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Abstract
Preparative isolation of avermectins B1a and B1b has been successfully performed using high-speed countercurrent chromatography coupled with electrospray mass spectrometry (HSCCC/ESI-MS). The analytes were purified on a HSCCC model CCC-1000 (multi-layer coil planet centrifuge) with a volatile two-phase solvent system composed of hexane/ethyl acetate/methanol/0.5% formic acid in water (7/3/5/5, V/V) and detected on a quadrupole MS fitted with an ESI source system in positive ionization following scan mode (m/z 600–1200). The HSCCC/ESI-MS peaks indicated that avermectins B1a (m/z 891:[M+NH4]+) and B1b (m/z 877:[M+NH4]+) have the peak resolution value of 3.3 from 10 mg of loaded abamectin standard. The HSCCC yielded 8.2 mg of avermectins B1a and 0.8 mg of B1b. These purified avermectins were evaluated by LC/MS with scan positive-mode. Based on the LC/MS chromatograms and spectra of the fractions, analytes were estimated to be over 98% purity. These results indicate that this approach of HSCCC/MS is a powerful technique for the purification of main components in abamectin.
