Flames laser enhanced ionization spectrometry

Fig. 127. Flame laser enhanced ionization spectrometry [670, 671]. (a) Flashlamp/dye laser, (b) high voltage, (c) trigger photodiode, (d) preamplifier, (e) pulse amplifier, (f) active filter, (g) boxcar averager, (h) chart recorder. (Reprinted with permission from Ref. [671]).

Figure 50. Flame laser-enhanced ionization spectrometry (0)...

O. Axner, I. Lindgren, I. Magnusson, H. Rubinsztein-Dunlop Trace element determination in flames by laser-enhanced ionization spectrometry. Anal. Chem. 57, 773 (1985)... 

O. Axner, I. Magnusson, J. Petersson, S. Sjostrom Investigation of the multielement capability of laser-enhanced ionization spectrometry in flames for analysis of trace elements in water solution. Appl. Spectr. 41,19 (1987)... 

Laser-enhanced ionization (LEI) is one of a family of laser-induced ionization techniques which have been exploited for analytical spectrometry. The laser-induced ionization schemes which are important for flame spectrometry are illustrated in Fig. 1. 

Sources for atomic spectrometry include flames, arcs, sparks, low-pressure discharges, lasers as well as dc, high-frequency and microwave plasma discharges at reduced and atmospheric pressure (Fig. 5) [28], They can be characterized as listed in Table 2. Flames are in thermal equilibrium. Their temperatures, however, at the highest are 2800 K. As this is far below the norm temperature of most elemental lines, flames only have limited importance for atomic emission spectrometry, but they are excellent atom reservoirs for atomic absorption and atomic fluorescence spectrometry as well as for laser enhanced ionization work. Arcs and sparks are... 

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. 

---