Evaluation of Kromoscopy: resolution of glucose and urea.
Kromoscopy involves the transmission of a broad band of electromagnetic radiation through the sample of interest. The transmitted light is collected and divided evenly into four detector channels with complementary bandpass functions. This optical configuration provides high signal-to-noise ratios that are ideal for analytical measurements. The molecular basis of the four-channel response is critical, because it directly influences selectivity of the measurement and, therefore, the feasibility of applications in complex sample matrices. Selectivity of the Kromoscopic signal is demonstrated by resolution of glucose and urea with four channels of information collected over the 800-1300-nm near-infrared spectral region. Analysis of the individual channel responses indicates that the displacement of water from the optical path by the dissolution of solute is a major component of the Kromoscopic measurement in this spectral region. Nevertheless, significant differences are observed in channel responses for glucose and urea. A three-dimensional vector plot of the data highlights these differences and reveals unique vector directions for glucose and urea. This difference in direction of the response vectors represents the principal basis for distinguishing glucose and urea dissolved in aqueous solutions.
Helwig
A M
AM
Department of Chemistry and Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242, USA.
Arnold
M A
MA
Small
G W
GW