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A novel application of near-infrared (near-IR) spectroscopy for the on-line determination of nanoparticle size of a drug compound in a high solids dispersion is described. The on-line spectroscopic technique provides real-time data for process monitoring and control and overcomes the limitations that are encountered using laboratory-based instrumentation for nanoparticle size determination. Near-IR spectroscopy is capable of providing an accuracy of 2.4 nm near the endpoint of particle production, where the volume-weighted D90 particle size is determined to be 200-220 nm. The accuracy is adequate for endpoint control, which minimizes excess processing and provides control over the particle size throughout nanoparticle production.

Charge transfer excitation at 600 nm of the ion pair [Co(Cp)~+lCo(C0)4-] prepares a neutral pair that can undergo spontaneous electron transfer. Electron transfer rates were measured by picosecond transient IR absorption for quantum numbers of 0 and 1 in the CO stretching mode of the Co(CO)4 species. The rate of electron transfer was 2 times faster with one quantum of energy in the CO stretch mode. The electron transfer returns the ion pair species, and we measured transient IR for levels having 2, 3, and 4 quanta in the ion pair. The rise time of these levels is consistent with the measured rates of leaving the neutral pair. A model calculation was done that shows approximate agreement with the observed ratio of electron transfer rates. This is the first observation of electron transfer rates with vibrational resolution.

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We report novel transient infrared "tag and probe" investigations of the equilibrium kinetics and vibrational energy transfer between the free acid Et 3 SiOH and its 1:1 hydrogen-bonded complex with acetonitrile, Et 3 -SiOH‚‚‚NtCCH 3 , in dilute (0.1 mol/dm 3 acid) CCl 4 solutions at 293 K. Picosecond time-resolved infrared double-resonance spectroscopy measures the vibrational population of the OH-stretching mode (via V ) 1 f 2 absorption) after IR excitation of either the free acid or the homogeneously broadened OH(V ) 0 f 1) absorption of the complex. The free acid and 1:1 complex OH(V ) 1) population lifetimes (T 1 ) and equilibrium reaction rate constants affecting hydrogen-bond formation and dissociation are unambiguously determined for this system. Tagged free acid OH(V ) 1) leads to complex formation with OH(V ) 1) excitation, indicating OH(V ) 1) population is maintained during collision and formation of hydrogen bonds. This is the only known example where OH(V ) 1) vibrational population of a polyatomic reactant is prepared and that excitation is followed during a condensed-phase bimolecular reaction which leads to an excited hydrogen-bonded product. † To Professor Robin Hochstrassersa sincerely dedicated scientist, teacher, and mentor.

Near-infrared (NIR) spectroscopy has become well established in both the pharmaceutical arena and other areas as a useful technique for rapid quantitative analysis of solid materials. Though laser-induced breakdown spectroscopy (LIBS) has not been widely applied in the pharmaceutical industry, the technique has been used for rapid quantitative analysis of solids in many other applications. One analysis amenable to each technique is the determination of magnesium stearate in solids during the lubrication blending unit operation of pharmaceutical processing. A comparative study of the utility of these two techniques for this application will be presented. Necessary sample preparations and the extent and type of matrix effects will be discussed. Additionally, it will be shown that NIR provides better accuracy and precision than LIBS with the experimental parameters used; however, LIBS showed superior selectivity as it was demonstrated to be more robust to sample matrix perturbations. Examples of blending applications will also be presented.

Application and characterization of large-format IR focal-plane arrays as detectors for ultrafast, high-resolution IR spectroscopy are discussed. We also present generation of broadband IR probe-reference pulses by use of collinear non-phase-matched geometry and shot-to-shot dual-track normalization to obtain transient spectra from broadly absorbing hydrogen-bonded systems. As much as 400-cm(-1)-wide coverage with 15-cm(-1) FWHM spectral resolution and +/-6.4 x 10(-4)(DOD = 3 x 10(-4)) baseline standard deviation (+/-1sigmas) is demonstrated near 2.9 microm.