New Technique for the Direct Analysis of Food Powders Confined in a Small Hole Using Transversely Excited Atmospheric CO₂ Laser-Induced Gas Plasma

Abstract

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

Enhancement of carbon detection sensitivity in laser induced breakdown spectroscopy with low pressure ambient helium gas

“…These excited He atoms were shown to provide the He assisted excitation (HAE) mechanism for the delayed excitation and emission of the ablated analyte atoms when the plasma becomes relatively cooled and free from the charged particles [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The benefits of using ambient He gas in LIBS applications have been amply demonstrated in a number of cases according to our previous works, [15][16][17][18][19][20][21][22][23][24][25][26][27][28] including C analysis of steel products [29][30]. Nevertheless its application to C analysis of stones has yet to appear in the literature.…”

Comparative study of Nd:YAG laser-induced breakdown spectroscopy and transversely excited atmospheric CO2 laser-induced gas plasma spectroscopy on chromated copper arsenate preservative-treated wood

“…Thus, we expected that the TEA CO 2 laser might be used for wood analysis because the wood sample has high absorbance in the TEA CO 2 laser wavelength. However, as we reported in our previous work [13], the TEA CO 2 laser could not be used to generate plasma when the laser was directly focused on a soft sample. In order to generate plasma on a soft sample using the TEA CO 2 laser, we have developed a metal-assisted gas plasma technique.…”

“…The experimental setup used in this study was similar to that used in our previous work [13]. A pulsed TEA CO 2 laser (Shibuya SQ 2000 laser, pulse energy of 3 J, wavelength of 10.6 μm, pulse duration of 200 ns at full width half maximum, beam cross section of 3 mm × 3 mm) commercially produced by Shibuya Company for laser marking was used as an energy source for laser plasma generation.…”

LIBS Analysis of Geomaterials: Comparative Study of Basalt Plasma Induced by TEA CO2 and Nd:YAG Laser in Air at Atmospheric Pressure

“…The optical emission from the plasma was viewed in the direction parallel to the target surface (Figure 1(a)). A timeintegrated space-resolved laser-induced plasma spectroscopy (TISR-LIPS) was applied [12,[20][21][22][23]. Spatial resolution was achieved by changing the position of the plasma along the direction of the incoming laser beam.…”