ETAAS sample introduction

One of the advantages of ETAAS is that it is fiee from transport interferences because usually no nebulizers are used for sample introduction. A measured volume of sample is deposited on the platform in the atomizer by an autosampler, so that sample viscosity and other physical parameters do not play a significant role. The major sources of errors in ETAAS are loss of the analyte element by volatilization in the pyrolysis stage prior to atomization and the formation of stable compounds with concomitants in the gas phase. 

Similar to FI systems, in-line coupling of a sequential injection network with suitable detectors renders a detailed insight into leaching kinetics. As a consequence of the discontinuous flow nature of SIA, the in-line hyphenation of microcolumn assays with ETAAS is relatively simple, because of the discrete, noncontinuous operation of the detector. On the other hand, interfacing the miniaturized flow assembly with continuously operating detectors such as FAAS, HG-AFS, ICP-AES and ICP-MS requires the incorporation of conventional sample injectors (e.g., solenoid valves, rotary valves) for discrete introduction into the detection instrument of metered leachate volumes. 

Sample dissolution for ETAAS is preferably done using HNO3 or HNO3-H2O2. The method does not tolerate presence of perchloric and hydrofluoric acids. The presence of other acids in the final digests should also be avoided. Otherwise interferences may appear, sensitivity is reduced as well as the lifetime of the atomizer is shortened. Therefore the introduction of solid samples has been an object of permanent interest in ETAAS. 

In contrast to FAAS not only liquid but also solid samples can be analyzed in ETAAS. However, one of the problems is the reliable introduction of solid samples into the atomizer. The high sensitivity of the technique makes it necessary to handle samples in the submilligram range. The most reliable procedure was shown to be the slurry technique [14] whereby a finely powdered and/or homogenized solid sample is kept in suspension by ultrasonic agitation so that it can be introduced into the atomizer with a conventional autosampler. This technique has the significant advantage that a solid sample can be treated like a liquid, i.e., it can not only be pipetted but can also be diluted, mixed with a modifier, and several aliquots can be taken reproducibly. 

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