Evaluation of Kromoscopy: resolution of glucose and urea

Kromoscopy involves the transmission of a broad band of electromagnetic rad iation through the sample of interest. The transmitted light is collected a nd divided evenly into four detector channels with complementary bandpass f unctions. This optical configuration provides high signal-to-noise ratios t hat 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 individ ual channel responses indicates that the displacement of water from the opt ical path by the dissolution of solute is a major component of the Kromosco pic measurement in this spectral region. Nevertheless, significant differen ces are observed in channel responses for glucose and urea. A three-dimensi onal vector plot of the data highlights these differences and reveals uniqu e vector directions for glucose and urea. This difference in direction of t he response vectors represents the principal basis for distinguishing gluco se and urea dissolved in aqueous solutions. (C) 2000 Optical Society of Ame rica OCIS codes: 000.2170, 170.3890, 170.1610, 120.3890, 000.1570.