The long-term reproducibility of a set of water spectra in the infrared region with cell thicknesses of less than 10 mu m was tested. With the application of a computer routine for subtraction in the range from 2600 to 1100 cm-1 and the use of additional phase and nonlinearity corrections, an accuracy better than one milliabsorbance unit (mAU) can be achieved, if the temperature is kept constant within a tenth of a degree or if a temperature correction factor is implemented in the subtraction routine. The subtraction of water from an aqueous protein solution reduces the spectral range for a correction to 2300-1800 cm-1.In this region the protein absorption, as derived from dry protein films, is constant, and because of the association band at 2125 cm-1 water exhibits good subtraction properties. However, the reduction of the spectral range for the water subtraction leads to an increase in the residual error to 12 mAU at 1650 cm-1. This standard deviation can be reduced to 6-7 mAU by applying a second subtraction range from 4000 to 3650 cm-1. A further reduction of this error to 3-5 mAU is obtained by implementing a constant ratio of the integrated intensities of the amide I and amide II bands in the procedure of subtracting water from aqueous protein solutions. The remaining inaccuracy is mainly
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.
Contact your librarian or system administrator
Login to access OSA Member Subscription