Lc system lc 20ad

The reaction products derived were quantified by liquid chromatography-mass spectrophotometry (LC-MS). Firstly, samples withdrawn from the reactor were filtered through a 20-25 μm filter (NO 541 Hardened Ashless, and 110 mm diameter, WhatmanTM Co., Marlborough, MA, USA) to remove the spent catalyst. Then, the filtered solution was diluted 10-fold with HPLC grade water, followed by centrifugation using ultracentrifugation filters (Amicon^® filters, Merc Millipore, Billerica, MA, USA) at 9000 rpm for 10 min (accuSpin Micro 17R, Fisher Scientific, Waltham, MA, USA). After centrifugation, the precipitate was discarded, while the supernatant was used for analysis. An aliquot of 10 µL from the supernatant was injected into a Shimadzu LC system (LC-20AD, Shimadzu Corp, Kyoto, Japan), combined with a Qtrap 5500 triple quadrupole mass spectrometer (AB Sciex, Foster City, CA, USA). Analytes were eluded by means of an HPX-87C column (250x4.0 mm, Bio-Rad Aminex, Hercules, CA, USA) operated at 80 °C with a mobile phase consisted of acetonitrile: water (20:80 v/v), at a flow rate of 0.2 mL/min. Mass spectrophotometer analysis was operated in negative mode at a temperature of 500 °C, a curtain gas of 30 psi, an ion source gas of 15 psi for nebulizer (GS1), and heater (GS2). Samples were quantified according to HPLC-grade analytical standards.