ABSTRACT
It is recognized that standard ICP-MS instrumentation using a traditional sample introduction system comprising a spray chamber and nebulizer has certain limitations, particularly when it comes to the analysis of complex samples. Some of these known limitations include the following:
Inability to analyze solids.• Contamination issues with samples requiring multiple sample preparation • steps. Liquid aerosol can impact ionization process.• Total dissolved solids must be kept below 0.2%.• If matrix has to be removed, it has to be done offline.• Long washout times required for samples with a heavy matrix.• Dilutions and addition of internal standards can be labor intensive and time • consuming. Matrix components can generate severe spectral overlaps on many analytes.• The analysis of slurries is very difficult.• Matrix suppression can be quite severe with some samples.• Spectral interferences generated by solvent-induced species can limit detec-• tion capability. Organic solvents can present unique problems.• Sample throughput is limited by the sample introduction process.• Not suitable for the determination of elemental species or oxidation states.•
Such were the demands of real-world users to overcome these kinds of problem areas that instrument manufacturers devised different strategies based on the type of samples being analyzed. Some of these strategies involved parameter optimization or modification of instrument components, but it was clear that this approach alone was not going to solve every conceivable problem. For this reason, they turned
their attention to the development of sampling accessories, which were optimized for a particular application problem or sample type. Over the past 10-15 years, this demand has led to the commercialization of specialized sample introduction tools, not only by the instrument manufacturers themselves, but also by third-party vendors specializing in these kinds of accessories. The most common ones used today include the following:
Laser ablation systems (LA)• Flow injection analyzers (FIA)• Electrothermal vaporizors (ETV)• Chilled spray chambers and desolvation systems• Direct injection nebulizers (DIN)• Fast automated sampling procedures• Chromatographic separation equipment•
Let us now take a closer look at some of these techniques to understand their basic principles and what benefits they bring to ICP-MS.
