LAMMA instruments

In Laser Ionization Mass Spectrometry (LIMS, also LAMMA, LAMMS, and LIMA), a vacuum-compatible solid sample is irradiated with short pulses ("10 ns) of ultraviolet laser light. The laser pulse vaporizes a microvolume of material, and a fraction of the vaporized species are ionized and accelerated into a time-of-flight mass spectrometer which measures the signal intensity of the mass-separated ions. The instrument acquires a complete mass spectrum, typically covering the range 0— 250 atomic mass units (amu), with each laser pulse. A survey analysis of the material is performed in this way. The relative intensities of the signals can be converted to concentrations with the use of appropriate standards, and quantitative or semi-quantitative analyses are possible with the use of such standards. 

Odom and Schueler (1990) describe the basic components of the instrument, known as LIMA 2A or LAMMA 1000, depending upon the particular manufacturer. Figure 3.11 illustrates a schematic diagram of a reflection mode instrument. 

LAMMA 1000 and LIMA. These instruments are designed for tasks in principle comparable to those of dynamic SIMS or imaging ion-microprobes. ... 

Figure 2. Schematic diagram of LAMMA 500 instrument, adapted for simultaneous detection of ions and neutrals.

Laser microprobe mass analyzers permit mass spectrometric analysis of very small volumes (0.01-1 pm3) of thin Sections. The method is based on laser induced ion production from a microvolume and analysis of the evaporated ions in a time-of-flight mass-spectrometer. The technique allows detection of all elements and isotopes with a sensitivity approaching the ppm range and an extremely low limit of detection 10 15 to 10-20 g. Transmission type instruments such as the LAMMA 500 are designed for the analysis of particles of 3 pm in diam. The lateral resolution is about 0.5-1 pm. Because the area to be analyzed is selected by an optical microscope, distribution of chemical constituents can be precisely correlated with morphologic structures (Hillenkamp et al., 1982 39), Simons, 198440), Kaufmann, 1984)41 >. 

Thin Sections or pieces of the rock about 1 mm in size or less can be also analyzed with this instrument at glancing incident irradiation, if the site to be analyzed is close to the surface of the section or the edge of a fraction. However in this mode of operation, mass resolution is severely reduced. Nevertheless ions can be identified because of their low mass numbers and the very low background in the spectra, by known cluster patterns or by comparison with reference spectra obtained with reduced laser irradiation. The spectra have shown to be highly reproducible. For more precise bulk. sample analysis, other instruments such as the LAMMA 1000 are more suited. Their lateral resolution is 1-3 pm in diameter and the depth of analysis is typically 0.1 pm. 

This technique has recently been extended to the much more useful reflection mode as the LAMMA 1000 by Leybold Heraeus(18,20) and the LIMA by Cambridge Mass Spectroscopy Co.(21,22) In these Instruments, the region of Interest is located under a microscope. The laser beam is focussed and pulsed through a microscope, producing a plasma that fragments and ionizes the molecules, which are then analyzed in a time of flight mass spectrometer. One of the major parameters to be controlled and measured is the laser power, to get reproducible fragmentation ... 

Another LDI instrument that was similar in principle to LAMMA was developed by Perchalski (1985) that featured the additional selectivity of two stages of mass analysis provided by a triple quadrupole mass spectrometer (QqQ). The LDI QqQ was shown to have potential for use as a probe-type analyzer for molecular analysis of mixtures, as demonstrated by the detection of a mixture of nine antiepileptic drugs by monitoring the precursor ion/product ion pair for each drug (Perchalski et al., 1983). The LDI—QqQ, however, was determined to be too slow to adequately characterize molecules ionized by cationization or anionization after desorption by a single-shot laser. Also, the vaporization/ionization process on the LDI—QqQ was unable to ionize polar, nonvolatile, and/or thermally unstable molecules (Perchalski, 1985). 

Vogt H, Heinen HJ, Meier S, Wechsung R (1981) LAMMA 500 Principle and Technical Description of the Instrument. Fresenius Z Anal Chem 308 195... 

Feigl, P Schueler, B. Hillenkamp, E Lamma-1000, a new instrument for bulk microprobe mass analysis by pulsed laser irradiation. Int. J. Mass Spectrom. Ion Processes 1983, 47, 15-18. 

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