On-line sample pre-treatment systems interfaced to electrothermal atomic absorption spectrometry

Atomic spectrometric techniques working with a continuous supply of sample, such as flame atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry, are well suited for on-line connection through flow injection arrangements. For the determination of elements at lower concentrations, electrothermal atomization is often needed owing to the requirement for better detection limits, However, connecting a batch technique such as electrothermal atomic absorption spectrometry to a continuous flow or a flow injection system presents some fundamental difficulties, making it a real challenge for the analytical chemist to design suitable interfaces, There are different ways of interfacing the systems to each other; the available versions utilize either on-line sample treatment with off-line measurement or are completely on-line arrangements. Complex samples cannot be directly processed by this technique owing to severe matrix interferences, which have not been minimized despite the development of efficient background correction devices. Successful matrix separation can be achieved on-line through solvent and sorbent extraction, precipitation and coprecipitation, volatile compound generation and liquid chromatography. Moreover, transformation of the sample and/or its fractions into a form that can be analyzed in a graphite furnace often requires unpleasant, tedious and time-consuming digestion procedures. Microwave heating has emerged as a means of dramatically improving leaching, mineralization or digestion processes and has frequently been used with in-batch or on-line systems, This paper outlines the most recent advances in the development of flow injection-graphite furnace interfaces and also describes the on-line sample pre-treatment systems developed so far for electrothermal atomic absorption detection.