Analysis of Impurities of Bacterium Source of Standard Endotoxin by Gas Chromatography/Mass Spectrometry

In order to analyse the impurity of bacterium source of standard endotoxin, 3-hydroxy fatty acid species in different standard endotoxins was determined by gas chromatography/mass spectrometry (GC/MS) using N,O- bis(trimethylsilyl) trifluoroacetamide as the silanizing reagent. GC/MS analysis was performed using a gas chromatograph equipped with a 60 m ×0.25 mm i.d. DB-5 fused silica capillary column and an injector at 250 °C. Helium was used as the carrier gas under a constant pressure of 206 kPa. The oven was programmed at a rate of 5 °C/min from 90 °C (held for 5 min) to 280 °C (held for 5 min). The sample size was 1 μL. The transfer line was maintained at 280 °C. The quadrupole mass spectrometer was operated in electron impact (EI) ionization mode, and the temperature of the source was maintained at 250 °C. The kind of 3-hydroxy fatty acids in 9000 EU/tube National Standard Endotoxin, 20 EU/tube Working Standard Endotoxin, Escherichia coli, Pseudomonas aeruginosa and deionized water were determined to study the purity of bacterium source of the standard endotoxin. It was shown that 9000 EU/tube National Standard Endotoxin and Escherichia coli only contained 3-hydroxytetradecanoic acid. There was 3-hydroxydodecanoic acid in 20 EU/tube Working Standard Endotoxin, which indicated the presence of impurity of bacterium source.