Analysis of benzofuran derivatives using electrospray ionization ion trap and electrospray ionization quadrupole time-of-flight mass spectrometry Benzofurans and their analogues constitute a major group of naturally occurring compounds 1 and exhibit anti-tumor activity, 2 anti-complement activity, 3 cytotoxic activity, 4 activity against human leukaemic cells, 5 and antifungal and antibacterial activity. 6,7 Their broad range of biological activities has attracted the attention of synthetic organic chemists, 8,9 and such potential applications point to the need for reliable, fast and low-cost analysis of this class of compounds.Mass spectrometry (MS), especially tandem mass spectrometry (MS/MS), has been one of the important physicochemical methods for the identification of trace natural products due to its rapidity, sensitivity, and low levels of sample consumption, 10-13 and some benzofuran derivatives have been rapidly analyzed using electrospray ionization (ESI)-MS. 14,15 Seeds of the Styracaceae family are known to contain various benzofuran derivatives. [16][17][18][19][20] In our laboratory, a series of benzofuran derivatives ( Fig. 1) was isolated from Styrax perkinsiae and Styrax macranthus 4,18 and, to our knowledge, these compounds have not been studied by ESI-MS/MS. To obtain information on the structural elucidation of this class of compounds, such as their degradation products, metabolites and biosynthesis intermediates, the detailed fragmentation patterns of benzofuran derivatives were studied using ESI-MS n in positive ion mode. For several representative benzofuran derivatives, the elemental compositions of most of the product ions were confirmed by low-energy ESI-MS/MS using a quadrupole time-of-flight (QTOF) instrument.HPLC-grade methanol was purchased from Fisher Scientific (Pittsburgh, PA, USA). The MS n experiments were performed on a Esquire 6000 ion trap (IT) mass spectrometer (Bruker, Bremen, Germany). The capillary voltage was set at 4 kV and the source temperature was maintained at 3008C. High-purity nitrogen gas was used as the nebulizer gas at a pressure of 20 psi. Tandem mass spectra were obtained by collision-induced dissociation (CID) of selected precursor ions with helium as the collision gas, by applying collision voltages between 0.3 and 0.5 V. High-resolution experiments were performed on a Bruker micrOTOF Q (quadrupole time-of-flight) mass spectrometer in positive ion mode. The Agilent (Agilent Technologies, Santa Clara, CA, USA) ESI-MS tuning mixture (ES Tuning Mix, PN G2421A), with reference masses at m/z 322.0481, 622.0290 and 922.0098, was used to calibrate the instrument in positive ion mode. Helium was used as the collision gas and highpurity nitrogen as the nebulizer and drying gas at a pressure of 30 psi. The samples were introduced into the mass spectrometer at a flow rate of 115 mL/h. The ESI source conditions were as follows: capillary voltage, À4500 V; end plate voltage, À4000 V; capillary exit voltage, 120 V; and drying gas temperature, 1508C. The collision energ...