100% Efficient Sub-Nanoliter Sample Introduction in Laser-Induced Breakdown Spectroscopy and Inductively Coupled Plasma Spectrometry: Implications for Ultralow Sample Volumes

Abstract

Recently, nanoflow nebulizers with low-volume drain-free spray chambers became available for inductively coupled plasma-mass spectrometry application for analysis of very small sampling volumes. The present technical note reports on a different approach for 100% efficient subnanoliter sample introduction, the application of monodisperse piezoelectric microdroplet dispensers which generate 40-50 microm droplets with high reproducibility if nozzles of 30 microm diameter are applied. The droplets having volumes below 0.1 nL can be introduced loss-free and without plasma loading, with frequencies up to approximately 100 Hz into analytical plasmas. In this technical note, the analytical figures of merit of laser-induced breakdown spectroscopy and inductively coupled plasma-optical emission spectrometry with single droplet introduction are reported using Ca and Au standard solutions as examples. Future engineering is required to reduce the total sample volumes from the relatively large sample reservoir of the current study, thereby reducing potential issues of washout while enabling analysis of ultralow total sample volumes.

Optimization of chemical and instrumental parameters in hydride generation laser-induced breakdown spectrometry for the determination of arsenic, antimony, lead and germanium in aqueous samples

“…Some approaches to overcome difficulties encountered in bulk liquid analysis include plasma formation: on flowing-jet liquid [12,13], on the surface of the liquid [14,15], on single isolated droplets [16] and in cavitation bubbles [17]. Alternative to single-pulse LIBS experiments, doublepulse LIBS technique [18,19] has been successfully applied for the analysis of aqueous [20] and underwater [21] samples in which the first laser pulse is used to create a gaseous atmosphere and the second pulse produce plasma with reduced background emission and longer lifetimes.…”

Multi-element model for the simulation of inductively coupled plasmas: Effects of helium addition to the central gas stream

“…This is a crucial application for environmental analysis (particulate matter) and also because more and more nano-particles are produced for various applications in industry or medicine and hence, need to be analysed as well. Furthermore, new sample introduction systems are under investigation to apply minimal amounts of analyte at high efficiency to the ICP [5,6]. Another approach for further improvement of ICPs is to use new kinds of torches which only require a small amount of argon compared to usual torches [7][8][9].…”

LIBS Analysis of Liquids and of Materials Inside Liquids

“…8.9). Among the application of LIBS on a liquid surface there are: rapid analysis of the pharmaceutical formulation [6] and water contamination [7,8]; studies for medicine [9], and chemical analysis of very limited sample volumes [10,11], particularly important for bio-medical and forensic applications. LIBS measurements of bulk liquids might be employed for in situ detection of leakages in industrial and power plants [1,12,13], other kinds of water contamination [14,15], geothermal winds in deep oceans [16], and direct analysis of liquids inside transparent containers [6].…”

“…Differently, LIBS analysis of single liquid droplets deal with volumes in order of only 0.1 nL and this is important when availability of the sample is limited. By LIBS the absolute detection limit of 23 fg of Ca was achieved per droplet of 50 lm diameter (65 pL), while averaging over more droplets reduces this limit to 3.3 fg [11]. Well controlled analyte volume might be obtained by commercial micro-droplet dispensers, which deliver a few hundred droplets per second.…”

“…Consequently, the droplet itself additionally increases the laser energy density in direction of the beam propagation. The breakdown probably initiates on the back droplet side and later propagates towards the laser, vaporizing the whole liquid volume [11]. Finite timescales of heat and mass transfer play an important role both in droplet and particle vaporization.…”