Optical emission analysis of solid samples by decoupled sputtering/excitation using a low fluence laser synchronized with a pulsed glow discharge

The use of a microsecond-pulsed glow discharge, synchronized with an ablation laser operating under breakdown fluence, assists in the excitation of the ablated material generated during the analysis. With the glow discharge operating in pulsed mode, it is possible to synchronize accurately both sources to maximize the signal. Additionally, both sources can be independently adjusted to optimize the sample removal and its excitation. By means of the decoupling approach, typical laser energies required for detectable emission signals can effectively be lowered below the excitation and ionization thresholds of the analyte to those required solely for ablation of the sample surface. Under these conditions, the laser represents an advantageous mode to transform solid samples into gas phase that will be efficiently excited by the glow discharge. The advantage of the combination of the techniques has been demonstrated in alloyed samples (Cr/Fe and brass) where a net enhancement in the analytes signals even under sub-threshold and sub-sputtering conditions occur.