| Improved methodology and instrumentation for chemical analysis via low-temperature, time-resolved, laser-excited, multi-dimensional luminescence spectroscopy is presented. The drawbacks commonly associated with conventional liquid nitrogen and liquid helium measurements are circumvented through the integration of a tunable dye laser, a cryogenic fiber optic probe, a spectrograph, and an intensified charge-coupled device (ICCD). By freezing the fiber optic probe directly into the analytical solution, scattered radiation from multiple optical interfaces and interference from bubbling cryogen are eliminated. By retaining the simplicity of "dunking" the sample into the liquid cryogen and the use of an ICCD/spectrograph combination, the process of freezing the sample, data acquisition, and sample cleanup is accomplished in less than five minutes.; The accuracy and precision of this approach is demonstrated for liquid nitrogen and liquid helium measurements. The low-temperature fiber optic probe is well suited for analysis in various matrices. Inhomogeneous frozen solvents and solid substrates are as easily analyzed as Shpol'skii matrices. By incorporating time-resolved fluorescence and phosphorescence in a single instrument, a high degree of specificity is achieved through excitation, emission, and temporal luminescence information. This simple, rapid, and accurate approach makes multi-dimensional, low-temperature analysis attractive as a stand-alone technique or as a support technique for HPLC when a greater degree of specificity is needed. |
