Page 491 - Tandem Techniques
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plates were dried. Small circles of foil were cut from the plate containing the solutes and each was then
treated with a solvent (e.g. dichloromethane) to dissolve the solute.
Figure 12.13
Extraction of Solute and Deposition of Matrix
Extraction was allowed to continue for a few minutes and then the matrix agent was added. The solvent
was then allowed to completely evaporate leaving a solid mixture of the matrix agent and the solute.
A number of different substances were employed as matrix agents including 4-hydroxy-3-
methoxycinnamic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, 3-hydroxypicolinic acid and 2-(4-
hydroxyphenylazo)benzoic acid. The samples were then transferred to a LAMMA 1000 time of flight
mass spectrometer comprising a laser microprobe in conjunction with a nitrogen laser, and post-
acceleration to 1.5 keV onto a discrete dynode type secondary ion multiplier.
The mass spectrometer system included an x/y manipulator and microscope to allow position
adjustment of the sample and visual selection of the position of the laser. The system was found to
provide spectra from as little as 2-4 ng of sample, but this minimum sample size varied somewhat with
the nature of the solute and that of the matrix. An example
