Electrothermal atomization analysis time

FFF-ICP-MS The ICP-MS is a multielement analysis tool ideally suited for direct coupling with FFF. The ICP torch is capable of vaporizing and ionizing particles in the eluent up to 10 pm, and the plasma is then fed into an MS for simultaneous detection of many elements. Quadripole, mass-sector, and time of flight MSs are now available, depending on the sensitivity, mass resolution, and response time required. FFF-ICP-MS yields element-based size distributions. Other element detection systems that have been used include ICP-AESs, electrothermal atomic absorption spectrometers, and very recently laser-induced breakdown spectrometers. 

Atomic absorption spectrometry (AAS) was established as the most popular gas chromatography (GC) detection technique for lead speciation analysis in the first years of speciation studies. The increase of the residence time of the species in the flame using a ceramic tube inside the flame and, later, the use of electrically heated tubes, made out of graphite or quartz where electrothermal atomization was achieved, provided lower detection limits but still not sufficiently low. Later, the boom of plasma detectors, mainly microwave induced plasma atomic emission (MIP-AES) and, above all, inductively coupled plasma atomic emission and mass spectrometry (ICP-AES and ICP-MS, respectively) allowed the sensitivity requirements for reliable organolead speciation analysis in environmental and biological samples (typically subfemtogram levels) to be achieved. These sensitivity requirements makes speciation analysis of organolead compounds by molecular detection techniques such as electrospray mass spectrometry (ES-MS) a very difficult task and, therefore, the number of applications in the literature is very limited. 

The laser-enhanced ionization (LEI) technique or elemental mass spectrometry may be used to directly measure elemental ions. In LEI, a laser beam is used to excite the analyte atoms in either a flame or electrothermal atomizer cell. These atom cells are selected for LEI experiments because of their inherently low background ion population (in contrast to plasma sources, which are rich in ions). The laser-excited atoms undergo collisional processes that will ultimately lead to ionization of the analyte atoms. The ions are then collected and measured against a background current. Although extremely sensitive, the LEI technique is limited to detection of one analyte at a time in a flame or ETV atom cell. There are currently no commercial instruments available for LEI analysis. 

Flameless atomic absorption using an electrothermal atomiser is essentially a non-routine technique requiring specialist expertise. It is slower than flame analysis only 10—20 samples can be analysed in an hour furthermore, the precision is poorer (1—10%) than that for conventional flame atomic absorption (1%). The main advantage of the method, however, is its superior sensitivity for any metal the sensitivity is 100—1000 times greater when measured by the flameless as opposed to the flame technique. For this reason flameless atomic absorption is employed in the analysis of water samples where the flame techniques have insufficient sensitivity. An example of this is with the elements barium, beryllium, chromium, cobalt, copper, manganese, nickel and vanadium, all of which are required for public health reasons to be measured in raw and potable waters (section I.B). Because these elements are generally at the lOOjugl-1 level and less in water, their concentration is below the detection limit when determined by flame atomic absorption as a result, an electrothermal atomisation (ETA) technique is often employed for their determination. 

Atomic absorption spectrometry has been applied to the analysis of over sixty elements. The technique combines speed, simplicity and versatility and has been applied to a very wide range of non-ferrous metal analyses. This review presents a cross section of applications. For the majority of applications flame atomisation is employed but where sensitivity is inadequate using direct aspiration of the sample solution a number of methods using a preconcentration stage have been described. Non-flame atomisation methods have been extensively applied to the analysis of ultra-trace levels of impurities in non-ferrous metals. The application of electrothermal atomisation, particularly to nickel-based alloys has enabled the determination of sub-part per million levels of impurities to be carried out in a fraction of the time required for the chemical separation and flame atomisation techniques. 

Flame and electrothermal techniques Both atomic absorption and emission have been used, with the former most widely applied to the analysis of minor soil components. Detection limits can often be very similar to the concentration found in extraction solutions of natural soils. While the sampling procedure is easily automated, AAS, it is inefficient (both time and sample volume) for routine multielement... 

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