Micromass lct premier xe mass spectrometer

The UPLC-TOF-MS system consisted of an ACQUITY^™ Ultra Performance Liquid Chromatography (UPLC) system and a Micromass LCT Premier XE Mass Spectrometer (high sensitivity orthogonal time-of-flight instrument, Waters, Milford, USA) equipped with a lock mass sprayer, operating in either positive or negative ion mode. All analyses were acquired using the lock spray to ensure accuracy and reproducibility; leucine enkephalin was used as the lock mass. High resolution (W mode, FWHM 10500) positive polarity scan responses were collected from m/z 100 to 1000 at a rate of 1.0 s/scan. The chromatographic column used was an ACQUITY UPLC™ BEH shield RP18 (2.1 × 100 mm, 1.7 μm). Mobile phase A contained 0.1% TFA and mobile phase B contained a mixture of 0.1% TFA and acetonitrile in the ratio of 10:90 (v/v), respectively. The gradient program (time (min) / %B) was set as 0/45, 2/53, 2.5/80, 3/95, 5/100, 5.1/45, and 7/45 with a flow rate of 0.4 mL/min and injection volume of 2.0 µL. The mobile phases were filtered through nylon 0.45 mm membrane filters and degassed. The column temperature was maintained at 50°C and the peaks were monitored at 210 nm. The optimized LC conditions are described in Table 2. A mixture of water and methanol in the proportion of 50:50 (v/v) was used as diluent for sample preparation.

All starting materials and reagents were obtained commercially and used without further purification unless otherwise specified. 4 Å molecular sieves were flame-dried under vacuum and cooled to rt under a N₂ atmosphere immediately before use. The reactions were monitored by thin-layer chromatography (TLC) on glass-packed precoated silica gel plates and visualized with a UV detector or charring with 10% H₂SO₄ in EtOH (v/v). The purification of products was accomplished by flash column chromatography on silica gel (200–300 mesh). NMR spectra were recorded on a Bruker Avance III 400 or Avance II 600 spectrometer (¹H at 400 or 600 MHz, ¹³C at 100 or 150 MHz) with chemical shifts reported in ppm using TMS as the internal standard. Signal splitting patterns are described as singlet (s), doublet (d), triplet (t), quartet (q), or multiplet (m), with coupling constants (J) in hertz. MALDI-TOF mass spectrometry was performed with a Bruker Ultraflex instrument by applying the matrix of 2,5-dihydroxybenzoic acid (DHB). The high resolution electron spray ionization mass spectra (HR-ESI-MS) were obtained using a Waters Micromass-LCT Premier-XE mass spectrometer.