Trace element analysis by two-colour laser enhanced ionization spectroscopy in a graphite furnace

We demonstrate improved performance of laser enhanced ionization (LEI) with two-colour excitation in graphite furnace. With a modified electrode arrangement we have been able to measure LEI signals at atomization temperature of 2600°C without interference from the electric heating current. The sensitivity and selectivity are greatly improved when step-wise excitation is used instead of single photon LEI. Detection limits in the pg range are reported for five different elements. Futhermore we demonstrate and discuss how a simple and efficient correction for spectral interference can be performed in two-colour LEI.