Identification of Phylloquinone (Vitamin K1) as an Unknown Peak in Electron Capture Detection Gas Chromatograms of Pyrethroid Insecticide Residues

Abstract

An unknown peak was observed in spinach extract during routine analysis of 7 pyrethroid insecticides by gas chromatography with electron capture detection (GC-ECD) using a DB-1 column (20 m × 0.25 mm id, 0.1 μm film thickness). It eluted later than the 7 pyrethroids, and it was also found in other agricultural crops. The intensity of the unknown peak was related to the green color of the sample: It was absent in white vegetables such as radish root or onion. Data from GC/direct deposition/Fourier-transform infrared spectroscopy (FTIR) suggested it might be phylloquinone (vitamin K1). The identity was confirmed also by using electron impact capillary GC/mass spectrometry (MS). Although phylloquinone has no halogens, it showed very high sensitivity by ECD (63Ni), responding to 10 pg.