A calibration strategy for LA-ICP-MS analysis employing aqueous standards having modified absorption coefficients

Laser ablation ICP-MS is a powerful technique for the direct elemental anal ysis of solids with spatial resolution down to a few microns. However, its range of application is limited by the lack of calibration standards. This paper describes a novel approach to calibration that employs aqueous standa rds whose absorption coefficients are modified, by the addition of a chromo phore, to produce the desired ablation yield. Chromophores for the importan t laser wavelengths at 193, 248 and 266 nm are given. The mechanism of abla tion and parametric dependences for the modified aqueous standards were inv estigated and it was concluded that ablation proceeds by a three step proce ss leading ultimately to nebulisation of the bulk liquid. This is important as such a process should not involve fractionation between elements. Calib ration curves produced using the aqueous standards were linear and reproduc ible, but internal standardisation is required to provide linked calibratio n for real samples. NIST standard Reference Material 613 Trace Elements in Glass and low density polyethylene were analysed and the results agreed wit h reference values or those obtained by other techniques.