Direct mass spectrometry analysis of untreated samples of ultralow amounts using extraction nano-electrospray

Abstract

Direct mass spectrometry analysis of untreated samples of volumes as low as 0.2 μL was achieved using fast extraction and nanoESI (electrospray ionization) in a combined fashion. The analytes in dried samples on paper substrates were extracted by an organic solvent in a nanoESI tube and ionized with a high voltage applied for generating a spray. The ionization source produced stable signals for different atmospheric pressure interfaces of triple quadrupole instruments. Analysis times more than 20 minutes were available with 10 μL solvent consumed for the entire analysis process. The performance in qualitative and quantitative analyses was characterized with a wide variety of samples. Limits of detection as low as 0.1 ng mL⁻¹ (corresponding to an absolute amount of 0.05 pg) were obtained for analysis of atrazine in river water, thiabendazole in orange homogenate, and methamphetamine in blood.