Zheng Lina, Kulkarni Pramod, Birch M Eileen, Deye Gregory, Dionysiou Dionysios D
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health 4676 Columbia Parkway, MS R7 Cincinnati, OH, 45226.
Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH, 45221.
Aerosol Sci Technol. 2016 Aug 18;50(11):1155-1166. doi: 10.1080/02786826.2016.1224804.
A sensitive, field-portable microplasma spectroscopy method has been developed for real-time measurement of carbon nanomaterials. The method involves microconcentration of aerosol on a microelectrode tip for subsequent analysis for atomic carbon using laser-induced breakdown spectroscopy (LIBS) or spark emission spectroscopy (SES). The spark-induced microplasma was characterized by measuring the excitation temperature (15,000 - 35,000 K), electron density (1.0 × 10 - 2.2 × 10 cm), and spectral responses as functions of time and interelectrode distance. The system was calibrated and detection limits were determined for total atomic carbon (TAC) using a carbon emission line at 247.856 nm (C I) for various carbonaceous materials including sucrose, EDTA, caffeine, sodium carbonate, carbon black, and carbon nanotubes. The limit of detection for total atomic carbon was 1.61 ng, equivalent to 238 ng m when sampling at 1.5 L min for 5 min. To improve the selectivity for carbon nanomaterials, which consist of elemental carbon (EC), the cathode was heated to 300 °C to reduce the contribution of organic carbon to the total atomic carbon. Measurements of carbon nanotube aerosol at elevated electrode temperature showed improved selectivity to elemental carbon and compared well with the measurements from thermal optical method (NIOSH Method 5040). The study shows that the SES method to be an excellent candidate for development as a low-cost, hand-portable, real-time instrument for measurement of carbonaceous aerosols and nanomaterials.
已开发出一种灵敏、便于现场携带的微等离子体光谱法，用于实时测量碳纳米材料。该方法包括将气溶胶微浓缩在微电极尖端，随后使用激光诱导击穿光谱法（LIBS）或火花发射光谱法（SES）对原子碳进行分析。通过测量激发温度（15,000 - 35,000 K）、电子密度（1.0×10 - 2.2×10 cm）以及作为时间和电极间距离函数的光谱响应，对火花诱导的微等离子体进行了表征。使用247.856 nm（C I）处的碳发射线，针对包括蔗糖、乙二胺四乙酸、咖啡因、碳酸钠、炭黑和碳纳米管在内的各种含碳材料，对该系统进行了校准并确定了总原子碳（TAC）的检测限。总原子碳的检测限为1.61 ng，相当于在1.5 L/min采样5分钟时的238 ng/m³。为提高对由元素碳（EC）组成的碳纳米材料的选择性，将阴极加热至300°C以减少有机碳对总原子碳的贡献。在升高的电极温度下对碳纳米管气溶胶的测量显示出对元素碳的选择性提高，并且与热光学法（NIOSH方法5040）的测量结果相当。该研究表明，SES方法是开发低成本、便于携带的实时测量含碳气溶胶和纳米材料仪器的极佳候选方法。
