2427then removed by using spectral subtraction. The absorbance of the carbonyl peak in the final spectra is perfectly linear. This indicates that the spectral coaddition method can be reliably used for quantitative measurements.The spectra features necessary for identification of methyl palmitate are visible a t the 10-ng level. With this criterion for an identification limit, this is an MIL of 10 ng.Application. The SFC/FT-IR flow cell interface described here has been used in a variety of applications including the analysis of thermally labile carbamate pesticides (19-21) and natural products (20,22). In each application, FT-IR identification of the eluted components shows high sensitivity for these compounds and provides positive identification to distinguish between related species. LITERATURE CITEDJinno, K. Chromatograph& 1987, 23, 55-62. Shafer, K. H.; Pentoney, S. L.; Grifflths, P. R. HRC CC, J . High Reso-/ut. Chromatogr . Chromatogr . Commun. 1984, 7 , 707-709. Fujimoto. C.; Hirata. Y. H.; Jinno, K. J. Chromatogr. 1985. 332, Shafer, K. H.; Pentoney, S. L.; Griffiths. P. R. Anal. Chem. 1988, 58, Shafer. K. H.; Pentoney, S. L.; Griffiths, P. R.; Fuoco, R. HRC CC, J . High Resolut . Chromatogr . Chromatogr . Commun . 1988. 9 , Pentoney, S. L.; Shafer, K. H.; Griffiths, P. R. J. Chromatogr. Sci. 47-56. 58-64. 168-171. 1988, 24, 230-235. Raynor, M. W.; Bartie, K. D.; Davies, I. L.; Williams, A.; Clifford, A. A,; Chalmers, J. M.; Cook, B. W. Anal. Caude, M.; Richard, H.; Rosset, R. Chromatograph& 1988, Levy, J. M.; Rltchey, W. M. HRC CC, J . High Resolut. Chromatogr. Chromatogr. Commun . 1987, IO, 493-496. Smith, R. D.; Kaiinoski. H. T.; Udseth, H. R.; Wright, B. W. Anal. Chem. 1984, 56, 2476-2480. Snyder, L. R.; Kirkland, J. J. Introduction to Modern UquH Chromatography, 2nd ed.; Wiley: New York, 1979; pp 31-33. Wieboidt. R. C. Ana&& of PestlcHes by Cap//&ry SFC-FTIR; Nicolet FTIR Application Note AN-8705, 1967. Wieboldt, R. C.; Smlth, J. A. I n Supercrltical FluH €xtraction and Chromatography-Techniques and Appiicabns ; Charpentler, B. A., Sevenants. M. R., Eds.; ACS Symposium Series 366 Amerlcan Chem ical Soclefy: Washington, DC, 1988; pp 229-242. Later, D. W.; Bornhop. D. J.; Lee, E. D.; Henion, J. D.; Wieboldt, R. C. Wleboldt, R. C.; Kempfert, K. D.; Later, D. W.; Campbell, E. R., submitted for publication in HRC CC, J. High Resolut. Chromatogr. Chromatogr . Common. 489-495. 535-540. 21, 523-530. LC-GC 1987. 5 . 804-816.The absorptlon propertles of a matrix surrounding an analyte influence the band intenSny In near-lnfrared dmuSe reflectance spectra. I f the matrlx does not absorb radiation at the same wavelength as the analytical band, then use of the Kubelka-Munk equation provldes a linear relationship between band lntenslty and concentration over a major portlon of the concentration range for the analyte. If the m a t h surrounding the analyte absorbs radlatlon at the same wavelength as the analytical band, then deviations from llnearlty of plots of the Kubeika-Munk function versus concentration occur....

An infrared/attenuated total reflection (ATR) technique has been utilized to study the structural changes in proteins induced by nonaqueous solvents, without the need of dissolving the protein in the nonaqueous solvent. For the two proteins studied, methanol and ethylene glycol caused similar changes in albumin, i.e., an increase in helix secondary structure. However, the two solvents had dissimilar effects on immunoglobulin G (IgG). Changes in the pH of aqueous solutions of IgG produced a third effect. By dissolving some IgG in ethylene glycol and then adsorbing IgG from this solution onto an ATR crystal, the time behavior of the adsorption process could be studied and a mechanism for the structural changes proposed.

The mid- and near-infrared diffuse reflection spectra of three carbohydrates—microcrystalline cellulose, wheat starch, and sucrose—are examined to determine whether dilution is necessary in either spectral region in order to avoid the effects of specular reflection. As expected, it was found that dilution was not necessary to obtain valid diffuse reflection spectra of samples in the near-infrared, but that dilution was necessary for measuring mid-infrared diffuse reflection spectra free of the effects of specular reflection. The effects of particle size and sample morphology were investigated for sucrose crystals up to 2 mm in dimension. Depending upon the particle size and orientation, the effects of specular reflection can be observed in both near- and mid-infrared diffuse reflection spectra of sucrose. Surface roughness can allow a diffuse reflection component to be measured in the spectra of very large particles where a specular reflection mechanism would typically be expected to predominate.

Huang for help in NMR analysis, and Drs. K. Bock and B. Meyer for providing the GE-GOP program. This research was supported in part by the NIH (Grant GM44154) and the NSF (Grant CHE8996249).