Rapid bulk analysis using femtosecond laser ablation inductively coupled plasma time-of-flight mass spectrometry

Laser Ablation (LA) for direct solid sampling has advanced to provide accuracy and precision similar to that obtained using SN. Analytical performance metrics such as accuracy, precision, and limits of detection obtained when using femtosecond lasers are similar to those by SN. The reason for this improved performance is that the femtosecond laser produces essentially mono-disperse nanometer sized particles that are relatively easily digested in the ICP. In addition, the femtosecond laser material interaction is a photophysical process significantly reducing melting and elemental fractionation. A remaining aspect of ablation sampling is representative sampling; how much mass must be ablated to accurately analyze an inhomogeneous sample. The quantity of sample needed for bulk analysis is dependent on the inhomogeneity (or heterogeneity). Obviously, this same issue exists with sample digestion, and milligrams to grams of material are used to address this requirement. Laser ablation is beneficial in that only micrograms or less of sample are needed for the analysis. However, for bulk analysis of an inhomogeneous sample, the question is how much mass is required to adequately represent the bulk sample, and maintain the benefits of no sample digestion. The goal of this study was to demonstrate bulk analysis of a homogeneous and inhomogeneous sample by ablating large sample volumes using a high repetition rate (20 kHz) femtosecond pulsed laser. This approach is beneficial for bulk analysis of heterogeneous samples, for rapid analysis of difficult to dissolve samples, and for analyzing impurities over a large surface of homogeneous samples.