  Increasing the spatial resolution of Laser Ablation Inductively Coupled
Plasma Mass Spectrometry (LA-ICP-MS) is a challenge in microanalysis of
geological samples. Smaller sizes for the laser beam will allow for (1) high
resolution determination of trace element compositions, (2) accurate estimation
of crystal/melt partition coefficients, (3) detailed characterization of
diffusion profiles, and (4) analysis of fine volcanic glasses. Here, we report
about the figures of merit for LA-ICP Quadrupole MS down to a spatial
resolution of 5 {\mu}m. This study highlights the possibility to achieve
suitable limits of detection, accuracy and precision for geological samples
even at spatial resolutions of the order of 5 {\mu}m. At a beam size of 15
{\mu}m precision (measured as one sigma) and accuracy (expressed as relative
deviation from the reference value) are of the order of 10%. At a smaller beam
size of 8um, precision decreases to 15% for concentration above 1.7 {\mu}g g-1.
As the beam size is decreased to ~5 {\mu}m, precision declines to about 15% and
20% for concentrations above 10 {\mu}g g-1 using 42Ca and 29Si as internal
standard, respectively. Accuracy is better or equal to 10% and 13 % at beam
sizes of 15 and 10 {\mu}m respectively. When the spatial resolution is
increased to 8 {\mu}m, accuracy remains better than 15% and 20% for 42Ca and
29Si as internal standard, respectively. We employed such high-resolution
techniques to volcanic glasses in ash particles of the 2010 Eyjafjallaj\"okull
eruption. Our results are well consistent with the previously reported data
obtained at lower spatial resolution, supporting the reliability of the method.
