Simultaneous Determination of Benzene and Toluene in Pesticide Emulsifiable Concentrate by Headspace GC-MS

The toxic inert ingredients in pesticide formulations are strictly regulated in many countries. In this paper, a simple and efficient headspace-gas chromatography-mass spectrometry (HSGC-MS) method using fluorobenzene as an internal standard (IS) for rapid simultaneous determination of benzene and toluene in pesticide emulsifiable concentrate (EC) was established. The headspace and GC-MS conditions were investigated and developed. A nonpolar fused silica Rtx-5 capillary column ( i.d. and 0.25？μm film thickness) with temperature programming was used. Under optimized headspace conditions, equilibration temperature of 120°C, equilibration time of 5？min, and sample size of 50？μL, the regression of the peak area ratios of benzene and toluene to IS on the concentrations of analytes fitted a linear relationship well at the concentration levels ranging from 3.2？g/L to 16.0？g/L. Standard additions of benzene and toluene to blank different matrix solutions 1ead to recoveries of 100.1%–109.5% with a relative standard deviation (RSD) of 0.3%–8.1%. The method presented here stands out as simple and easily applicable, which provides a way for the determination of toxic volatile adjuvant in liquid pesticide formulations. 1. Introduction Emulsifiable concentrate (EC) formulations, which are the blend of active ingredient, organic solvent, and surfactants, are the major pesticide formulations currently used in many developing countries. Compared to other formulations, advantages of EC include higher concentration of active ingredient and being simple to manufacture and low in cost, relatively easy to handle, transport, and store, not abrasive, and uniformly spreading and wetting under normal spray and weather conditions. However, the disadvantages of EC cannot be overlooked. The large amount of the organic solvent makes the EC formulations flammable and corrosive. More seriously, the hidden toxic inert ingredients in EC, such as benzene and toluene, might cause adverse effects to humans and the environment. Benzene and toluene are ubiquitous environmental pollutants. The American Petroleum Institute (API) stated in 1948 that “it is generally considered that the only absolutely safe concentration for benzene is zero” [1]. The International Agency for Research on Cancer (IARC) rated benzene as “known to be carcinogenic to humans” (group 1) [2]. Although toluene is less toxic than benzene, inhaling high levels of toluene in a short time may cause lightheadedness, nausea, or sleepiness. It can also cause unconsciousness and even death. In order to reduce the potential risk