Investigation of plasmas produced by laser ablation using single and double pulses for food analysis demonstrated by probing potato skins

Abstract

We report on investigations of plasmas produced by laser ablation of fresh potatoes using infrared nanosecond laser radiation. A twin laser system consisting of two Nd:YAG oscillators was used to generate single or double pulses of adjustable interpulse delay. The potatoes were irradiated under ambient air with moderate pulse energies of about 10 mJ. The expansion dynamics of the ablation plume was characterized using fast imaging with a gated camera. In addition, time-resolved optical emission spectroscopy was applied to study the spectral line emission of the various plasma species. The electron density was deduced from Stark broadening, and the plasma temperature was inferred from the relative emission intensities of spectral lines. The relative concentrations of metals were estimated from the comparison of the measured emission spectra to the spectral radiance computed for a plasma in local thermal equilibrium. It is shown that the plasma produced by double pulses has a larger volume and a lower density. These properties lead to an increase of the signal-to-noise ratio by a factor of 2 and thus to an improved measurement sensitivity.

Determination of a brass alloy concentration composition using calibration-free laser-induced breakdown spectroscopy

“…It requires little or no sample preparation and LIBS has the capability of measuring most of chemical elements [1,[5][6][7]. In regards to these advantages, LIBS is widely applied across many fields, such as analysis of art works and cultural heritage conservation [8,9], industrial applications for material processing control [10][11][12][13], quality insurance environmental protection [14,15]; and in medical field such as analyzing toxic substances [16,17]. A LIBS module has been integrated by NASA and ESA for their planetary exploration rovers to analyze soil on the Mars [18][19][20].…”

Two-step procedure for trace element analysis in food via calibration-free laser-induced breakdown spectroscopy

“…Laser-induced breakdown spectroscopy (LIBS) stimulated strongly growing interest in the past years due to the capability of performing rapid multielemental analyses without or with minimized sample preparation [4,5]. Thus, the analytical capabilities of LIBS were investigated for various types of food such as wheat [6,7], cereals [8,9], vegetables [10,11], milk powder [12,13], and oil [14]. The presented approaches * Corresponding author: hermann@lp3.univ-mrs.fr that aim to quantify the elemental composition can be divided into three categories: (i) measurements based on calibration with standard samples; (ii) chemometric methods; (iii) calibration-free measurements.…”

“…In addition, the application of CF-LIBS to organic materials encounters a supplementary difficulty that arises from matrix elements C, H, O and N. According to the atomic structures including large energy gaps between the electronic excitation levels, equilibrium Boltzmann distributions are hardly achieved for these elements [25,26]. The matrix elements are therefore generally ignored and CF-LIBS measurements are limited to a partial analysis of the elemental composition of food [17,12,18,11,19]. In the present paper, we present a method that improves the sensitivity of CF-LIBS, enabling thus the quantification of the full elemental composition.…”

Laser-induced breakdown spectroscopy determination of K in biochar-based fertilizers in the presence of easily ionizable element

“…However, some strategies have been developed [6][7][8][9] to improve the detectability of LIBS, which include the use of a spark for sample pre-ablation [10,11], spatial confinement of laser-induced plasma [12][13][14], use of a micro torch [15] and use of two (double-pulse) or more lasers pulses for plasma species excitation [16][17][18][19][20]. Some authors attribute the observed increase in sensitivity to the increment of temperature and electronic density of the plasma, an higher sample mass ablation and plasma reheating [21][22][23][24][25][26][27].…”