Rapid determination of ethylene oxide with fiber-packed sample preparation needle

Abstract

Fiber-packed sample preparation device was applied to the simultaneous derivatization/preconcentration of ethylene oxide (EO) in air samples. The polymer-coated filaments were packed longitudinally into the needle, and hydrogen bromide (HBr) was loaded onto the filaments in the preconditioning process. Simultaneous derivatization with HBr in the needle was made during the sampling process of the gaseous EO, and the corresponding derivatized analyte, 2-bromoethanol, was desorbed by passing a small amount of methanol through the extraction needle in the heated gas chromatograph (GC) injector. The basic extraction/desorption parameters for EO have been evaluated. The limit of detection (LOD), limit of quantification (LOQ) and the relative standard deviation (RSD) of run-to-run repeatability were 1.8 ng/L, 5.4 ng/L and less than 4%, respectively, with an extraction time of about 10 min. Satisfactory storage performance for three days at room temperature was also confirmed.

Introduction

Ethylene oxide (EO) is primarily used as an intermediate in the industrial process for the production of such as ethylene glycol. EO also employed in the sterilization of medical items. Exposure to EO causes an irritation of the nose and throat, dizziness, headache and vomiting. The potential carcinogenic activity has also been reported in the systematic studies for the human risk. According to the US Occupational Safety and Health Administration (OSHA), the permissible concentrations in the working place were 1 (v/v) ppm, corresponds to 1.8 μg/L, measured as an 8-h time weighted average (TWA) in 1984 [1], and 9.0 μg/L short-term excursion [2].

Due to high volatility and reactivity of EO, the stabilization should be carried out prior to the analysis for the accurate and sensitive determination of EO. Several methods have been developed for the determination of EO in air samples. Active charcoal coated with hydrogen bromide (HBr) has been widely used in the standard method [3], [4], [5], [6], [7]. EO can react with HBr to form 2-bromoethanol at room temperature. The method was recommended by both OSHA and the US National Institute for Occupational Safety and Health (NIOSH) [8]. This standardized method has a high sensitivity, however, the method is relatively complicated and time consuming.

The development of miniaturized sample preparation has been one of the most important fields in analytical chemistry due to the ecological and economical features such as rapid analysis with low operation cost and solvent consumption. In order to increase the extraction efficiency and reduce the volume of the required solvent, novel miniaturized sample preparation has been developed based on the solid-phase microextraction (SPME) technique [9], [10]. SPME was also employed for the determination of gaseous EO with TWA sampler [11], [12]. SPME has some advantages over conventional extraction techniques, such as simple, rapid and solvent less, however, it requires careful handling during the extraction and desorption processes.

The use of synthetic fibers as an extraction medium has also been studied in capillary electrophoresis (CE) [13], capillary electrochromatography (CEC) [14] and liquid chromatography (LC) [15], [16], [17], [18], and further applications of fibrous materials to the stationary phase have been reported [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]. In fiber-in-tube solid-phase extraction (FIT-SPE), several hundreds of the polymeric filaments were packed longitudinally into a capillary of either polyether ether ketone (PEEK) or polytetrafluoroethylene (PTFE) [15], [16], [17]. Using the FIT-SPE technique, trace amount of analytes could be extracted onto the surfaces of the fine filaments by simply passing an aqueous sample solution. The extracted analytes were desorbed by pumping through a small amount of solvent as the extraction tube. Qi et al. developed a polymer nanofibers and packed into a section of pipette tip as a extraction sorbent for aromatic pollutants in environmental water [18]. The synthetic fiber was also developed for the extraction medium in gas chromatographic (GC) analysis [30], [31], [32], [33], [34].

As an alternative miniaturized sample preparation technique, several needle-type sample preparation devices have been studied for the GC analysis of volatile organic compounds (VOCs) [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43]. With the needle extraction technique, various applications to the determination of VOCs were reported, because a wide variety of the extraction media could be packed into the needle. Compared to the SPME technique, needle-type sample preparation technique is relatively robust and rapid sample preparation method. Furthermore, needle-type extraction device can introduce all of the extracted analytes into the GC, allowing low limit of quantification (LOQ) with small amount of sampling volume. Our previous studies revealed that a fiber-packed needle-type extractor has been successfully applied to the simultaneous derivatization/preconcentration of volatile aldehydes in air samples [31], [32], [34].

In this work, a fiber-packed needle was introduced as the sample preparation device for gaseous EO. The method is based on derivatization with HBr aqueous solution during the sampling of gaseous EO samples. The extraction/desorption power of the fiber-packed needle was studied along with the evaluation of the storage performance of the needle device for the extracted 2-bromoethanol under the room temperature. The method was also applied to the analysis of tobacco smoke and automobile exhaust to confirm the extraction performance of EO from complex sample mixtures.