Rapid Analysis of Volatile Fatty Acids in Feces by Headspace Gas Chromatography Tandem Mass Spectrometry / 分析化学

ABSTRACT

A rapid headspace gas chromatography tandem mass spectrometric ( HS-GC/MS ) method was established for the analysis of volatile fatty acids ( VFAs ) in the feces. Feces were suspended by 6%phosphoric acid aqueous solution (12 m/V) and sealed in the headspace bottle for HS-GC/MS analysis. The HS-GC/MS method was optimized as follows agitator temperature ( temp. )80 ℃, syringe temp.80 ℃, sample incubation time 30 min, injection 1 mL without split-flow. The chromatographic separation was performed on a DB-FFAP capillary column (30m×0. 25 mm×0. 25 μm) with injection port temp.250 ℃. The temperature program ( initial temp. at 50 ℃ within first 1 min, and raised to 200 ℃ by 10 ℃/min) was employed by fixing the flow of carrier gas (high purity helium) at 1. 0 mL/min. The electron energy at -70 eV for electron impact ( EI ) ionization, ion source temp. 250 ℃, transfer line temp.280 ℃, the voltage of electron multiplier at 0. 95 kV. The spectra were recorded in the range of m/z 33-200 for full scan. The established HS-GC/MS method could be applied to analyze VGAs in the feces from human and rat appropriately. There are nine VFAs identified in the feces from human, and eight VFAs detected in the feces from rat by retrieving the NIST library, comparing with the standards and analyzing the MS data. Furthermore, the relative percentage contents of acetic acid, propionic acid and butyric acid accounted for roughly 85% of all VFAs by area normalization. The method is simple and sensitive, and it can be used to rapidly detect VFAs in the feces from human and rat.