2008 MAR 24 - (VerticalNews.com) -- "The precision and accuracy of the U-238/Th-232 ratio were evaluated from liquid nebulization and direct solid sampling repetitive pulsed laser ablation. Nanosecond and femtosecond pulsed lasers at 266 nm wavelength were utilized for the ablation studies," researchers in the United States report.

  "The ICP-MS and sampling parameters were optimized for each procedure;. ow rates, gases, laser energy and other parameters were optimized for the particular sampling approach and therefore will not be the same. The work is not a comparison per se but represents performance metrics for three optimized sampling modalities. As expected, nanosecond pulsed ablation provided the greatest inaccuracy (>30%) from the nominal U-238/Th-232 bulk ratio. This deviation from bulk ratio is attributed to incomplete vaporization of large particle agglomerates produced by nanosecond laser ablation. Femtosecond pulsed ablation provided inaccuracy (similar to 1-3%) approaching that of liquid nebulization (similar to 1%). In terms of temporal relative standard deviation (TRSD) and relative standard deviation (RSD), liquid nebulization provided the best precision for the 238 U/ 232 Th ratio (TRSD similar to 3-5%, RSD similar to 0.2-0.6%), femtosecond laser ablation (TRSD similar to 5-12%, RSD similar to 1%) and nanosecond laser ablation (TRSD similar to 25-48%, RSD similar to 9-12%)," wrote J.J. Gonzalez and colleagues, University of California ...read more

  2008 MAR 24 - (VerticalNews.com) -- According to recent research from Bremen, Germany, "LA-ICP-MS analysis of the chemical composition of biogenic carbonate has many applications in the environmental sciences but the characteristics of the material produced by the ablation process are largely unknown. To fill this gap, we have undertaken a study of the chemical and physical nature of particles produced by laser ablation of biogenic carbonates. ...read more

  2008 MAR 24 - (VerticalNews.com) -- "A differential mobility analyzer (DMA) passes laser ablation (LA) particles and agglomerates within a narrow range of electrical mobilities to the inductively coupled plasma mass spectrometer (ICP-MS). No particle collection or offline particle analysis is required," scientists in the United States report.

  "Fractionation is assessed with the Cu+/Zn+ signal ratio. Results presented in this paper support previous findings that ns LA provides many small Zn-rich particles and some much larger Cu-rich particles and that fs LA produces large agglomerates of small particles. The composition of the aerosol produced by fs LA falls between the relatively Zn-rich and Cu-rich extremes of ns LA. Femtosecond LA provides elemental ratio measurements that remain more stable with respect to time, which allows a greater degree of confidence in LA results," wrote N.J. Saetveit and colleagues, Iowa State University ...read more