The influence of cone orifice diameter on ion transmission in solution and laser ablation ICP-MS

Optimal sampler and skimmer cone orifice diameter has been well developed for solution based inductively coupled plasma-mass spectrometry (ICP-MS) but is not fully understood for modern laser ablation (LA) systems. This research investigates the impact of various cone orifice sets and the effect they have on ICP-MS sensitivity using solution mode and whilst using a low-dispersion LA system. A wide range of elements between the masses 7Li and 238U and their oxides have been measured via solution nebulisation as well as NIST 610 glass reference material and multi-elemental gelatine microdroplets via laser ablation. For multi-elemental micro droplets, 7 out of 11 elements analysed showed a statistically significant increase in sensitivity when a reduction of cone orifice size of 0.1 mm was used, compared to the standard cone orifice size. Similarly, for the ablation of NIST 610, 7 out of 11 elements displayed a statistically higher sensitivity with a 0.1 mm reduced orifice size. This analysis has confirmed suitability of standard cone sets for nebulisation of homogeneous solutions whilst suggesting a slight reduction in cone orifice diameter improves ion transmission through the cones towards the mass spectrometer by up to 272% (NIST 610) or 124% (multi-elemental droplets) for LA-ICP-MS.