Ultra-micro analysis of liquids and suspensions based on laser-induced plasma emissions

Nai Ho CHEUNG*, C. W. Ng, W. F. Ho, E. S. Yeung

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

15 Citations (Scopus)


Spectrochemical analysis of liquids and suspensions using laser-induced plasma emissions was investigated. Nd:YAG pulsed-laser (532-nm) ablation of aqueous samples produced plasmas that were hot (few eV) and extensively ionized, with electron density in the 10 18 cm -3 range. Analyte line signals were initially masked by intense plasma continuum emissions, and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower (< 1 eV) temperature but comparable electron density. The plasma continuum emissions were relatively weak and the signal-to-back-ground ratio was a thousand times better. This 'cold' plasma was ideal for sampling trace amounts of biologically important elements such as sodium and potassium. By ablating hydrodynamically focused jets in a sheath-flow, and with acoustic normalization for improved precision, the single-shot detection limits of sodium and potassium were 8 and 50 fg, respectively. Using the sheath-flow arrangement, the amounts of sodium and potassium inside single human red blood cells were simultaneously determined for the first time. The intracellular contents for a given blood donor were found to vary significantly, with only very weak correlation between the amounts of sodium and potassium in individual cells.

Original languageEnglish
Pages (from-to)274-277
Number of pages4
JournalApplied Surface Science
Publication statusPublished - May 1998

Scopus Subject Areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

User-Defined Keywords

  • Laser-induced plasma
  • Pulsed-laser ablation
  • Single cell analysis
  • Spectrochemical analysis of liquids and suspensions


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