Analysis of Organic Powder Samples by Using the Metal-Assisted Subtarget Effect in a Transversely-Excited Atmospheric (TEA) CO2 Laser-Induced He Gas Plasma at 1 atm

A novel technique for analysis of organic powder samples has been developed utilizing a metal subtarget-assisted gas plasma induced by using a TEA CO2 laser under He gas at atmospheric pressure. In this technique, the sample was filled in a hole (diameter of 8 mm and thickness of 2 mm) made of plastic plate (10 mm × 10 mm × 2 mm). The plastic holder filled with the sample was then sandwiched between two Cu plates (25 mm × 25 mm × 0.3 mm). One Cu plate, which had a hole with a diameter of 2.5 mm, functions to suppress the blowing-off of the sample, and the other served as a subtarget. When the TEA CO2 laser (1.5 J, 10.6 μm) was successively irradiated onto the sample’s surface passing through the hole of the Cu plate, a hole (2.5 mm in diameter and 2 mm in depth) was produced inside the sample, and the laser beam directly impinged on the subtarget. Once the laser beam had struck the subtarget, a strong subtarget-assisted gas plasma was induced. The initial gas plasma was confined in the hole region, and in later stage, the gas plasma expanded with a hemispherical shape (diameter of 1 cm). The fine particles of the sample were vaporized and effectively dissociated and atomized in the hole, and the atoms moved to the hemispherical plasma region to be excited through He meta-stable atoms. Using this method, an excellent linear calibration curve with zero intercept was made using a herb medicine containing different concentrations of Cr. The detection limits of Cr and Pb in the herb medicine were around 1 and 5 mg/kg, respectively. KCI Citation Count: 9