and synthetic polymers. Aplications in the field of lipidomics, proteomics, and metabolomics are analyzed. Finally, current information on the quantitative analysis performed by DESI-MS is provided.