Direct analysis of powder samples using transversely excited atmospheric CO2 laser-induced gas plasma at 1 atm

Abstract

A novel method for the direct and sensitive analysis of powder samples has been developed by utilizing the characteristics of a transversely excited atmospheric (TEA) CO(2) laser. In this study, a powder sample was placed in a container and covered by a metal mesh; the metal mesh functions to control the blowing-off of the powder. The container was then perpendicularly attached on a metal surface. When a TEA CO(2) laser (1.5 J, 200 ns) was focused on the metal surface, a large hemispherical gas plasma (radius of around 8 mm) with long emission lifetime (several tens of microseconds) was produced without ablating the metal surface. The high-speed expansion force of the gas plasma samples the powder covered by the metal mesh and fine powder particles are sent into the gas plasma region to be dissociated and excited. Sensitive semi-quantitative analysis was made on organic powder samples such as powdered rice, starch, seaweed (agar), and supplements. The detection limit of heavy metals of Cr in powdered mineral supplement was approximately 0.55 mg/kg.

Particle formation by infrared laser ablation of MALDI matrix compounds

“…For spectroscopic applications, IR lasers can be used for LIBS either alone or in combination with IR or UV lasers in double‐pulse experiments . In laser ablation inductively coupled plasma mass spectrometry, IR ablation can be useful in some applications, for example, the analysis of samples in powder form; however, there has been a general move from IR to UV in geochemistry because of better bond‐breaking characteristics of UV lasers . IR lasers have been used for MALDI but have seen limited application because of difficulties in controlling the quantity of material removed with ionization under vacuum .…”

Development of Plasma Source Sustained by Semiconductor Microwaves

“…[19][20][21][22][23] Another powder fixation method uses supporting tape, 24,25 but methods that do not require pretreatment are preferred for in situ and on-site monitoring in industry. Pedarnig et al and Kagawa et al developed unique powder analysis systems without pretreatment requirements, 26,27 but these still require special equipment that is inconvenient for in situ powder analysis. Due to the small volume of laser-induced plasma, LIBS powder samples should be homogeneous, such as alloys or well-mixed powders; this method is not well suited for heterogeneous samples.…”

A novel specimen-preparing method using epoxy resin as binding material for LIBS analysis of powder samples

“…The crater in the epoxy resin was in a more regular shape with a crater diameter of 762 μm, smaller than the 853 μm of pellet sample. In addition, the crater of pellet sample showed a notable increasing in depth towards the center, attributed to the melted material being pushed out of the interaction region by the pressure of the laser pulse and accompanied shock wave [14,16], while the crater in the resin possessed a relatively flat bottom, owing to the greater cohesiveness and mechanical strength of the latter. Similarly, in the case of epoxy resin samples, the crater displayed an incremental depth and relatively constant diameter with the increasing ablation number compared to distinct expansion for the crater in pellet sample.…”

“…On the other hand, the addition of the binder affects the homogeneity of the sample in the way called the "Brazil nut effect", and particles of different sizes could result in the longitudinal inhomogeneity while being mixed, as the larger particles always go upward and the smaller ones go downward [13]. That is to say, to obtain analytical results with acceptable accuracy and precision, binders with greater hardness, adhesiveness and homogeneity are in urgent demand [14].…”