Sensitivity enhancement in laser ablation ICP-MS using small amounts of hydrogen in the carrier gas

The addition of 4 - 9 ml min(-1) of hydrogen to the helium carrier gas flow in 193 nm excimer laser ablation increases the sensitivity for most of 47 investigated elements by a factor of 2 - 4. The sensitivity enhancement for some elements, including beryllium, phosphorus, arsenic, platinum and gold, is even 5 - 7 fold. This effect can be explained by a higher electron temperature in the plasma. A correlation exists between the enhancement factor and the 1st ionization energy. Limits of detection are improved for all elements except those with hydrogen based polyatomic interferences, such as silicon, potassium, calcium and selenium, thus opening up new applications in LA- ICP- MS. A similar but weaker effect was found for the addition of methane; almost no sensitivity enhancement was found for nitrogen addition.