Ultrasonic sample introduction combined with flame assisted thermal ionization: Pretreatment-free direct mass spectrometry analysis for fraction collecting tubes of preparative liquid chromatography.

Ultrasonic sample introduction combined with flame assisted thermal ionization mass spectrometry (USI-FATI-MS) was developed to monitor the fractions of preparative liquid chromatography. Recently, ultrasound-based sample introduction techniques have achieved great advance in the field of high-throughput analysis. However, it is still a challenge to directly apply these existing techniques to the analysis of macro volume samples (mL level). In this work, ultrasonic sample introduction combined with flame assisted thermal ionization was used for pretreatment-free direct mass spectrometry analysis of micro to macro volume samples (μL-mL level). Utilizing this unique design of ultrasonic sample introduction, liquid sample in the container can be quickly atomized to the gas phase without contact. Then, due to the flame assisted thermal ionization source, desolvation and ionization of the sample droplets will occur immediately. USI-FATI-MS has shown excellent sensitivity, repeatability and great compatibility to solvents and compounds with a wide range of polarity. As a proof of concept, USI-FATI-MS has been applied for rapid monitoring and identification of purified synthetic and natural products in fractions.